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Monday, July 13
 

8:15am ADT

Registration
Monday July 13, 2026 8:15am - 5:00pm ADT

Monday July 13, 2026 8:15am - 5:00pm ADT
TBA

9:00am ADT

Announcements
Monday July 13, 2026 9:00am - 9:10am ADT

Monday July 13, 2026 9:00am - 9:10am ADT
Ballroom B1

9:10am ADT

Keynote 3: Blake Richards, "Exponentiated gradients support effective learning in biologically relevant scenarios"
Monday July 13, 2026 9:10am - 10:10am ADT
Computational neuroscience relies on gradient descent (GD) for training artificial neural network (ANN) models of the brain. The advantage of GD is that it is effective at learning difficult tasks. However, it produces ANNs that are a poor phenomenological fit to biology, making them less relevant as models of the brain. Specifically, it violates Dale’s law, by allowing synapses to change from excitatory to inhibitory, and leads to synaptic weights that are not log-normally distributed, contradicting experimental data. Here, starting from first principles of optimization theory, I will present an alternative learning algorithm, exponentiated gradient (EG), that respects Dale’s Law and produces log-normal weights, without losing the power of learning with gradients. We show that in biologically relevant settings EG outperforms GD, including learning from sparsely relevant signals and dealing with synaptic pruning. Altogether, our results show that EG is a superior learning algorithm for modelling the brain with ANNs.


Monday July 13, 2026 9:10am - 10:10am ADT
Ballroom B1

10:10am ADT

Coffee break
Monday July 13, 2026 10:10am - 10:40am ADT

Monday July 13, 2026 10:10am - 10:40am ADT
Ballroom Salon

10:40am ADT

FO3: Gene Gradients Reveal Directed Structural Connectivity Across Species
Monday July 13, 2026 10:40am - 11:10am ADT
Benjamin S. Sipes*1, Ashish Raj1

1Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States

*Email: [email protected]

Introduction
Diffusion MRI (dMRI) tractography estimates the brain's white matter structural connectivity (SC) in vivo, but it cannot resolve the directionality of white matter pathways. Yet, much recent work has shown that genes and gene co-expression maps relate to SC across species [1-4]. Here we test whether gene co-expression gradients can infer connection directionality from undirected structural connectivity using the brain’s structure–function relationship.

Methods
We introduce asymmetry to SC (C) via a similarity transform with a node-level gauge parameterized by genetic gradients: C̃=ACA^-1, where A=diag(e^{Ga}), with G=[g_1,...,g_k] genetic gradient vectors and a=[a_1,...,a_k]^T gradient weights. We learn gradient weights by fitting a higher order network diffusion (HONeD) model of the SC graph Laplacian, ℒ=I-C̃D_{in}^-1, f(ℒ)=-κI-βℒ+ξℒ^2, to the residual of the Lyapunov equation, f(ℒ)^TΣ+Σf(ℒ)+I [5,6], with stationary covariance (Σ) estimated from functional neuroimaging. We compared our model's performance to ground truth directionality in three species: C. elegans, mouse, and macaque [7-10]. We then ran our model on 770 HCP subjects [11,12]. Public datasets supplied gene expression [13-17].

Results
Model-predicted directionality significantly correlated with ground-truth directed edges in all three species. Our model predicted neuron-to-neuron synaptic directionality in C. elegans (r=0.56, p<10^-253) and tracer-based directionality in mouse (r=0.57, p<10^-37) and macaque (r=0.46, p<10^-44) (Fig.1a-b). The optimal numbers of genetic gradients was also different in each species (C. elegans: k=3; Mouse: k=5; Macaque: k=1). We found that humans had optimal test-retest reliability when using k=5 genetic gradients (ICC=0.46). Human predicted degree asymmetry suggests that the hippocampus and posterior cingulate are network sources while temporal poles are network sinks (Fig.1c).

Discussion
Although white matter pathways exhibit directionality, estimating their orientation has largely been restricted to tracer-based experiments and a small number of specialized imaging methods. Our results suggest that gene gradients combined with structure–function modeling provide a biologically grounded framework for inferring directed structural connectivity across species, supporting the idea that molecular gradients may encode directional biases in large-scale brain networks. Estimating human SC directionality is valuable not only for basic neuroscience, but also for evaluating circuit-level models of brain function and for studying diseases such as Alzheimer’s, Parkinson’s, and ALS that may propagate along structural pathways [18].

Figure 1. (a) Model-estimated directionality parameters (e^{Ga}) for the three non-human species: C. elegans (top), Mouse (middle), Macaque (bottom). In the C. elegans plot, each dot represents a single neuron. (b) Scatter plots comparing empirical to predicted skew edges with Pearson correlations listed at the top left (all p<10^{-37}). (c) Predicted human overall degree asymmetry for 414 brain regions.
Speakers
avatar for Benjamin Snow Sipes

Benjamin Snow Sipes

Graduate Student Researcher, University of California, San Francisco
My research develops computational approaches for understanding how brain structure shapes neural function. I use graph signal processing, spectral graph theory, and multimodal neuroimaging—including fMRI, diffusion MRI, and MEG—to study structure–function coupling, network... Read More →
Monday July 13, 2026 10:40am - 11:10am ADT
Ballroom B1

11:10am ADT

O9: Low-Dimensional Communication Subspaces Reveal Distributed Information Across Neural Areas
Monday July 13, 2026 11:10am - 11:30am ADT
Farzad Karimi*1,2, Javier G. Orlandi1,2

1Department of Physics and Astronomy, University of Calgary, Calgary, Canada
2 Hotchkiss Brain Institute, University of Calgary, AB, Canada

*Email: [email protected]

Introduction
Recent technological advances allowing us to simultaneously record across thousands of neurons have revealed the presence of distributed representations across the brain [1]. However, the network processes and information pathways that create these distributed representations are still poorly understood. To identify these distributed representations, we measured shared information across brain areas, by introducing a new directed connectivity measure, Reduced Rank Connectivity (RRC). RRC is defined through communication subspaces between neural areas, and by comparing these subspaces we can measure the extent of distributed signals across the brain.

Methods
We analyzed Neuropixels recordings from the Allen Institute from 54 mice performing a go/no-go visual change detection task, focusing on six visual cortical areas (V1, LM, AL, RL, AM, PM), as well as the thalamus (LP) and hippocampus (CA1), across two sessions: active behavior and passive replay [2]. To estimate shared information, we applied Reduced Rank Regression (RRR) [3], which predicts target activity from a low-dimensional subspace of a source population. We define the total predictable target activity as a new connectivity measure, called RRC, and distances between subspaces quantify the similarity of shared information across neural areas.

Results
We applied RRR to cortical and subcortical areas to analyze information flow across all area pairs combinations. We showed that model performance, defined as the squared correlation between predicted and test data, saturated with only a few predictive dimensions. These results identify low-dimensional communication subspaces between neural areas (Fig. 1a). We observed consistent shared information across the visual cortex, while predictability was lower for subcortical areas (Fig. 1b). Connectivity computed using RRR differed significantly from structural connectivity [4] (Fig. 1c). Our results also show that RRC is modulated by the animal’s engagement with the task (active vs. passive).

Discussion
Using RRR on multi-area cortical recordings, we identified robust shared information across visual areas during a discrimination task. RRR performance provides a connectivity measure that captures predictive subspaces rather than coarse averages. The results suggest the presence of low-dimensional communication subspaces between neural areas. Cortical areas can be more easily predicted by their own activity than subcortical areas through these communication subspaces during visual processing. RRC differed from structural connectivity and was modulated by behavioral state.

Figure 1. Low-dimensional communication subspaces define RRC. (a) Prediction performance vs. rank; saturation defines optimal number of ranks and RRC. (b) Average RRC across animals; cortical areas are more predictable than subc
Speakers
avatar for Farzad Karimi

Farzad Karimi

PhD student
Monday July 13, 2026 11:10am - 11:30am ADT
Ballroom B1

11:30am ADT

O10: A mathematical language for large-scale spike recordings from hundreds to thousands of neurons
Monday July 13, 2026 11:30am - 11:50am ADT
Alexandra Busch*,1,2,3, Roberto Budzinski2,4, Lyle Muller1,2,3
1 Department of Mathematics, Western University, London ON, Canada
2 Fields Lab for Network Computation, Fields Lab, Toronto ON, Canada
3 Western Institute for Neuroscience, Western University, London ON, Canada
4  Department of Neuroscience, University of Lethbridge, Lethbridge AB, Canada
Email: [email protected]

Introduction
Recent technological advances now allow simultaneously recording the activity of thousands of neurons while animals engage in cognitive tasks. These datasets can offer an unprecedented window into how the brain computes in real time, but they also challenge existing analytical frameworks. There has been increasing interest in the possibility that coordinated patterns of spikes, such as sequences, may contribute to neural computation [1-3]. However, in contrast to the many methods available for analyzing firing rates, mathematical tools capable of systematically probing spike-time structure at the scale of these next-generation datasets remain limited.

Methods
We introduce a decomposition operator for population spike patterns, termed the multi-sample Discrete Helix Transform (ms-DHT). We derive a generalized inner product that allows the ms-DHT to operate directly on patterns of discrete spikes across thousands of neurons without smoothing. The ms-DHT decomposes these spike patterns into a fixed, interpretable basis, mapping each input pattern to a unique vector that captures the occurrence and timing of every spike (Fig.1). In this representation, distances between spike patterns reduces to the Euclidean distance between their ms-DHT outputs. This distance is invariant to neuron ordering and allows detecting repeating structure ranging from simple spike sequences to complex population motifs.

Results
We demonstrate several applications of the ms-DHT to large-scale datasets. Notably, in dual Utah array recordings from the prefrontal cortex of a macaque monkey performing a virtual reality working memory task, the ms-DHT reveals structured spike motifs that predict specific behavioural errors on single trials - before they occur. Further, applications to spiking network simulations with 10,000 neurons demonstrate that the transform operates effectively at the scale of next-generation neural recordings.

Discussion
The ms-DHT provides a flexible framework for analyzing large-scale spike patterns. By decomposing spiking activity onto a fixed, interpretable basis using a generalized inner product, the ms-DHT produces unique descriptions of population activity even when neurons emit variable numbers of spikes—a setting that has posed a central challenge for analytical approaches. The resulting representation supports multiple analyses, including clustering and decoding of full spike patterns, detecting repeating substructure through specific helix contributions, and sliding-window analyses that trace the temporal evolution of spike patterns across long recordings.

FIgure 1. Decomposing spike patterns. The ms-DHT maps a spike pattern (a) to a unique complex-valued vector (b). Each component encodes the strength (amplitude) and timing (phase) of a basis sub-pattern. (c) Distances between spike patterns reduce to Euclidean distances between ms-DHT outputs, which are invariant to neuron order, ensuring behaviourally relevant clusters do not depend on neuron order.

References
[1] Xie, W., Wittig, J. H., Chapeton, J. I., El-Kalliny, M., Jackson, S. N., Inati, S. K., & Zaghloul, K. A. (2024). Neuronal sequences in population bursts encode information in human cortex. Nature, 635(8040), 935–942. https://doi.org/10.1038/s41586-024-08075-8
[2] Chettih, S. N., Mackevicius, E. L., Hale, S., & Aronov, D. (2024). Barcoding of episodic memories in the hippocampus of a food-caching bird. Cell, 187(8), 1922–1935.e20. https://doi.org/10.1016/j.cell.2024.02.032
[3] Busch, A., Roussy, M., Martinez-Trujillo, J. C., et al. (2024). Neuronal activation sequences in lateral prefrontal cortex encode visuospatial working memory during virtual navigation. Nature Communications, 15, 4471. https://doi.org/10.1038/s41467-024-48664-9

Acknowledgments
This work was supported by NSERC, CFREF, NIH, Neuronex NSF, and Canada Research Chairs Program. A.B. gratefully acknowledges a BrainsCAN studentship and NSERC CGS-D. 


Speakers
AB

Alexandra Busch

PhD Candidate, Western University
Monday July 13, 2026 11:30am - 11:50am ADT
Ballroom B1

11:50am ADT

O11: SEM to Simulation: Bringing Ultrastructural Detail to Multiscale Modeling
Monday July 13, 2026 11:50am - 12:10pm ADT
Cecilia Romaro*1, Matei Coldea2, William W. Lytton3,4, and Robert A. McDougal1,5,6,7,8
1 Department of Biostatistics, Yale School of Public Health, New Haven, CT, United States
2 Yale College, Yale University, New Haven, CT, United States
3 Department of Physiology and Pharmacology & Neurology, SUNY Downstate Health Sciences University, Brooklyn, New York
4 Department of Neurology, Kings County Hospital Center, Brooklyn, New York
5 Department of Biomedical Informatics and Data Science, Yale School of Medicine, New Haven, CT, United States
6 Program in Computational Biology and Bioinformatics, Yale University, New Haven, CT, United States
7 Wu Tsai Institute, Yale University, New Haven, CT, United States
8 Interdepartmental Neuroscience Program, Yale University, New Haven, CT, United States
* Email: [email protected]

Introduction
Just as neuron morphology influences spiking behavior and thus network interactions, so too does the 3D placement of spines affect interaction between spines [1] and thus cellular behavior. However fine spine details are not visible under the optical microscopy used for reconstructing neuron morphology and full-cell scanning electron microscopy (SEM) images are generally not feasible due to size constraints. To address these challenges, we developed a tool for the NEURON simulator [2] for importing and editing an SEM reconstruction of a portion of a dendrite, selecting spines, rotating them, and inserting them into a full-cell reconstruction for simulation, using our experimental support for reaction-diffusion multigridding in NEURON.

Methods
SEM images may be segmented to identify each spine using standard segmentation software then exported to a TIFF stack. We estimate key electrical properties: approximately equivalent length, diameter, volume, and surface area. Our tool loads the image stack and identifies the voxels forming each spine-dendrite boundary so that we can preserve the connection location after transformations. PySide6 is used to provide a graphical interface allowing spines to be selected and manipulated into position; this can also be done programmatically. An algorithm adds/removes voxels to connect the spine cleanly. Transformed spines can be exported to text files for easy editing, enabling iterative refinement.

Results
We present our graphical tool, examples of relevant data sets, and simulation results. The graphical tool allows visualization of both the loaded SEM data and the placed spines after transformations. The simulations leverage our previous work, allowing a synaptic source (e.g., of IP3) to be placed at a precise 3D location within a spine. We validate the multigrid simulation by comparing to a single unified 3D simulation and contrast it to simplified geometry approximations, illustrating their similarities and differences. In particular, our tool allows toggling between the two representations.

Discussion
Support for imported spine morphologies brings NEURON a step closer to capturing the intricacies of the human brain. The same tool described here can also directly be used for incorporating SEM data of a dendrite as well. It is not feasible to simulate full cells and networks at this level of detail, nor is that necessarily desirable -- simpler models are often more useful for insights -- but our approach allows us to explore localized behavior in detail in a multiscale context with full cell and network simulations. This tool can give us insight on which details model when and allow us to explore detailed biological questions of synaptic plasticity or the role of morphological changes in disease.

References

1. Huertas, M. A., Newton, A. J., McDougal, R. A., Sacktor, T. C., & Shouval, H. Z. (2022). Conditions for synaptic specificity during the maintenance phase of synaptic plasticity. Eneuro, 9(3). https://doi.org/10.1523/ENEURO.0064-22.2022

2. Hines, M. L., & Carnevale, N. T. (1997). The NEURON simulation environment. Neural computation, 9(6), 1179-1209. https://doi.org/10.1162/neco.1997.9.6.1179

Acknowledgments
This research was funded by the National Institute of Mental Health, National Institutes of Health, grant number R01 MH086638. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Speakers
Monday July 13, 2026 11:50am - 12:10pm ADT
Ballroom B1

12:10pm ADT

O12: A new platform technology to explore and leverage the computational properties of biological neural cultures
Monday July 13, 2026 12:10pm - 12:30pm ADT
Brett J. Kagan*1, David Hogan1, Andrew Doherty1,  Boon Kien Khoo1,  Johnson Zhou1,  Richard Salib1,  James Stewart1,  Kiaran Lawson1,  Alon Loeffler1,
1Cortical Labs, Melbourne, Australia
2 The University of Melbourne, Department of Biochemistry and Pharmacology, Parkville, Melbourne, 3000, Australia

*Email:[email protected]


Introduction
Neural cultures are increasingly explored to understand the computational properties of neural systems due to the controllability and modifiability of these systems. However, BNNs can only be explored reliably as reliable information-processing systems if inputs are delivered in a temporally and structurally consistent manner. In practice, this requires stimulation with precisely controlled structure, microsecond-scale timing, multi-channel synchronization, and the ability to observe and respond to neural activity in real-time. Existing approaches depend on either depend on low-level hardware mechanisms, imposing prohibitive complexity for rapid iteration, or they sacrifice temporal and structural control, undermining consistency.

Methods
To resolve this problem. We developed a bespoke but scalable system (the CL1)1 that coupled with a easy to use Application Programming Interface ( CL API)2 to  enables real-time, sub-millisecond closed-loop interactions with neural cultures. The system itself provides real-time closed-loop electrophysiology with integrated life support. For the API design approach, the CL API provides users with precise stimulation semantics, transactional admission, deterministic ordering, and explicit synchronization guarantees. This contract is presented through a declarative Python interface, enabling non-expert programmers to express complex stimulation and closed-loop behavior without managing low-level scheduling or hardware details.

Results
The result is a scalable device for interacting with in-vitro neural cell cultures via electrophysiology in a closed-loop real-time environment coupled with an integrated life-support system. The devices are server rack stackable, generating up to 6TB of neural activity data per server rack per day, allowing detailed analysis of electrophysiological data, where each unit can run its own embodied environment. This allows an unparalleled investigation of nearly fully controllable neural systems to explore their dynamics in depth. The flexibility of the Cl1 means that information processing and computation in neural cultures can be explored in many ways, including as reservoir computing, in robotics4, or via games such "Pong"5 or “Doom”.

Discussion
The CL1 system coupled with the CL API offers a scalable system for exploring computational dynamics of biological neural networks. Aside from being possible to set up in traditional cell culture laboratories, these systems can be accessed remotely via the cloud where the cell culture methods are managed either by a dedicated company or by partner laboratory groups. This provides a tool for computational neuroscientists, who might otherwise not be able to access these neural cultures, to explore research questions at scale, with precision, and with rapid iteration loops. It is proposed that this availability will allow computational neuroscientists to be able to explore the dynamics of biological neural systems in way never possible before.

Figure 1. The CL-1 device is scalable desktop device compatible with standard server racks that allows real-time closed-loop interactions with neural cells via an MEA reader. The CL-1 has onboard hardware that interprets simple code via a Python API to allow rapid code development and experimental iterations coupled with a closed-loop perfusion circuit to automatically adjusts gas levels and temperature to

References
1) Kagan, B. J. (2025). The CL1 as a platform technology to l
Speakers
Monday July 13, 2026 12:10pm - 12:30pm ADT
Ballroom B1

12:30pm ADT

OCNS Board Meeting
Monday July 13, 2026 12:30pm - 2:00pm ADT

Monday July 13, 2026 12:30pm - 2:00pm ADT
TBA

2:00pm ADT

FO4: Selective routing of spatial information in dentate granule cells emerges through disparate combinations of synaptic and intrinsic plasticity
Monday July 13, 2026 2:00pm - 2:30pm ADT

Sanjna Kumari*1 and Rishikesh Narayanan1
1 Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bengaluru 560012, India
*Email: [email protected]

Introduction
Granule cells (GCs) in the dentate gyrus (DG) receive grid-like spatial inputs and contextual inputs from the entorhinal cortex, both broadly tuned to multiple spatial locations. Despite this, GCs elicit sparse spatial firing that is confined to single place fields, thus playing a central role in selective routing of spatial information to the hippocampal circuit. The mechanisms behind the transformation of broadly tuned afferent inputs into sparse and location-specific outputs remains unclear. In this study, we ask if there are physiologically relevant plasticity mechanisms that can mediate selective routing of spatial information towards place-cell emergence and spatial remapping, especially when inhibitory synapses are absent.

Methods
We employed morphologically and biophysically realistic models of DG GCs (Kumari & Narayanan, 2024), receiving grid-like and contextual spatial inputs from the entorhinal cortex. We employed a stochastic search paradigm in the plasticity space involving fold-changes in excitatory synaptic strengths, persistent sodium (NaP), hyperpolarization-activated cyclic nucleotide-gated (HCN), and inward rectifier potassium (Kir) conductances. We validated plasticity combinations that achieved one of four functional targets relevant to DG spatial tuning: conversion of silent neurons to place cells, uphold existing place field firing, spatial remapping to a new location, and suppression of spurious place fields to obtain a single place field (Fig 1).

Results
While excitatory synaptic plasticity alone was insufficient to generate valid spatial tuning, conjunctive synaptic and intrinsic plasticity yielded several valid plasticity combinations for all 4 targets (Valid/Total models for 4 targets: 243/142,000, 325/10,000, 139/5,000, 224/50,000). These valid plasticity combinations manifested pronounced heterogeneity across all fold-changes, unveiling plasticity degeneracy where disparate plasticity combinations yielded similar spatial tuning outcomes. Dimensionality reduction analyses revealed low-dimensional structures in intrinsic measurement and parameter spaces of valid models. In contrast, the plasticity space did not manifest strong constraints on plasticity across different components.

Discussion
While inhibitory synaptic inputs have been studied as mechanisms for sculpting spatial tuning, we show that selective routing of information and suppression of off-field firing can be achieved through intrinsic plasticity. Among intrinsic components, we predict the axonal initial segment Kir conductance as the strongest determinant of spatial selectivity. We demonstrate that disparate combinations of concomitant plasticity in excitatory synaptic and intrinsic conductances can mediate the emergence, refinement, and remapping of place fields. We show that co-dependent plasticity in different neuronal components can enable robust yet flexible spatial representations despite heterogeneities in neuronal composition and plasticity mechanisms.

FIgure 1. Medial and lateral entorhinal cortex inputs impinge on a DG granule cell. Disparate combinations of synaptic and intrinsic plasticity (NaP, HCN, Kir channels) achieved one of four targets: convert silent cell to place cell, uphold existing place field, remap, or suppress spurious firing. Our results show that robust and flexible spatial tuning is achievable through plasticity degeneracy.References
Kumari, S., & Narayanan, R. (2024). Ion-channel degeneracy and heterogeneities in the emergence of signature physiological characteristics of dentate gyrus granule cells. J Neurophysiol, 132(3), 991-1013. https://doi.org/10.1152/jn.00071.2024

Speakers
Monday July 13, 2026 2:00pm - 2:30pm ADT
Ballroom B1

2:30pm ADT

O13: A Developmental Ring Attractor Model for the Head Direction System
Monday July 13, 2026 2:30pm - 2:50pm ADT
Shujia Liu*1, 2, Bailu Si1, Michael Herrmann2

1School of Systems Science, Beijing Normal University, Beijing, China
2 School of Informatics, The University of Edinburgh, Edinburgh, UK

*Email: [email protected]

Introduction
Most ring attractor models hard-code and phase-biased translation kernels to obtain a stable activity profile (bump) and velocity-driven shifts [1]. This bypasses a key developmental question: Can these stabilizing and translation kernels self-organize, without any pre-set ring topology, from activity statistics under staged multimodal constraints? The Lateral Mammillary Nucleus--Dorsal Tegmental Nucleus (LMN--DTN) loop implicated in head direction system also lacks developmental constraints. Motivated by synfire chain theory [2] we build a plasticity enabled LMN--DTN model and propose: Spontaneous traveling wave statistics plus staged vestibular/visual constraints can drive the emergence of a ring attractor and path integration.

Methods
We constructed a rate-based LMN--DTN circuit model with 400 neurons in LMN and two populations of 400 direction--velocity conjunctive cells in DTN. LMN follows leaky integrator dynamics with plastic recurrent excitatory connectivity and a fixed long-range inhibitory kernel. DTN to LMN feedback consists of plastic phase-biased weights gated by the angular velocity input. Training proceeds in functional stages: We first obtain stable traveling wave statistics without external velocity or vision, then update connectivity via STDP-like and structural plasticity, and subsequently introduce long-range inhibition and a visual teacher for representational stabilization and gain

Results
With random sparse connectivity, no external velocity input, and no hand-designed ring topology templates, LMN networks spontaneously produce a stable unidirectional traveling wave under the joint action of dominant refractory-like neuronal dynamics and global inhibition, exhibiting consistent phase progression (Fig. 1A). STDP-like and structural plasticity then consolidate the temporal correlations into locally enhanced recurrent excitation (Fig. 1B); long-range inhibition transforms the traveling wave regime into a phase-selectable single bump state. Visual relearning markedly improves short-term angle tracking, yet cumulative drift persists during pure path integration after removing visual information (Fig. 1C).

Discussion
Our results indicate that stabilizing and translation kernels of ring attractors need not be hard-coded: intrinsic recurrent dynamics can provide a directional temporal scaffold, which activity-dependent plasticity, staged inhibition, and multimodal constraints shape into a stable bump representation and a learnable translation kernel. Although residual drift remains after visual removal, it is structured rather than arbitrary, suggesting that the model captures much of the required computation while revealing imperfections in the learned kernel. This makes the framework useful both as a proof of principle for de
Speakers
Monday July 13, 2026 2:30pm - 2:50pm ADT
Ballroom B1

2:50pm ADT

O14: How synchronization, excitability, and variability shape CPG rhythmic bursting sequences across different time scales
Monday July 13, 2026 2:50pm - 3:10pm ADT
Pablo Sanchez-Martin*1, Alicia Garrido-Peña1, Irene Elices1, Carlos Garcia-Saura1, Rafael Levi1, Francisco B. Rodriguez1, Pablo Varona1 

1Grupo de Neurocomputación Biológica (GNB), Department of Computer Engineering, Universidad Autónoma de Madrid, Madrid, Spain

*Email: [email protected]

Introduction
Rhythmic sequential activity is present in many nervous systems. Neural circuits that generate this activity usually involve intrinsic neuronal variability and different synapse types [1]. Sequential rhythms often require coordination at different time scales to adapt to specific conditions, or to adjust speed and timing to meet functional needs. Previous studies in computational models have assessed how synchronization and excitability can modulate cycle-by-cycle sequential dynamical invariants [2,3]. In this study, we analyzed the interplay among neural synchronization, excitability, and variability to understand how they are related to the sequentiality timing in CPG rhythms.

Methods
We acquired long recordings of pyloric CPG neurons of  Carcinus maenas  and extracted the spike timings from intracellular and extracellular time series followed by calculation of all sequence intervals between the PD neurons and the LP. We used metrics of synchronization between the electrically coupled PDs (Victor-Purpura distance, Euclidean distance), excitability for all three neurons (Spike Density Function -SDF-, average ISIs), and interval variability. We identified dynamical invariants in the form of relationships between specific intervals and the instantaneous period. To find relationships between these metrics, we performed analysis at three time scales: whole experiment, segments inside experiments, and cycle-by-cycle analysis.

Results
We observed a high level of variability for synchronization, excitability, and the intervals in this system. Ranking each experiment for all metrics revealed a relationship between the variability in the period, the neurons’ SDF, and the strength of the dynamical invariant relationship. Segmenting the data, we found that, in addition to these relationships, synchronization in the PD neurons is related to their excitability. We found non-linear relationships between the excitability of all neurons and their period variability and dynamical invariants. Excitability changes in any neuron were related to the other neurons' excitability at each cycle, although other relationships present at larger time scales were not preserved cycle-by-cycle.

Discussion
It is still unclear how robustness and flexibility can be autonomously balanced in neural sequences. Previous works have found evidence that suggests that connectivity asymmetry, i.e., the presence of both slow and fast synapses, could be responsible for the emergence of coordination rules such as sequential dynamical invariants [2, 3]. The LPPDdelay interval and instantaneous period are related cycle-by-cycle, as well as the excitability of all neurons among them. In an intermediate scale, the excitability is non-linearly related to synchronization, variability and strength of the dynamical invariants. In a larger time scale, excitability, variability, and the strength of dynamical invariants are all related, but not synchronization.

References
[1] Selverston, A. I., Rabinovich, M. I., Abarbanel, H. D., Elson, R., Szücs, A., Pinto, R. D., ... & Varona, P. (2000). Reliable circuits from irregular neurons: a dynamical approach to understanding central pattern generators. Journal of Physiology-Paris, 94(5-6), 357-374. 
[2] Berbel, B., Latorre, R., & Varona, P. (2025). Theoretical bases for the relation between excitability, variability and synchronization in sequential neural dynamics. Neurocomputing, 645, 130218. 
[3] Elices, I., Levi, R., Arroyo, D., Rodriguez, F. B., & Varona, P. (2019). Robust dynamical invariants in sequential neural activity. Scientific Reports, 9(1), 9048. 

Acknowledgments
Research funded by grants PID2024-155923NB-I00, PID2023-149669NB-I00 and CPP2023-010818 (MCIN/AEI and ERDF- "A way of making Europe"). 


Speakers
PS

Pablo Sanchez-Marti­n

PhD Student, Autonomous University of Madrid
Monday July 13, 2026 2:50pm - 3:10pm ADT
Ballroom B1

3:10pm ADT

O15: Exact mathematical description of computation with transient spatiotemporal dynamics in recurrent neural networks
Monday July 13, 2026 3:10pm - 3:30pm ADT
Roberto Budzinski1,2,#, Alexandra Busch2,3,4, Luisa Liboni2,5, Ján Mináč2,3, Lyle Muller2,3,4
1 Department of Neuroscience, University of Lethbridge, Lethbridge AB, Canada
2 Fields Lab for Network Computation, Fields Lab, Toronto ON, Canada
3 Department of Mathematics, Western University, London ON, Canada
4 Western Institute for Neuroscience, Western University, London ON, Canada
5 King's University College at Western University, London ON, Canada
# [email protected]

Introduction
Networks throughout physics and biology use spatiotemporal dynamics for computation [1]. In neural systems, waves of neural activity have recently been shown to shape spiking responses, gate perception, and influence behaviour [2]. However, it remains unclear how network connectivity gives rise to neural dynamics and how these dynamics support computation. To address this question, we introduce a new type of recurrent neural network that admits an exact mathematical solution [3,4], enabling us to directly relate network structure to emergent dynamics and the computations those dynamics perform.

Methods
We introduce a nonlinear recurrent neural network in which each unit is modeled as a complex-valued oscillator. This complex-valued recurrent neural network (cv-RNN) admits a closed-form solution given by an exact propagator. Importantly, this framework introduces a unified matrix representation of the system that encodes the network's connectivity, including connection strengths and delays, and the input. The exact mathematical solution allows us to control the network dynamics, down to the fine-scale pattern of connectivity, allowing us to use the spatiotemporal patterns that emerge for dynamics-based computation in a wide range of tasks [3,4].

Results
We find the cv-RNN can perform a wide range of tasks, including working memory, logic operations, sequence processing, and computer vision, while remaining precise and interpretable mathematically [3,4]. The analytical framework reveals the mechanisms underlying each computation. By exploiting traveling-wave dynamics, the network performs image segmentation and generalizes across different datasets using the same recurrent weights [4]. Further, we create a bio-hybrid version of our cv-RNN, where we leverage patch-clamping techniques to link biological neurons to the recurrent layer, where these neurons can decode the network’s spatiotemporal dynamics and implement computations [3].

Discussion
These results demonstrate that structured spatiotemporal dynamics can serve as a powerful computational substrate in recurrent neural networks. The exact solution links connectivity, input, and emergent dynamics within a unified operator framework. This approach provides a principled way to understand how neural circuits may compute through traveling waves and network dynamics. More broadly, it establishes a general framework for connecting network structure, emergent dynamics, and computation, offering new tools for interpreting biological neural activity and for designing transparent dynamical models in artificial intelligence.

References
[1] Ermentrout et al. (2001), "Traveling electrical waves in cortex: insights from phase dynamics and speculation on a computational role”, Neuron 29, 33.
[2] Muller et al. (2018), “Cortical travelling waves: mechanisms and computational principles”, Nature Reviews Neuroscience 19.
[3] Budzinski et al. (2024) “An exact mathematical description of computation with transient spatiotemporal dynamics in a complex-valued neural network, Communications Physics 7.
[4] Liboni et al. (2025), “Image segmentation with traveling waves in an exactly solvable recurrent neural network”, Proceedings of the National Academy of Sciences 122.
Acknowledgments
This work was supported by NSERC, CFREF, NIH, Neuronex NSF, and Canada Research Chairs Program.


Speakers
avatar for Roberto Budzinski

Roberto Budzinski

University of Lethbridge
Monday July 13, 2026 3:10pm - 3:30pm ADT
Ballroom B1

3:30pm ADT

O16: The role of cell types in critical neural activity
Monday July 13, 2026 3:30pm - 3:50pm ADT
Adrián Ponce-Alvarez*1,,2,3 and Germán Sumbre4
1 Departament de Matemàtiques, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain.
2 Institut de Matemàtiques de la UPC - Barcelona Tech (IMTech), Barcelona, Spain.
3 Centre de Recerca Matemàtica, Barcelona, Spain.
4 Institut de Biologie de l’ENS (IBENS), Département de biologie, École normale supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France


*Email : [email protected]

Introduction
Neuronal activity shows statistics consistent with a critical point, a regime that maximize information capacity. Yet, the role of different cell types remains largely unexplored. Models [1] and in vitro studies [2] suggest that excitation–inhibition (E/I) balance is key for self-organized criticality, but how E and I dynamics interact during in vivo critical activity is unclear. Similarly, glial cells such as radial astrocytes (RAs) regulate neuronal function [3], but their role in criticality is unknown. Here, we studied how E/I neuronal activity and astrocyte calcium dynamics contribute to criticality by combining transgenic zebrafish with cell-type-specific calcium indicators, a stochastic network, and model inference.

Methods
Spontaneous neuronal activity in the optic tectum (OT) of 10 zebrafish larvae was recorded using light-sheet microscopy. A double-transgenic line expressing GCaMP6f in all neurons and Vglut in glutamatergic neurons identified of E and I cells. Two-photon calcium imaging was performed in 7 larvae expressing GCaMP6f in neurons and RCaMP1b in RAs [3]. OT activity was recorded during spontaneous activity and after mild electrical stimulation, which triggered synchronized Ca²⁺ transients in RAs.
E and I activity was modelled using a stochastic network displaying critical avalanches at a E/I phase transition [1]. The maximum entropy principle mapped neuronal activity onto statistical models [4], quantifying criticality and detecting deviations.

Results
Our results show that neuronal avalanches approached criticality when E and I activity were balanced. Notably, the model accurately captured the observed avalanche statistics and their sensitivity to E/I fluctuations around a critical point defined by balanced excitatory and inhibitory synaptic strengths, where balanced amplification drives network avalanches. Furthermore, we found that RA synchronization shifted tectal neuronal activity away from its spontaneous critical state toward a more ordered regime, with a reduced repertoire of network states and diminished susceptibility to external inputs. These findings demonstrate that glial activity can actively regulate the state of neuronal ensembles, including their proximity to criticality.

Discussion
Extensive research highlights the benefits of E/I balance and critical dynamics. Balanced networks enhance amplification, selectivity, and stability, while critical dynamics optimize information processing. Here, we show that neuronal avalanche statistics and their dependence on spontaneous E/I fluctuations in the zebrafish OT match a model reaching criticality at balanced E and I couplings. Moreover, RA synchronization in the OT reshapes collective neuronal activity, consistent with a shift from spontaneous critical dynamics to a more ordered subcritical regime. Our findings show that radial astrocyte activity can shift the state of neuronal ensembles and modulate their proximity to criticality.

References
1.     Benayoun, M., et al. (2010). Avalanches in a Stochastic Model of Spiking Neurons. PLoS Comput Biol, 6(7), e1000846. https://doi.org/10.1371/journal.pcbi.1000846
2.     Shew, W.L., et al. (2011). Information capacity and transmission are maximized in balanced cortical networks with neuronal avalanches. J Neurosci., 31(1), 55-63. https://doi.org/10.1523/JNEUROSCI.4637-10.2011
3.     Uribe-Arias, A., et al. (2023). Radial astrocyte synchronization modulates the visual system during behavioral-state transitions. Neuron 111, (24), 4040-4057.e6. https://doi.org/10.1016/j.neuron.2023.09.022
4.     Tkačik, G., et al. (2014). Searching for Collective Behavior in a Large Network of Sensory Neurons. PLoS Comput Biol, 10(1), e1003408. https://doi.org/10.1371/journal.pcbi.1003408

Acknowledgments
This study was supported by the Project PID2022-137708NB-I00 funded by MICIU/AEI /10.13039/501100011033 and FEDER, UE. A. Ponce-Alvarez was supported by a Ramón y Cajal fellowship (RYC2020-029117-I) funded by MICIU/AEI/10.13039/501100011033 and “ESF Investing in your future”. G. Sumbre was supported by ERC CoG 726280.


Speakers
avatar for Adrián Ponce-Alvarez

Adrián Ponce-Alvarez

postdoc, Polytechnic University of Catalonia
Monday July 13, 2026 3:30pm - 3:50pm ADT
Ballroom B1

3:50pm ADT

Coffee break
Monday July 13, 2026 3:50pm - 4:20pm ADT

Monday July 13, 2026 3:50pm - 4:20pm ADT
Ballroom Salon

4:20pm ADT

Poster Session 2
Monday July 13, 2026 4:20pm - 6:20pm ADT

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P049: Extracellular dipole and quadrupole fields from axonal branching patterns
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
While the fields of extracellular neural recordings are well understood and mostly dominated by the somatic spikes and dendritic activity [1,2], there are some unnecessarily neglected sources. One of these is axonal branching patterns, that can under correct circumstances make a large contribution extracellularly to both near and far fields. These circumstances include, e.g., a synchronous volley of spikes in a branching axonal bundle, as often observed in the auditory brainstem [3]. I address the question under which circumstances the fields from axonal branching patterns can be non-negligible, and whether their fields are fully explained by their dipole contribution.

Methods
I simulate single multi-compartment cells with NEURON and LFPy packages to study their extracellular potentials at distances relevant for EEGs, often referred as far fields. I furthermore analytically study the extracellular fields of axonal branching patterns, singling out their relative dipole and quadrupole contributions to the extracellular field both along and perpendicular to the dipole axis.

Results
As expected, the simulations show that the dipole between apical dendrites and the soma can determined the extracellular far fields in pyramidal-like cell morphologies. Additionally, both the simulations and the analytics show that axonal branching patterns can create similarly extracellular far fields that are similarly large in amplitude. Furthermore, these axonal fields cannot be explained by the dipole contribution alone.


Discussion
As conventionally assumed, the dipole spanned between the dendrites and soma is the main source of the electro-encephalography (EEG) signals of cortical pyramidal neurons [e.g. 4]. This assumption does not necessarily hold for neurons with a large axonal branching zone, particularly when embedded in a population of neurons with similar morphologies and with synchronous population activation. These results have consequences e.g. for the interpretation of evoked somatosensory potentials, such as the auditory brainstem response.

References
  1. Gold, C., et al. (2006). On the origin of the extracellular action potential waveform: A modeling study. 95(5), 3113–3128. https://doi.org/10.1152/jn.00979.2005
  2. Næss, S., et al. (2021). Biophysically detailed forward modeling of the neural origin of EEG and MEG signals. NeuroImage, 225, 117467. https://doi.org/10.1016/j.neuroimage.2020.117467
  3. McColgan, T., et al. (2017). Dipolar extracellular potentials generated by axonal projections. eLife, 6, 343. https://doi.org/10.7554/eLife.26106
  4. Neymotin, S. A., et al. (2020). Human Neocortical Neurosolver (HNN), a new software tool for interpreting the cellular and network origin of human MEG/EEG data. eLife, 9, e51214. https://doi.org/10.7554/eLife.51214



Acknowledgement
I thank Catherine Carr, Christine Köppl, Richard Kempter and Ghadi El Hasbani for helpful discussions, and Hannah Schultheiss for preliminary modeling.
This research was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) grant nr. 502188599.
Speakers
avatar for Paula Kuokkanen

Paula Kuokkanen

Principal Investigator, Humboldt-Universitaet zu Berlin
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P050: Fano-like information filtering profiles in coupled neuronal models.
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Subthreshold dynamics play a key role in spike generation, and it is well-known that some neurons exhibit a frequency preference when integrating subthreshold input– so-called resonators [1,2]. It has been shown, however, that despite the existence of subthreshold resonance, a single resonator neuron exhibits low-pass, i.e., monotonic, information filtering (as measured by the spectral coherence). In other words, in the subthreshold regime, band-pass impedance does not translate to band-pass information filtering. Instead, nonlinearities, such as spiking dynamics, are needed to create band-pass information transfer [3,4].


Methods
Here, we study a similar question in electrically and synaptically coupled pairs of neurons. Our goal is to evaluate whether this resonance profile imparts non-trivial information filtering capabilities to the coupled systems. We numerically simulate an integrate-and-fire coupled to a resonate-and-fire system in both the subthreshold and suprathreshold regime, and we investigate the stimulus-response spectral coherence function of the system under perturbation by coloured noise (Ornstein-Uhlenbeck process), as well as the lower bound of mutual information rate.


Results
With an electrical coupling between a resonator and an integrator, we show that a Fano-like resonance profile appears in the impedance, i.e., a narrow, asymmetric peak with anti-resonance [5]. Moreover, we observe that the coherence function is non-monotonic, with a minimum around the frequency of the opposite neuron. We also find that with a synaptic-like coupling, a similar Fano-like peak appears in the coherence function, and the lower bound of mutual information rate is generally higher.


Discussion
This challenges the claim that neurons require nonlinearities to relay bandpass information filtering properties. This also gives rise to a new type of coherence function and superior information transmission rate overall. This new perspective places information filtering in the context of connection motifs where a small number of resonators and integrators interact, rather than the context of individual neurons.


References
[1] Izhikevich, Eugene M. Dynamical systems in neuroscience. MIT press, 2007.
[2] Izhikevich, Eugene M. "Resonate-and-fire neurons." Neural networks 14.6-7 (2001): 883-894.
[3] Lindner, Benjamin. "Mechanisms of information filtering in neural systems." IEEE Transactions on Molecular, Biological and Multi-Scale Communications 2.1 (2016): 5-15.
[4] Blankenburg, Sven, et al. "Information filtering in resonant neurons." Journal of computational neuroscience 39 (2015): 349-370.
[5] Joe, Yong S., Arkady M. Satanin, and Chang Sub Kim. "Classical analogy of Fano resonances." Physica Scripta 74.2 (2006): 259.

Acknowledgement
I would like thank Prof. Serge Gauvin for the initial inspiration. 

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P051: Stimulation Induced Effects on the Collective Dynamics of a Recurrently-Connected Excitatory-Inhibitory Network
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction


Electrical stimulation has been used as a treatment of a variety of neurological disorders, including Parkinson’s Disease (PD) [1]. Despite its efficacy, its mechanism of action on the modulation of network-level dynamics to alleviate symptoms is not fully understood. Previous computational work has addressed stimulation effects at the cellular and synaptic level, but the underlying collective dynamics and their functional roles remain relatively unexplored [2]. This requires clinicians to rely on manual programming to determine the therapeutic effect [3]. A mechanistic understanding of stimulation effects on the neuronal circuitry is necessary for the development of closed-loop stimulation techniques that could improve patient outcomes.

Methods
Using a sparse, recurrently connected excitatory-inhibitory (E-I) network of leaky integrate-and-fire neurons, we extend the Brunel architecture [4] with short-term synaptic plasticity (STP) [5] and characterise its effects on the original network and changes in the canonical activity states (Fig 1A).
Using an implementation of deep brain stimulation (DBS) that aligns with experimental observations like axonal depolarisation [6], somatic suppression [7], and efferent activation [8] (Fig 1B), we examine the effects of stimulation across the parameter space of E-I balance and external drive. We capture the effect of stimulation on individual neurons and the population-level activity through metrics such as desynchronisation and regularisation.

Results
A known biomarker for PD is the presence of abnormally strong oscillations in the beta band (13-30 Hz) [9]. To model the effects of stimulation on PD treatment, we measured the reduction of the beta-band oscillatory activity, correlated with alleviation of PD-associated motor symptoms [10]. High-frequency stimulation has a strong effect on suppressing strong beta-oscillations in networks receiving low external drive and having a high level of inhibition (Fig 1C, D). Using measures of criticality, we show that the presence of strong beta-oscillations is linked to the network going through a phase transition. Introduction of electrical stimulation prevents this transition from occurring, thereby preventing the pathological oscillatory state. 

Discussion
Our findings show that metrics of criticality can be an effective biomarker for therapeutic efficacy, indicating a transition away from a pathological state. Using this in addition to the power spectral density can allow better control of clinical protocols. We provide a framework for evaluating the effect of stimulation on the collective dynamics of the network across connectivity regimes and activity states to predict behaviour in biologically realistic circuits. We hope to extend this work to computational models of the basal ganglia and hippocampus: two well-utilised sites of high-frequency stimulation [11, 12], to investigate the effect of electrical stimulation on their activity and the mechanisms of action of clinical therapies.

Figure 1. A: Schematic of the network architecture. A subset of the excitatory population is the target of stimulation. B: Schematic of the stimulation model. C: The firing rate, regularity, synchrony, and beta-band power across the parameter space for baseline (left) and 130 Hz stimulation (right). D: The effect of stimulation on metrics of therapeutic efficacy

References
  1. https://doi.org/10.1016/b978-0-444-53497-2.00010-3 
  2. https://doi.org/10.1038/s41582-018-0128-2.
  3. https://doi.org/10.1001/archneur.63.9.1266 
  4. https://doi.org/10.1023/A:1008925309027
  5. https://doi.org/10.1162/089976698300017502
  6. https://doi.org/10.1016/j.expneurol.2008.11.024 
  7. https://doi.org/10.1093/brain/awh616 
  8. https://doi.org/10.1523/jneurosci.23-05-01916.2003 
  9. https://doi.org/10.1152/jn.00697.2006
  10. https://doi.org/10.1002/mds.22419
  11. https://doi.org/10.1016/j.baga.2011.05.001
  12.  https://doi.org/10.1038/nature15694

Acknowledgement
I wish to acknowledge everyone in the Neural Systems & Brain Signals Processing Lab and Krembil Computational Neuroscience for their help and support, especially David Crompton, Xiangyu Ma, and Zoe Paraskevopoulos. I also want to acknowledge CIHR and NSERC for their funding for my doctoral research.
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P052: Recurrent Inhibition Drives Frequency-Selective Deep Brain Stimulation Efficacy via Bistability and Hopf Bifurcation in a Continuous Attractor Network
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
DBS alleviates Parkinsonian symptoms at high frequencies (>90 Hz) yet worsens them at low frequencies (<60 Hz) across STN, GPi, VIM, and SNr; no mechanism explains why frequency alone reverses outcome [1,2]. Pathological beta-band (13–30 Hz) synchronisation in the basal ganglia–thalamocortical loop is the hallmark of Parkinson's disease (PD); its suppression is the leading hypothesis for DBS efficacy [2,3]. High-frequency DBS depresses glutamatergic over GABAergic terminals, shifting E/I balance toward inhibition — an asymmetry attenuated at low frequencies [4,5]. We present a bi-population CANN [6,7] that unifies bistability, beta oscillations, spectral criticality, and spatial responses in a single tractable framework.


Methods
E and I populations sit on a periodic ring with exponential connectivity and ReLU transfer functions [6,7]. DBS is a periodic pulse train; glutamatergic drive scales as F(f) = max(1 + βf, 0), β < 0, the linearised Tsodyks–Markram depression [8]. GABAergic terminals receive a fixed fraction η without attenuation, encoding differential terminal depression [4]. Under uniform stimulation the network reduces to coupled ODEs with Jacobian eigenvalues λ₁,₂ = α ± iω₀ around the active fixed point. Spatial profiles use Fourier decomposition and a Green's function with exact ring boundary conditions. Stochastic fluctuations enter via the linear noise approximation.

Results
Attenuating excitatory drive produces a boundary equilibrium bifurcation at f_th ≈ 90–140 Hz, matching the clinical therapeutic window [1]: below f_th, bistability and hysteresis coexist; above it, excitatory firing is suppressed while inhibitory output grows linearly with frequency, explaining the paradoxical GABAergic increase [4,5]. Beta oscillations emerge when Δ < 0 and α > 0; the Hopf boundary depends only on intrinsic parameters and is invariant to DBS frequency. The spectral criticality index C = ω₀/(2|α|) diverges as α → 0⁻, providing a real-time LFP biomarker for pathological synchrony. Mean-field theory agrees with simulation (N = 100 per population) quantitatively across 1–200 Hz (Fig. 1).

Discussion
DBS therapy and PD pathology act through distinct bifurcations — fully decoupling therapeutic from pathological mechanisms — explaining why DBS is effective without resolving the underlying circuit vulnerability. Testable predictions include: frequency-ramp hysteresis; slope discontinuity in the inhibitory rate–frequency curve at f_th; pre-symptomatic spectral narrowing; nucleus-specific spatial footprints scaling with axonal reach; and stronger pre-operative beta power predicting faster therapeutic onset.

Figure 1. Mean-field theory vs. simulation (N=100 per population). (a)-(c) Excitatory rate R(t) over 0-3 s at f=5, 49, 153 Hz (blue); grey dashed: mean-field prediction; rate fluctuates around mean. (e)-(g) Inhibitory rate R'(t) (red), same convention. (d) Mean R and (h) mean R' at steady state vs. DBS frequency (log scale); circles: simulation; grey line: theory.

References
[1] McIntyre, C. C., et al. (2004). Clinical Neurophysiology, 115(6), 1239–1248.
[2] Neumann, W.-J., et al. (2023). Brain, 146(11), 4456–4468.
[3] Brittain, J.-S., & Brown, P. (2014). NeuroImage, 85, 637–647.
[4] Li, J., et al. (2025). Nature Neuroscience, 28, 341–355.
[5] Xu, H., et al. (2025). Nature Communications, 16, 245.
[6] Wilson, H. R., & Cowan, J. D. (1972). Biophysical Journal, 12(1), 1–24.
[7] Amari, S. (1977). Biological Cybernetics, 27(2), 77–87.
[8] Tsodyks, M. V., & Markram, H. (1997). PNAS, 94(2), 719–723.

Acknowledgement
Supported by the Krembil Brain Institute and the Department of Physiology, University of Toronto. Authors thank colleagues at the Krembil Computational Neuroscience group for discussions.
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P053: Decoding decisions from neuronal activity in different animals with canonical correlation analysis
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Recent studies have investigated the geometric similarity of task structure by developing novel approaches to decode of brain states across animals [1,2,3]. The extent to which neuronal representations are similar within an animal at disparate times or between different animals performing the same task is not well understood. Quantifying the representational similarity of brain states will be critical for understanding disorders that involve impairment of neuronal dynamics. Here, we employed canonical correlation analysis (CCA) to quantify similar network states across time and between animals in recordings of rodent anterior cingulate cortex (ACC) during a decision-making task in which an animal must select one of two choices.


Methods
CCA identifies the strongest overlapping patterns between two different datasets by providing correlation coefficients (CCs) ordered by magnitude. These optimal CCs are identical to the singular values of the cross-covariance matrix calculated after orthogonalizing the data via QR decomposition (described in [2]).
We processed multi-unit neuronal recording into a set of fixed-length firing rate time series; each was synchronized to the time that the animal indicated its choice within a trial. CCA was computed for each pair of trials across all recording sessions to obtain CCs from each comparison.



Results
Within- and between- session trial-to-trial recurrence matrices were constructed using the 1st (i.e. the maximal) CC from each CCA comparison.
Using the within-session recurrence matrix for each session, we clustered trials (KMeans; k=2 clusters) and used cluster labels to decode the animal’s choice. Decoding performance for each session was quantified with Dice distance and evaluated via permutation tests against surrogate data from shuffled cluster labels. In 36/52 sessions, this metric indicated choice decoding was better than chance.
Using the within and between-session recurrence matrices, we clustered all trials from all sessions (KMeans; k=2), and choice decoding was better than chance in 30/52 sessions.

Discussion
We used CCA for pairwise trial comparison to align neural data within and between sessions, using these alignments to build trial-to-trial recurrence matrices that reveal representational similarities in neuronal activity. Notably, the successful decoding of choice from these neural metrics demonstrates that rodent ACC network states exhibit a common, low-dimensional structure across different animals.


References
1. Melbaum, S., Russo, E., Eriksson, D., Schneider, A., Durstewitz, D., Brox, T., & Diester, I. (2022). Conserved structures of neural activity in sensorimotor cortex of freely moving rats allow cross-subject decoding. Nature communications, 13(1), 7420.
2. Gallego, J., Perich, M., Chowdhury, R., Solla, S., & Miller, L. (2020). Long-term stability of cortical population dynamics underlying consistent behavior. Nature neuroscience, 23(2), 260–270.
3. Safaie, M., Chang, J., Park, J., Miller, L., Dudman, J., Perich, M. & Gallego, J. (2023). Preserved neural dynamics across animals performing similar behaviour. Nature, 623(7988), 765–771.

Acknowledgement
This work was supported by grants to CCL from NIH (AA029970, AA029409).
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P054: Single-cell adaptation makes heterogeneity a dynamic feature of neural networks
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction


Throughout biology, diversity plays an important role in maintaining robustness and stability [1]. The same is true of the brain [2], where recent datasets [3,4] have shown widespread heterogeneity, marking it as an unavoidable component of neuronal composition. While heterogeneity has been linked to stability and increased computational potential [2], recent experiments have shown its loss accompanies pathological states [5], suggesting an important functional role. Despite this, how changes in heterogeneity arise remains unknown. Oftentimes considered to be a static metaparameter resulting from solely genetic disposition, heterogeneity is, in fact, a highly dynamic property of biological networks [3] arising from various sources.

Methods


We endowed a simple network model of excitatory neurons with a candidate mechanism for homeostatic adaptation of neural excitability [6]. Through combined analytical and numerical approaches, we measured the effect of input statistics on the excitability of individual cells and how this translated into changes in network heterogeneity at the population scale.

Results


Our results indicated that, through adaptation, diversity in synaptic inputs promotes heterogeneity in cell-to-cell excitability due to changes in the statistics of presynaptic firing rates and network topology. In contrast, whenever the statistics of synaptic inputs between cells were too similar, the same adaptation mechanism promoted the decline in heterogeneity. Further, we demonstrate that these changes in heterogeneity can coexist with degeneracy in firing rates between neurons, reminiscent of what is observed in cortical neurons [3].

Discussion


We have demonstrated that a degenerate adaptation rule is a viable mechanism for dynamically regulating heterogeneity in an excitatory network. Specifically, we showed that this adaptation can sustain, increase, or decrease diversity. Such “dynamic diversity” is dependent on the input statistics to each neuron, which are manipulated by external stimuli, and the amount of cell-to-cell diversity in the network itself. These results thus form the framework for future investigation into how the statistics that arise in more complex networks may influence the heterogeneity and hence functional capacity and resilience of neuronal networks.

References


[1] Landi, P, et al (2018). Complexity and stability of ecological networks: a review of the theory. Popul. Ecol., 60(4).
[2] Hutt, A, et al (2023). Intrinsic neural diversity quenches the dynamic volatility of neural networks. PNAS, 120(28).
[3] Lee, B R, et al (2023). Signature morphoelectric properties of diverse GABAergic interneurons in the human neocortex. Science, 382(6667).
[4] Braun, E, et al (2023). Comprehensive cell atlas of the first-trimester developing human brain. Science, 382(6667).
[5] Rich, S, et al (2022). Loss of neuronal heterogeneity in epileptogenic human tissue impairs network resilience to sudden changes in synchrony. Cell Rep., 39(8).
[6] Trotter, D, et al (2026). Intrinsic Plasticity Underlies the Malleability of Neural Network Heterogeneity. PRX Life, 4(1).

Acknowledgement
The authors thank Andre Longtin for helpful discussions. 
Speakers
avatar for Jeremie Lefebvre

Jeremie Lefebvre

Associate Professor, University of Ottawa
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P055: Thalamocortical myelination controls cortical states
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Myelin maintains the precise timing and coordination of neural signalling by regulating action potential conduction. Maladaptive myelination disrupts this process and underlies many neurological disorders [1]. We recently showed that cortical demyelination induced by cuprizone, a central nervous system demyelinating drug, shifts cortical excitability and synchrony, leading to motor deficits [2]. However, cuprizone impacts myelinated fibres across the brain, including thalamocortical projections of the internal capsule, an essential yet understudied motor pathway. We propose that demyelination of these pathways impedes thalamic control of cortical states [3] and may contribute more to motor impairments than intracortical dynamics.

Methods
We built a sparsely connected spiking neural network comprising four populations: cortical excitatory and inhibitory neurons, the ventral lateral thalamic nucleus, and the thalamic reticular nucleus. Parameters were fitted to Neuropixels data to generate biophysically realistic yet computationally tractable neuronal responses. Demyelination was simulated by either decreasing axonal conduction velocity or increasing spike propagation failure rate, each scaled to the putative severity of cuprizone-induced damage. Key metrics such as firing rate, firing patterns, and spike correlations were analyzed under both conditions and compared to assess how thalamocortical demyelination alters network excitability and synchrony.


Results
Simulations reveal that decreasing conduction velocity or increasing propagation failure rate significantly impacts thalamocortical network dynamics. That is, demyelination impairs the ability of the thalamus to control cortical dynamics and generates network-wide hypoexcitability and decorrelates spiking activity. These results support our hypothesis that demyelination of thalamocortical pathways contributes to network dysfunction.


Discussion
Our preliminary results suggest that thalamocortical demyelination alters action potential conduction, triggering shifts in network excitability and synchrony that may underlie the motor deficits observed in demyelinating disorders. Investigating demyelination also provides an effective framework for exploring the fundamental role of myelin in neural circuits. Future work will assess how these changes in neural dynamics contribute to motor control impairments, which may provide insight on conditions such multiple sclerosis. These findings highlight the importance of axonal pathways that extend beyond the cortex in understanding how demyelination disrupts neural communication.


References
1. Knowles, J. K., Batra, A., Xu, H., & Monje, M. (2022). Adaptive and maladaptive myelination in health and disease. Nature Reviews Neurology, 18, 735–746. https://doi.org/10.1038/s41582-022-00737-3
2. Gagnon, K., Flora Nunes, G. D., Nettles, D., Nguyen, T., Carter, E. R., Lins, A., Williamson, R., Lefebvre, J., Denman, D., Hughes, E. G., & Welle, C. G. (2025). Myelin supports cortical circuit function underlying skilled movement. bioRxiv. https://doi.org/10.64898/2025.12.23.696289
3. Poulet, J. F., Fernandez, L. M., Crochet, S., & Petersen, C. C. (2012). Thalamic control of cortical states. Nature Neuroscience, 15, 370–372. https://doi.org/10.1038/nn.3035



Acknowledgement
We would like to thank the National Research Council of Canada (NSERC GRANT RGPIN-2017-06662), the Canadian Institute of Health Research (CIHR GRANT NO PJT-156164) and National Institutes of Health (NIH GRANT NS115975) for funding.

Speakers
avatar for Jeremie Lefebvre

Jeremie Lefebvre

Associate Professor, University of Ottawa
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P056: Hippocampus-Inspired Artificial Neural Network Enables Robust Classification under Sparsity: Structured versus Brute-Force Robustness
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
We investigate robustness to structural sparsity in a hippocampus-inspired artificial neural network (OurANN) for image classification. OurANN is composed of functional modules—dentate gyrus (DG), CA3, and CA1—rather than conventional hidden layers (see Figure 1). DG enforces sparse competitive representations, CA3 provides recurrent stabilization, CA1 integrates stabilized activity for readout, and shortcut connections (EC→CA3 and EC→CA1) preserve signal flow under sparse connectivity.

Methods
As a baseline, we use a conventional multilayer perceptron (CANN) with three feedforward hidden layers whose numbers of units match those of DG, CA3, and CA1. OurANN classifier is trained using standard backpropagation (Ref. [1]), ensuring direct comparability with the CANN baseline. Using the MNIST dataset as a controlled benchmark, we sweep the inter-layer connection probability pc from 1.0 down to 0.01 and evaluate robustness using global degradation rates and robustness indices, together with local performance metrics.


Results
In the dense and moderate regimes (pc=1.0 ~ 0.1), OurANN and CANN exhibit nearly identical performance, indicating no intrinsic advantage under weak sparsity. Differences begin to emerge in the sparse regime (pc = 0.1 ~ 0.05), where OurANN shows slower performance degradation, in contrast to the CANN. In the extremely sparse regime (pc = 0.05 ~ 0.01), OurANN exhibits clear and persistent robustness, while CANN performance rapidly collapses.


Discussion
Although CANN robustness can be partially recovered through brute-force scaling of layer size, achieving robustness comparable to OurANN requires substantially increased parameter redundancy. These results distinguish structural robustness in OurANN, arising from hippocampus-inspired architectural organization, from brute-force scaling robustness in CANN, achieved through parameter expansion.

Figure 1. Hippocampus-inspired artificial neural network (ANN). Feedforward: EC (entorhinal cortex) → DG (dentate gyrus) → CA3 and Shortcuts (SCs): EC → CA3 and EC → CA1 and inhibitory backprojection: CA3 → DG. S: subiculum.References
[1] Rumelhart, D. E., Hinton, G. E., & Williams, R. J (1986) Learning representations by back-propagating errors. Nature, 323, 533-536.


Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P057: Input-side Competition Predicts Action Selection and Switching in The Basal Ganglia
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Action selection in the basal ganglia (BG) is often inferred from the mean firing rate (MFR) of the output nucleus, substantia nigra pars reticulata (SNr). Because SNr MFR is ultimately driven by its synaptic inputs, we introduce the competition degree Cd, an input-side indicator that directly quantifies how Direct Pathway (DP) and Indirect Pathway (IP) inputs determine selection among competing channels in a spiking neural network (SNN) (see Figure 1).

Methods
For each channel, Cd = SDP/SIP, where SDP and SIP denote the presynaptic current strengths via DP and IP arriving at SNr, respectively (Ref. [1]). The selected action corresponds to the channel with the largest Cd, providing a cause-and-effect mapping from input-side competition to output-side selection, without relying on SNr MFR readout.

Results
To our knowledge, this is the first quantitative formulation of action selection based on input-side DP/IP competition in a multi-channel BG SNN. Our results further show that shifts in Cd predict channel switching when cortical inputs change, indicating that input-side DP/IP competition mechanistically determines selection and switching in BG.

Discussion
These findings identify the competition degree Cd as a quantitative substrate for linking DP/IP competition to selection and switching in BG. Thus, Cd offers a mechanistic predictor of channel dominance: the selection outcome is not merely read out at SNr, but is determined presynaptically by DP/IP competition upstream of SNr output.

Figure 1. (a) Single-channel BG circuit. Green and red lines represent direct pathway (DP) and indirect pathway (IP) to the output nucleus, SNr, respectively. (b) Three-channel BG SNN. Channels 1-3 represent actions and are shown in orange, purple, and gray, respectively.References
[1] Kim, S.-Y., & Lim, W. (2024) Quantifying harmony between direct and indirect pathways in the basal ganglia; healthy and Parkinsonian states. Cognitive Neurodynamics 18, 2809-2829.


Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P058: Direct Quantification of Stability for Linear Dynamical Systems on Networks
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Stability, the ability of a system to return to a steady state after perturbation, is a fundamental property of dynamics on networks, critical in brain networks with regards to epilepsy for example, and in other contexts ranging from ecological networks to power grids. Despite its importance, existing approaches to stability assessment, such as linear stability analysis based on the dominant eigenvalue of the Jacobian matrix, offer only heuristic insights since they ignore the remainder of the eigenspectrum and do not directly quantify deviation from stability. Moreover, current approaches do not give a full interpretation of how individual nodes or motifs of the network structure contribute to the stability (or lack thereof) of the system.


Methods
Here, we introduce a novel technique for directly quantifying the expected deviation from stability of the network dynamics x(t) as a function of the directed network structure C (with Cji, the connection weight from node j to i) assuming linear dynamics around a fixed point: dx(t) = (I − C)x(t)θ dt + ζ dw(t). Here, the process has reversion rate θ>0, and is driven by uncorrelated noise terms with strength ζ2 (for a multivariate Wiener process w(t)).
Our measure for the deviation from stability, Dst, is computed analytically via a power series expansion of network's weighted, directed connectivity matrix C (building on formulations of the network covariance matrix in this fashion [1,2,3]).

Results
We demonstrate that the deviation from stability Dst directly corresponds to a weighted sum of convergent paired walks on the network (Fig. 1). Our measure explains how dynamics become more stable through small-world transitions to random networks dynamics, which dominant eigenvalues can remain blind to.

Moreover, we introduce novel centrality measures capturing how individual nodes contribute to the network’s deviation from stability as sources and targets, respectively, of the convergent walks in (Fig. 1).

We apply the measure to the Epileptor model [4], efficiently distinguishing spreading and non-spreading seizures, and successfully identifying the susceptibility of nodes to seizure dynamics in terms of their embedding in the network.

Discussion
Our method provides the first full characterisation of how stability in dynamics relates to underlying network structure. This is more complete than heuristics focused on only dominant eigenvalues, and provides the interpretation that stability depends solely on convergent walks in the network. The contribution of individual nodes can also be assessed, as novel meaningful centrality measures.

This approach holds much promise for the study of epilepsy, as demonstrated in early application to the Epileptor model where the required change in excitability of a node to cause seizures was found to be directly related to its contribution to network deviation from stability in our framework, providing a network-based explanation of this sensitivity.

Figure 1. Deviation from stability D_st corresponds to a weighted count of convergent walks on the network C

References
[1] Schwarze, A. C., & Porter, M. A. (2021). Motifs for processes on networks. SIAM Journal on Applied Dynamical Systems, 20(4), 2516–2557.
[2] Barnett, L., Buckley, C. L., & Bullock, S. (2009). Neural complexity and structural connectivity. Physical Review E, 79(5), 051914.
[3] Lizier, J. T., Bauer, F.M., Atay, F., & Jost, J. (2023). Analytic relationship of relative synchronizability to network structure and motifs. Proceedings of the National Academy of Sciences, 120(37), e2303332120.
[4] Proix, T., Bartolomei, F., Chauvel, P., Bernard, C., & Jirsa, V. K. (2014). Permittivity coupling across brain regions determines seizure recruitment in partial epilepsy. Journal of Neuroscience, 34(45), 15009–15021.

Acknowledgement
We acknowledge the use of The University of Sydney’s high-performance computing cluster Artemis and National Computational Infrastructure in generating results.

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P059: Whole-brain effective connectivity from residual-based ridge regression in resting-state fMRI
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Linear predictive models provide a computationally efficient starting point for estimating effective connectivity. However, multicollinearity of fMRI is a major challenge, which may cause overfitting and instability. Previous approaches have used partial conditioning or sparse modelling to reduce overfitting which may exclude relevant predictors [1]. Moreover, low-frequency BOLD signals result in strong autoregression in the timeseries, which dominates the models. In this work, we evaluate – in terms of cross-validated predictability – various approaches to building multivariate autoregressive (MVAR) whole-brain effective network models of fMRI brain activity, which specifically handle their strong multicollinearity and autoregression.


Methods
The HCP rfMRI data were denoised, detrended, and deconvolved [2]. The data were parcellated using the Gordon atlas and analysed as a 333-node whole-brain ROI network. For each node, a first-order univariate autoregressive model was fitted, and its out-of-sample R2 was computed as the baseline. MVAR models were then built incorporating all other sources at the previous time step, to predict both original time series and residuals after subtracting autoregressive components, using ridge-regularised first-order least-squares regression. Model performance was evaluated using the mean out-of-sample R2 across nodes (90% training / 10% testing). The ridge penalty λ with the highest mean R2 was selected.

Results
The problem of collinearity and high dimensionality is highlighted in that MVAR models predicting original time series perform worse than baseline self-predictive models, whether ridge regression is included or not. Improvements were only achieved with models predicting residuals after autoregression, with optimal ridge parameter (λ = 30.0) giving a mean out-of-sample R2 of 0.0347. Using the Yeo 7 modules [3], visual and somatomotor systems exhibited the highest predictability (R2 > 0.0400). Limbic regions showed lower predictability (R2 of 0.00658). The effective connectivity matrix from the residual model exhibits asymmetric directed influences, with modular organisation aligned with the Yeo 17 modules (Fig. 1) [3].

Discussion
The higher predictability of visual and somatomotor regions in the one-step model is consistent with their relatively short temporal windows, which may support rapid perceptual and sensorimotor processing [4]. Within the visual system, the strong links between Visual A and Visual B are also consistent with its hierarchical feedforward and feedback organisation. Visual A appears to pass information to Visual B, while Visual B shows strong coupling with control networks. This may reflect a pathway through which visual information is processed, then activates frontoparietal control network. In contrast, the lower predictability of limbic regions may reflect slower, more internally driven dynamics related to memory and emotion [4].

Figure 1. Connectivity matrix estimated from residual model using ridge regression (λ = 30.0) and reordered by Yeo 17 functional networks. The value at row i and column j represents the predictive weight from source node i to target node j.  Red: positive predictive weights. Blue: negative predictive weights.

References

  1. Valdés-Sosa, P. A., et al. (2005). Estimating brain functional connectivity with sparse multivariate autoregression. Philosophical Transactions of the Royal Society B: Biological Sciences, 360(1457), 969–981.
  2. Smith, S. M., et al. (2013). Resting-state fMRI in the Human Connectome Project. NeuroImage, 80, 144–168.
  3. Yeo, B. T. T., et al. (2011). The organization of the human cerebral cortex estimated by intrinsic functional connectivity. Journal of Neurophysiology, 106(3), 1125–1165.
  4. Gollo, L. L., et al. (2015). Dwelling quietly in the rich club: Brain network determinants of slow cortical fluctuations. Philosophical Transactions of the Royal Society B: Biological Sciences, 370(1668), Article 20140165.

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P060: Biological Reservoir Computing in Modular Human iPSC-Derived Neuronal Networks
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
While human brain mapping characterizes these relationships at the macroscale, advancements in Synthetic Biological Intelligence (SBI) now allow us to investigate them in controllable, human iPSC-derived neural systems [1]. To systematically probe these mesoscale dynamics, we utilized the CL1 platform, which facilitates high-level programmability of in vitro networks, allowing for precise spatiotemporal electrical stimulation and real-time functional readouts. Treating cultures as physical reservoirs, we ask whether enforcing modular connectivity (segregation + integration) enhances separability of neural state trajectories compared with unstructured 2D monolayers, across spatial, temporal, and spatio-temporal classification benchmarks.

Methods
In this work, human iPSC-derived cortical and hippocampal neurons were cultured as 2D monolayers or in 60-module PDMS microfluidic devices enforcing modular connectivity) coupled by a peripheral loop enabling re-entrant paths. Spikes were recorded on CL1 at 25 kHz; stimulation/noise artifacts were removed via waveform PCA + GMM clustering. We tested reservoir encoding with spatial source discrimination, Morse ‘S’ vs ‘O’ sequence decoding, and MNIST driven as 16-channel, 5-step spiking tensors. Spike counts were binned to form state vectors x(t) and decoded by logistic regression with 5-fold CV, against shuffled and test-chip controls.

Results
All biological cultures supported above-chance spatial decoding, but modular devices improved fidelity, with mixed cortical–hippocampal modular networks reaching ~96% median accuracy (Fig.1). Temporal Morse decoding depended on network dynamics: only highly active modular cultures outperformed shuffled controls, while hippocampal monolayers were near chance. For MNIST, monolayers performed poorly, whereas high-activity modular cultures achieved 69–75% median (max 82–88%) accuracy; shuffled and test-chip controls stayed at chance. PCA of reservoir states revealed class-separable manifolds only in real modular data.

Discussion
While physical Reservoir Computing has been demonstrated in non-biological substrates, its validation in human iPSC-derived neural networks remained limited [2]. In this work, we show that human iPSC neuronal cultures can act as robust biological reservoirs, and enforced modular topology functions as a computational regularizer that expands functional dimensionality and supports fading memory for complex spatio-temporal separation. The synergy of biological identity (hippocampal + cortical) and engineered modular connectivity suggests a programmable route to test how structural constraints enable—or impair—computation, with implications for both SBI applications and mechanistic models of dysconnectivity in brain disorders.

Figure 1. Binary classification (all distances). Red: neuronal cultures; cyan: shuffled controls. (B) Morse code: accuracy for letter prediction; X-axis cell type/activity; dark green real, light green shuffled. (C) MNIST: digit-prediction accuracy; same axes/colors; dashed line chance. (D) Cortical 60-module MNIST accuracy vs activity (low/med/high). *p<0.05, **p<0.01, ***p<0.001.


References

1. Kagan, B. J., Kitchen, A. C., Tran, N. T., Habibollahi, F., Khajehnejad, M., Parker, B. J., ... & Friston, K. J. (2022). In vitro neurons learn and exhibit sentience when embodied in a simulated game-world. Neuron, 110(23), 3952-3969.
2. Cai, H., Ao, Z., Tian, C., Wu, Z., Liu, H., Tchieu, J., ... & Guo, F. (2023). Brain organoid reservoir computing for artificial intelligence. Nature Electronics, 6(12), 1032-1039.



Acknowledgement
This work was funded by Cortical Labs Pty Ltd.
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P061: Learning Conduction Delay Distributions from Neural Activity to Study Stability in Delayed Nonlinear Neural Networks
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction


Conduction delays between brain regions play a central role in regulating largescale neural dynamics. Plastic changes in white matter modify said delays, altering network stability, synchronization and gain in nonlinear neural systems [1, 2, 3]. However, most theoretical studies assume either simplified or fixed delay structures, while experimentally measured delay statistics remain difficult to estimate from neural recordings. In this present work, we combine theoretical analysis to study the influence of distributed delays on the dynamics of delayed nonlinear neural networks (DNLNNs), and machine learning to infer delay structure directly from neural time-series data.

Methods

We study DNLNNs using two complementary approaches. First, linear stability analysis and random matrix theory are used to characterize how delay statistics influence a DNLNN’s eigenspectrum [4, 5], from which we can infer the network stability. Second, we develop artificial neural network models capable of learning effective delay distributions from neural activity data. Spiking neural networks (SNNs) [6, 7] are trained to infer pairwise delay matrices from multivariate neuronal time series, which are incorporated in simulations of delayed nonlinear networks in order to reproduce the observed dynamics. The full pipeline is illustrated in Figure 1.

Results

The linear stability analysis shows how delay statistics modify the eigenspectra and thus the stability boundaries of delayed nonlinear neural networks, linking the mean and variance of conduction delays to dynamical transitions of the system. In parallel, the machine learning framework successfully recovers structured delay distributions from simulated neural data and accurately reproduces the resulting network dynamics when incorporated into delayed network simulations.

Discussion

The obtained results suggest that combining theoretical analysis with datacentered inference provides a promising approach for studying delayed neural systems. Learning delay distributions directly from neural recordings can help bridge the gap between experimentally measured neuronal activity and mathematical models of large-scale brain dynamics, offering new tools to investigate the influence of conduction delays on the stability and collective dynamics of
neural networks.

Figure 1. Pipeline for data-driven inference of conduction delays and stability analysis of delayed neural networks. Simulated neural recordings are used to train a spiking neural network that infers a pairwise delay matrix τ. The learned delays are incorporated into delayed neural network models whose spectral properties and stability are analyzed.

References

[1] Lefebvre, J et. al,  Myelin-induced gain control in nonlinear neural networks. Commun Phys (2025)
[2] Sampaio-Baptista, C. & Johansen-Berg, H. White Matter Plasticity in the Adult Brain. Neuron (2017)
[3] Scholz et. al  Training induces changes in white-matter architecture. Nat Neurosci (2009)
[4] Pigani, E. et. al, Delay effects on the stability of large ecosystems. PNAS, (2022). 
[5] Leishman, Q. & Webb, B. A New Approach to Stability of Delay Differential Equations with Time-Varying Delays via Isospectral Reduction (2025).
[6] Sun, P., Wu, J., Zhang, M., Devos, P. & Botteldooren, D. Delay learning based on temporal coding in spiking neural
networks (2024) 
[7] Nicola, W. & Clopath, C. Supervised learning in spiking neural networks with FORCE training. Nat Commun (2017)


Acknowledgement
The authors thank members of the Neurophysics and Nonlinear Dynamics group at the University of Ottawa for helpful discussions.

Speakers
avatar for Jeremie Lefebvre

Jeremie Lefebvre

Associate Professor, University of Ottawa
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P062: Mutual information of time sequences in working memory is maximized by parametric heterogeneity in response adaptation and threshold
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
It is crucial for an animal’s survival to remember the path taken to reach an important area of a new environment. In the weakly electric fish, neurons in a thalamic-like region respond to encounters with new objects in bursts whose intensity depends on the time elapsed between events, a viable strategy to encode spatial information [1]. It was recently shown that, with such adaptive responses, parametric heterogeneity is necessary to accurately recall a sequence of multiple encounters from the latest response [2]. Here, we generalize the result to include working memory (WM) of past adaptive responses and show that variety in adaptation and threshold parameters maximizes mutual information (MI) between responses and time sequences.

Methods
Timing information is encoded in a resource variable x(n) = 1 - exp(-T(n)/τ)(1-βx(n-1)), where T(n) is the time interval between encounters n-1 and n, τ is the resource recovery rate and β is its history dependence. The response during an encounter n has Poisson statistics with a firing rate proportional to the rectified value max(x-s,0), s being a response threshold (RT) under which a cell does not respond (see Fig 1A). We model WM with a mixture of this distribution and a uniform distribution whose weight increases with the time since the original event (see Fig 1B). This is to represent the unavoidable – and necessary [3] – forgetting of past stimuli. We then use stochastic gradient ascent to optimize MI with respect to the parameters.

Results
To quantify the effect of heterogeneity, we look at the number of neurons N necessary to reach 80% of the theoretical MI limit for different numbers of optimized population P and sequence lengths (see Fig 1C). Without WM or RT, the optimized parameters are effectively separated into n different populations. As such, no significant efficiency gain is achieved by increasing P past n. The extra representational capacity of heterogeneous parameters becomes advantageous once WM or RT are available. With or without WM, heterogeneous RT provides a more efficient method to encode time interval sequences, requiring fewer neurons for the same information content. In all cases, heterogeneity offers diminishing returns beyond some value of P.

Discussion
The cases without RT and WM are consistent with previous results which showed that 1 population is optimal when n=1 and that at least n different populations are necessary for n>1 [2]. WM allows for a middle ground between both cases, as recollections of previous responses are essentially a noisier version of the single interval case with redundancy coming from later responses. Heterogeneous RT allows for division of labor: a population which does not activate indicates time intervals are in the area given by x<s. Such silent coding was shown to increase spatial information in the same fish [4]. This stratagem might also be indicative of the power of rectified nonlinearities commonly observed across neural systems in sequence encoding.

Figure 1. Encoding time sequences is more efficient with parametric heterogeneity. (A) Responses of multiple populations of adaptive cells with response threshold. (B) Recollection of past responses (working memory) during event n. (C) Number of cells N necessary to reach 80% of theoretical maximum information content about a sequence of length n for different number of optimized populations P.

References
1. Wallach, A. et al. 2018. A Time-Stamp Mechanism May Provide Temporal Information Necessary for Egocentric to Allocentric Spatial Transformations. eLife 7:e36769. doi:10.7554/eLife.3676
2. Lafond-Mercier, R. et al. 2025. Neural Heterogeneity Enables Adaptive Encoding of Time Sequences. Communications Physics 8(1):504. doi:10.1038/s42005-025-02408-3
3. Georgiou, A. et al. 2021. Retroactive Interference Model of Forgetting. The Journal of Mathematical Neuroscience 11(1):4. doi:10.1186/s13408-021-00102-6
4. Haggard, M., & Chacron, M. J. 2025. Nonresponsive Neurons Improve Population Coding of Object Location. Journal of Neuroscience 45(3). doi:10.1523/JNEUROSCI.1068-24.2024

Acknowledgement
This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) RGPIN/06204-2014 (A.L.) and by the Fonds de recherche du Québec – Nature FRQ B2X/328560 (R.L.M.)
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P063: Shared dynamics between active sensing movements and rate-based sensory sampling in electric fish
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Most forms of sensory sampling are performed actively [1,2]. Uncovering the general principles that underly active sensing is thus important for fully understanding animal behaviour. In particular, active sensing movements are an integral part of behavioural repertoires. These movements are often performed rhythmically, and some hypothesize that their frequencies match the intrinsic neuronal oscillations of primary processing areas, thereby enhancing information transfer [3]. Here, we investigate the coordination between active sensing movement and sensory signals in a pulse-type weakly electric fish.


Methods
We perform a reanalysis of previously published data [4] of freely-behaving fish in sensory isolation. Simultaneous video and electrical recordings allow for a joint analysis of postural and sensory acquisition dynamics. Behavioural classification is achieved by applying t-SNE to the wavelet spectra of the inter-pulse interval time series. During rhythmic behaviour, this time series exhibit two dominant frequency bands, around 0.5 and 1 Hz, for which we extract narrowband signals. Postural modes during these rhythmic behaviour are extracted by principal component analysis. 

Results
By analyzing the pair of narrowband sensory acquisition signals, we find that they exhibit hallmark features of synchronization, including phase slips, where the generalized phase difference jumps by multiples of 2 pi, limit cycles of the phase dynamics on the torus, frequency locking, and a preferred value of the relative cyclic phase.  


Discussion
In this work, we analyze a rhythmic motor behaviour of electric fish where the rate at which sensory samples are acquired is itself modulated at frequencies also appearing in the motor pattern. Moreover, we show that this modulation is comprised of several frequency bands that are coupled through synchronization dynamics. This suggest that a shared dynamical template is applied in both the sensory acquisition and movement dynamics.




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References
1. Schroeder, C. E., Wilson, D. A., Radman, T., Scharfman, H., & Lakatos, P. (2010). Dynamics of active sensing and perceptual selection. Current Opinion in Neurobiology, 20(2), 172–176.
2. Wachowiak, M. (2011). All in a sniff: Olfaction as a model for active sensing. Neuron, 71(6), 962–973.
3. Haegens, S., & Zion Golumbic, E. (2018). Rhythmic facilitation of sensory processing: A critical review. Neuroscience & Biobehavioral Reviews, 86, 150–165.
4. Jun, J. J., Longtin, A., & Maler, L. (2014). Enhanced sensory sampling precedes self-initiated locomotion in an electric fish. Journal of Experimental Biology, 217(20), 3615–3628.

Acknowledgement
This work was funded by the Natural Sciences and Engineering Research Council of Canada under Grant No. RGPIN-2022-0 531 4.

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P064: Complementary roles of neuronal and synaptic adaptation in regulating network stability
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Recurrent connectivity and nonlinearity make neural networks inherently susceptible to destabilization by fluctuating input, yet the brain must maintain a consistent level of stability. Near the edge of chaos, decodable information persists over extended timescales. However, in sparse networks obeying Dale's law, structural balance alone cannot constrain destabilizing eigenvalue outliers [1]. Furthermore, external stimuli can alter stability, especially in nonlinear networks [2]. We hypothesized that two complementary forms of adaptation, spike frequency adaptation (SFA) and short-term synaptic depression (STD), together regulate network stability.

Methods

Results
Only networks with both SFA and STD consistently operated near the edge of chaos even as connectivity parameters varied and external stimulation changed. Networks without dual adaptation were much more likely to be overly stable or highly chaotic as connectivity parameters were varied. During excitatory stimulation, networks with no adaptation or with SFA only became significantly more chaotic [2]. As a consequence of remaining near the edge of chaos, networks with both SFA and STD had the greatest memory capacity.

Discussion
SFA and STD provide complementary stabilizing mechanisms that together maintain near-edge-of-chaos dynamics and maximize memory capacity [2]. Multi-timescale SFA approximates fractional differentiation [3,4], connecting our framework to fractional-order dynamical models. Fractional-order network models distinguish epileptic brain states, and stabilizing their dynamics suppresses seizures in simulation [5]. EEG recordings near the seizure onset zone show power spectral density slope changes consistent with altered adaptation [6], suggesting that adaptation dysfunction may contribute to epilepsy.

References

Acknowledgement
This work was supported by funding from the NIH awarded to B.N.L. (NINDS R01NS129622 and K23NS112339).
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P065: Characterizing Epileptic Brain Dynamics Through Fractional-Order Modelling
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Drug-resistant focal epilepsy often requires identifying the seizure onset zone (SOZ) for resection or neuromodulation, yet objective biomarkers of SOZ excitability remain limited. Neural adaptation across multiple timescales can reshape EEG power spectra and can be parameterized using fractional-order dynamics. We hypothesize that the fractional order (alpha) of a fractional neuronal network model provides an indirect, mechanistically grounded measure of neuronal excitability that can be inferred from macroscopic recordings, with potential utility for SOZ localization [2-4].

Methods
We generated synthetic datasets by simulating a recurrent fractional-order neuronal network in which each neuron included a fractional-order filter implementing fractional differentiation consistent with cortical pyramidal-neuron adaptation [1,2]. Networks were driven by white-noise current input; alpha was varied while all other parameters were fixed. From inputs and network outputs we extracted phase shift, phase-locking value, power spectral density (PSD) slope and band powers, spectral density, and Hilbert-spectrum metrics. We fit regression models relating each feature to α and compared goodness of fit across features.

Results
Across different α values, the PSD slope of the network output showed the clearest and most consistent relationship with α. This trend was roughly monotonic. In contrast, phase-based features and Hilbert-spectrum measures were weaker and more variable. Since a fractional differentiator changes the spectrum as a function of frequency, the changes in PSD slope provide an interpretable link between signal properties and alpha. These results suggest that PSD slope could be a simple surrogate marker for fractional order and, indirectly, for neuronal excitability in EEG-like signals.

Discussion
Spectral slope has been linked to synaptic excitation/inhibition balance and hyperexcitability, and interictal EEG near the SOZ shows flattened PSD slopes consistent with reduced adaptation and increased excitability. Our simulation study suggests that estimating alpha from PSD slope could provide a mechanistically grounded, low-complexity biomarker for SOZ identification. Next, we will apply the α-estimation pipeline to clinical EEG recordings with electrode-level SOZ annotations, evaluating SOZ vs non-SOZ classification performance and robustness across patients and recording states.

References


1.      Lundstrom, B. N., et al. (2008). Fractional differentiation by neocortical pyramidal neurons. Nat Neurosci. https://doi.org/10.1038/nn.2212
2.      Lundstrom, B. N., & Richner, T. J. (2023). Neural adaptation and fractional dynamics as a window to underlying neural excitability. PLoS Comput Biol. https://doi.org/10.1371/journal.pcbi.1010527
3.      Gao, R., et al. (2017). Inferring synaptic excitation/inhibition balance from field potentials. NeuroImage. https://doi.org/10.1016/j.neuroimage.2017.06.078
4.      Lundstrom, B. N., et al. (2021). Low frequency novel interictal EEG biomarker for localizing seizures and predicting outcomes. Brain Commun. https://doi.org/10.1093/braincomms/fcab231

Acknowledgement
No funding was received for this work.
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P066: Variability and Degeneracy In Simulations of Primary Motor Cortex Pyramidal Tract Neurons
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
The layer 5B pyramidal neurons (PT5B) are the final output of the primary motor cortex (M1). They suffer from reduced intrinsic excitability in a Parkinsonian mouse model[1]. There is considerable heterogeneity within the population, with evidence from both electrophysiology and single-cell RNA sequencing[2]. We also suspect there is considerable degeneracy, where multiple configurations of ion channels can produce similar responses. Here, we used data-driven multicompartment models to explore the variability and degeneracy of the PT5B neurons.

Methods

We used BluePyOp to optimize parameters of conductance-based multicompartment neuron models for individual fits to in vitro somatic current clamp data from 133 PT5B healthy control neurons. To explore potential degeneracy, we optimized parameters independently 20 times for the same experimental response to produce an ensemble of neuron models. As perturbations can reveal the underlying differences, we modeled the effects of low dose (20nM) tetrodotoxin (TTX), which inhibits the persistent sodium channel (NaP).

Results
There was substantial variability within electrophysiology (Fig. 1A). Simulations reproduced many features of the voltage traces (Fig. 1B), capturing the excitability of individual neurons and the population, e.g., maximum frequency range in experiments 20.5 – 80.4Hz, and simulation 20.0 – 94.4Hz. Similar voltage traces could be produced with a wide variety of model parameters, with substantial variability in the contribution of calcium and dendritic currents. Simulations of low-dose TTX reductions in NaP conductance revealed a subpopulation of neurons where there was little or no change in excitability, with similar maximum frequencies (33% with less than 1% decrease), and no change in rheobase (77% of models).



Discussion
There was substantial variability in the electrophysiology of PT5B neurons, which can be captured by computational models. The diversity of ion channel genes in single-cell RNA counts suggests the degeneracy seen in computational models is not only the result of the ill-posed inverse problem, but also a biologically relevant feature of the neurons. Degeneracy has been shown to play a role in the survival of invertebrates[3] and may be relevant to varying resistance to Parkinsonism.

Figure 1. Variability of PT5B excitability captured by parameter optimization. Voltage traces of PT5B neurons to current clamp at (160 pA, 320 pA, and 480 pA) (A) Experiments, (B) Simulation. (C) Excitability measures demonstrate the variability seen between cells and the ability of parameter optimization to capture both individual responses (highlighted) and the population distribution.

References

1. Chen, L., Daniels, S., Kim, Y., & Chu, H.-Y. (2021). Cell Type-Specific Decrease of the Intrinsic Excitability of Motor Cortical Pyramidal Neurons in Parkinsonism. The Journal of Neuroscience 41(25), 5553–5565.
2. Yao, Z., Liu, H., Xie, F., Fischer, S., Adkins, R. S., Aldridge, A. I., Ament, S. A., Bartlett, A., Behrens, M. M., Van den Berge, K., Bertagnolli, D., de Bézieux, H. R., Biancalani, T., Booeshaghi, A. S., Bravo, H. C., Casper, T., Colantuoni, C., Crabtree, J., Creasy, H., … Mukamel, E. A. (2021). A transcriptomic and epigenomic cell atlas of the mouse primary motor cortex. Nature, 598(7879), 103–110.
3. Goaillard, J.-M., & Marder, E. (2021). Ion channel degeneracy, variability, and covariation in neuron and circuit resilience. Annual Review of Neuroscience, 44(1), 335–357.































Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P067: Modeling spreading depolarization in neocortical microcircuits
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction

Spreading depolarizations are waves of brief neuronal hyperexcitability followed by prolonged depolarization that propagates through grey matter at a rate of 1–9mm/min. Such waves are associated with multiple neurological disorders, including epilepsy, ischemic stroke, and migraine aura. Neurons are susceptible to SD due to their high energy demand, particularly for restoring ion concentrations after action potentials (APs). Here, we model SD to identify different factors that influence neurons and neuronal populations' vulnerability.


Methods
We build on our prior in vitro model of spreading depolarization[1], with connectivity from Potjans-Diesmann cortical microcircuit (PDCM)[2,3] and O2 sources based on capillaries in human V1. The model was developed in NetPyNE using NEURON/RxD to account for ion concentrations and homeostatic mechanisms, including Na+/K+-ATPase, NKCC1, KCC2, and dynamic volume changes. A 2.0 x 2.3 cm cross-section of the human cortical plate in V1 with immunostaining for CD34 was used to determine capillary locations. Optuna was used to determine both single-cell parameters and synaptic weights to achieve firing rates, synchrony, and irregularity comparable to those of the original PDCM.


Results
We simulated 13,000 neurons representing ~1 mm3 of cortex (layers 2-6). We monitored intracellular and extracellular ion concentrations (Na+, K+, Cl-) and O2. O2 was supplied by 918 capillaries (density: 199.6/cm2; cross-sectional area: 16.7±11.9μm2) identified by immunohistochemistry. SD could occur spontaneously when reducing available O2 to simulate hypoxic SD, or by elevating extracellular K+. Preliminary results suggest that susceptibility to SD varied with layer, with layer IV being the most vulnerable and layer II/III the most resilient. Network connectivity did not directly relate to a neuron’s vulnerability to SD, but those that fired at higher frequencies were more vulnerable.

Discussion

This model explores the roles of network connectivity, neuronal density, neuronal activity, and heterogeneity of O2 supply that affect the susceptibility of SD of individual neurons and cortical layers. Our model also suggests that the distribution of capillaries affects neurons' ability to maintain homeostasis and physiological firing. Neurons closer to capillaries are better able to sustain their activity when O2 is reduced.


References
1. Kelley, C., Newton, A. J. H., Hrabetova, S., McDougal, R. A., & Lytton, W. W. (2022). Multiscale Computer Modeling of Spreading Depolarization in Brain Slices. eNeuro, 9(4). https://doi.org/10.1523/ENEURO.0082-22.2022
2. Potjans, T. C., & Diesmann, M. (2012). The Cell-Type Specific Cortical Microcircuit: Relating Structure and Activity in a Full-Scale Spiking Network Model. Cerebral Cortex , 24(3), 785–806. https://doi.org/10.1093/cercor/bhs358
3. Romaro, C., Najman, F. A., Lytton, W. W., Roque, A. C., & Dura-Bernal, S. (2021). NetPyNE Implementation and Scaling of the Potjans-Diesmann Cortical Microcircuit Model. Neural Computation, 33(7), 1993–2032. https://doi.org/10.1162/neco_a_01400





Acknowledgement
This research was funded by the National Institute of Mental Health, National Institutes of Health, grant number R01 MH086638, with HPC time from NIH S10 award, 1S10OD032417-01, and the Yale Center for Research Computing McClearly cluster. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.


Speakers
avatar for Robert McDougal

Robert McDougal

Associate Professor, Yale University
Looking for a postgrad or postdoc position implementing simulation methods? I'm hiring.I'm an Associate Professor in the Health Informatics division of Biostatistics, and a developer for NEURON and ModelDB. Computationally and mathematically, I'm interested in dynamical systems modeling... Read More →
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P068: A novel method to characterize spatiotemporal propagation
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
In a recent study on wide-field calcium images in mice before and after stroke [1] singular value decomposition (SVD) was used to perform a spatiotemporal analysis of movement-evoked global cortical events. Indicators such as angle and smoothness of the propagation were defined that allowed to compare different stroke rehabilitation therapies. This method worked because the events were truly global (e.g., basically all pixels in the field of view were participating). By contrast, in a follow-up study on a mouse model of autism we now also include non-complete events but for such events SVD does not work. Thus, novel and more general approaches are needed and this need is addressed here.

Methods
Adaptive coincidence detection and the SPIKE-synchronizarion and SPIKE-order framework [2] are used to identify (global or non-global) events and to sort the participating pixels of each event from leader to follower. From the resulting two-dimensional propagation patterns, we define various indicators such as completeness (fraction of participating pixels), connectedness (clustering of these pixels) and correlation (similarity of rank order among neighboring pixels). The angel of propagation is defined from the resultant length [3] of the direction vectors of all pairs of participating pixels and its carefully renormalized amplitude is an indicator of the strength of the propagation.


Results
We illustrate the new methods using both simulated data for verification and experimental data for exploration. These are typically non-global events
recorded using wide-field calcium imaging to monitor cortical activity in a Shank3b mouse model of autism from late development through adulthood, and under isoflurane anesthesia to manipulate the brain state [4].
We here show that these new methods, and in particular the angle and the strength of the propagation, generalise and improve on the original SVD method in terms of both accuracy and speed.

Discussion
Together, the five indicators completeness, connectedness, correlation, angle and amplitude provide a full characterization of the spatiotemporal activity. Importantly, this new approach is so far the only method that allows calculating the angle and the strength of the propagation for non-complete global events.\u2028
The corresponding scientific article is currently under preparation.

References
[1] Cecchini, G., ... Kreuz, T. (2021). Cortical propagation tracks functional recovery after stroke. PLoS Comput Biol 17: e1008963. https://doi.org/10.1371/journal.pcbi.1008963 
[2] Kreuz, T., ... Mulansky, M. (2017). Leaders and followers: Quantifying consistency in spatio-temporal propagation patterns. New Journal of Physics 19, 043028. https://doi.org/10.1088/1367-2630/aa68c3
[3] Andrzejak, R. G., ... Schindler, K. (2023). High expectations on phase locking: Better quantifying the concentration of circular data. Chaos 33, 091106. https://doi.org/10.1063/5.0166468
[4] Montagni, E., ... Allegra Mascaro, A. L. (2025). Age-dependent cortical overconnectivity in shank3 mice is reversed by anesthesia. Translational Psychiatry 15 (1), 154. https://doi.org/10.1038/s41398-025-03377-5

Acknowledgement
This work has been funded by Telethon Seed Grant Spring Renewal 2025 PHEM (GSA25E002), the Italian Ministry of Universities and Research on the project THE Tuscany Health Ecosystem (ECS_00000017), MUR_ PNRR. 

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P069: EFFECT OF Ca2+ BUFFERS WITH MULTIPLE BINDING SITES ON SHORT-TERM SYNAPTIC PLASTICITY
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction


Ca2+ions are essential for triggering and modulating synaptic neurotransmitter release. Since most Ca2+
entering the cell is quickly bound by Ca2+ buffers, these molecules strongly shape the synaptic dynamics.
Two mechanisms have been proposed for buffer-driven short-term synaptic changes: (1) facilitation by
buffer saturation [1–3], and (2) facilitation by translocation of membrane-bound buffers into the synaptic
terminal [4].
Here, we systematically examine the impact of Ca2+buffers on the dynamics of Ca2+transients. We
focus on buffers with two Ca2+binding sites with distinct binding kinetics, characterizing buffers such as
calmodulin and calretinin, and we explore the effects of changes in buffer diffusivity upon Ca2+binding.

Methods
To explore the impact of Ca2+buffering properties on Ca2+transient dynamics, we numerically solve
reaction–diffusion equations describing the influx, diffusion, and mutual binding of Ca2+and buffer con-
centration fields in an enclosed volume simulating a single synaptic terminal. Vesicle pool dynamics are
not modeled, as we focus on synaptic plasticity effects arising solely from changes in local Ca2+transients
during a train of action potentials, upstream of additional plasticity effects due to vesicle pool depletion
and recovery. Equations are solved using the CalC (Calcium Calculator) software (GitHub: mvvik), with
wrapper code written in MATLAB (MathWorks, Inc.).

Results
Beyond facilitation via buffer saturation and dislocation, we find that strong depression of Ca2+transients
can occur in the presence of Ca2+-buffers with two binding sites, provided the second binding event is
much faster than the first. We refer to this effect as buffer priming, previously hypothesized in response
to calretinin overexpression [5]. We also demonstrate that certain buffering regimes produce complex
Ca2+dynamics, with facilitation followed by depression or vice versa. Finally, we systematically analyze
how these effects depend on binding properties and changes in buffer diffusivity through parameter sweeps.

Discussion
Although our results are based purely on computational modeling, it is valuable to systematically explore
how facilitation and depression of Ca2+transients depend on the kinetics, affinities, and mobilities of distinct
Ca2+-bound states of buffers with multiple binding sites. Such buffers are widely expressed in neurons,
yet their properties are difficult to measure. Buffer expression profiles differ across neuron classes, shaping
the synaptic dynamics. We believe this work helps elucidate the interplay between Ca2+homeostasis and
short-term synaptic dynamics, revealing the broader impact of complex buffer binding dynamics on cellular
Ca2+signaling.

References
[1] Klingauf, J., & Neher, E. (1997). Modeling buffered ca2+ diffusion near the membrane(...) Biophysical
Journal, 72 (2), 674–690.
[2] Blatow, M., Caputi, A., Burnashev, N., Monyer, H., & Rozov, A. (2003). Ca2+ buffer saturation
underlies paired pulse facilitation in calbindin(...) Neuron, 38 (1), 79–88.
[3] Matveev, V., Zucker, R., & Sherman, A. (2004). Facilitation through buffer saturation(...) Biophysical
journal, 86 (5), 2691–2709.
[4] Burnashev, N., & Rozov, A. (2005). Presynaptic ca2+ dynamics, ca2+ buffers(...) Cell calcium, 37 (5),
489–495.
[5] Bolshakov, A., Kolleker, A., Volkova, E., Valiullina-Rakhmatullina, F., Kolosov, P., & Rozov, A.
(2019). Overexpression of calretinin(...) Frontiers in Cellular Neuroscience, 13, 91.

Acknowledgement
I would like to sincerely thank my advisor, Victor Matveev, for his invaluable guidance, support, and mentorship throughout this work. It has, and will continue to be, a privilege to work with him.
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P070: Modeling of Cross-Frequency Brain Dynamics in Mice Cortical Region
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Large-scale brain activity shows complex dynamics that can be better interpreted through mathematical modeling. The very nature of neural activity - multi-scale, noisy, nonstationary, and highly variable across space and subjects - makes it difficult to define a model that is both computationally feasible and biologically meaningful. Here, we focus on the oscillatory components of this activity and propose a model of cross-frequency band interactions. Couplings between these bands can facilitate network communications and modulate information transfer [1]. We develop a prediction-based linear model estimating effective connectivity and characterize such couplings in cortical recordings of mice under anesthesia.


Methods
In terms of data processing, we extracted time-resolved band power using a continuous Morlet wavelet filter bank, downsampled, applied log-amplitude scaling, and performed per-band, per-channel z-score normalization.
We then modeled effective connectivity with a linear time-delayed model to track how band power evolves across channels over time. The model is estimated by minimizing a cost function combining the sum of squared residuals between predicted and observed states with an L1 penalty on the transition matrix [2], which promotes sparsity by shrinking weak connections toward zero, improving generalization and interpretability. A regularization parameter controls the trade-off between data fit and sparsity.

Results
We evaluated our model on ECoG data from a 32-electrode array evenly covering a large portion of the cortical dorsal surface (Fig.1 E) in anesthetized mice [3]. From channel-wise Morlet wavelets, we defined physiologically relevant bands (delta, theta, spindles, low gamma) and used the model to predict band-power dynamics from cross-frequency and cross-channel couplings. Preliminary results from this approach revealed key properties of cortical activity: certain frequency bands, such as delta and low gamma, show more predictive influence than others on the evolution of the cortical network (Fig.1 D). We also identified cross-channel and cross-frequency interactions, as well as the predictive influence of each band per channel (Fig.1 A-C).


Discussion
This framework captures how neural activity spreads across cortical regions and frequency bands. In this formulation, effective connectivity describes how activity in one frequency band shapes future activity in another by including past temporal information in the model formulation. By representing each frequency’s power as a separate state, the model naturally integrates these influences, allowing it to capture both cross-channel and cross-frequency interactions, as seen in Fig.1 A-B, respectively. Thus, preliminary results highlight the model’s promise for describing complex multi-scale brain dynamics.

Figure 1. A) Cross-channel interactions summed over all frequency bands. B) Cross-frequency interactions summed over all channels. C) Summed band activation per channel. D) Frequency band predictive influence in future states. E) Illustration of the mouse dorsal portion of the cortex with the 32-electrode ECoG grid.

References
1. Canolty, R. T., & Knight, R. T. (2010). The functional role of cross-frequency coupling. Trends in cognitive sciences, 14(11), 506–515. https://doi.org/10.1016/j.tics.2010.09.001
2. Tibshirani, R. (1996). Regression shrinkage and selection via the lasso. Journal of the Royal Statistical Society Series B: Statistical Methodology, 58(1), 267–288. https://doi.org/10.1111/j.2517-6161.1996.tb02080.x
3. Pedrosa, R., Nazari, M., Mohajerani, M. H., Knöpfel, T., Stella, F., & Battaglia, F. P. (2022). Hippocampal gamma and sharp wave/ripples mediate bidirectional interactions with cortical networks during sleep. Proceedings of the National Academy of Sciences, 119(44), e2204959119. https://doi.org/10.1073/pnas.2204959119


Acknowledgement
The authors thank Rafael Pedrosa for the dataset. This work is supported by the Project Dutch Brain Interface Initiative (DBI2) with Project number 024.005.022 of the Research Programme Gravitation, which is financed by the Dutch Ministry of Education, Culture and Science (OCW) via the Dutch Research Council (NWO). The authors declare no conflict of interest.
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P071: Balanced E–I gain sets spike predictability from synaptic history
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Neurons encode, compute, and transmit information through spikes, yet the functional meaning of a spike depends on how reliably it reflects the recent synaptic events that generated it. In many neural circuits, excitation and inhibition are co-active and approximately balanced, placing neurons in a conductance-driven regime where spike timing emerges from the interaction between fast excitatory–inhibitory (E–I) competition and intrinsic membrane nonlinearities such as thresholding, refractoriness, and adaptation. Here we ask how the predictability of near-future spiking from recent local E–I history depends on the magnitude and statistics of balanced synaptic drive.


Methods
We simulated a biophysical neuron receiving balanced excitatory and inhibitory synaptic inputs. Three parameters were systematically varied: (i) balanced synaptic gain, implemented by increasing excitatory and inhibitory conductance per event together in matched proportion; (ii) presynaptic input rate, shaping the temporal statistics of synaptic events; and (iii) the balance point of mean drive (balanced voltage). For each condition, we evaluated how well recent E–I history predicted imminent spikes. Predictability was quantified using two decoders: a linear generalized linear model (GLM) and a nonlinear multilayer perceptron (MLP). (Fig. 1). Model performance was evaluated using precision–recall area under the curve (PR-AUC).

Results
Predictability increased steeply with balanced E–I gain across the explored parameter space. Standardized regression analysis showed that balanced synaptic gain was the dominant determinant of PR-AUC, exerting a substantially larger effect than other parameters. Firing rate provided the second strongest contribution, whereas variations in presynaptic input frequency and balanced mean voltage produced comparatively minor effects. Increasing input frequency modestly improved predictability at low firing regimes but showed rapid saturation once firing rates plateaued. Across all parameter regimes, the MLP decoder consistently outperformed the GLM decoder.


Discussion
These findings reveal a regime-dependent predictability landscape: Strengthening excitation and inhibition together increases the reliability with which recent local synaptic competition can be decoded from spikes. In contrast, input frequency and mean voltage balance exert limited direct influence. Together, these findings indicate that synaptic gain modulation can tune neuronal computation between stochastic spiking and history-dependent gating without requiring shifts in E–I ratio or intrinsic neuronal properties.

Figure 1. Schematic overview of the spike prediction pipeline. A biophysical neuron model receives balanced excitatory and inhibitory synaptic inputs. The recent temporal history of these inputs, along with the neuron’s own past output spikes, is extracted and fed into a deep neural network (DNN) to predict imminent spikes.

Acknowledgement
Work supported in part by graduate summer funding to HL from the Program in Computational Biology and Biomedical Informatics, and by NIH R01 NS011613 to RAM. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Speakers
avatar for Robert McDougal

Robert McDougal

Associate Professor, Yale University
Looking for a postgrad or postdoc position implementing simulation methods? I'm hiring.I'm an Associate Professor in the Health Informatics division of Biostatistics, and a developer for NEURON and ModelDB. Computationally and mathematically, I'm interested in dynamical systems modeling... Read More →
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P072: Event-based machine-learned reduction of biophysically detailed neuron models
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Biophysical models impose substantial computational burdens, limiting large-scale simulation of complex neuronal dynamics, particularly with morphologically detailed neuron models. Previous evidence [1] suggests that the neuronal spiking behavior is primarily constrained by recent causal stimulus events rather than continuous full-timescale integration, which makes event-driven dynamical computation possible. We developed a machine-learning framework with a recurrent architecture for sustained spike prediction. The framework replaces computationally expensive continuous differential equation solving with an event-based mechanism, enabling temporal computation without requiring timestep-level simulation.

Methods
The framework uses recent excitatory and inhibitory events as input to recurrent neural architectures (LSTM/GRU) to encode temporal neuronal dynamics and learn a reduced representation of the latent state. Then we utilize a downstream multilayer perceptron to predict whether or not the neuron will spike, and if it does, the next-spike time (NST). Following individual spike evaluation, the trained framework was further tested under 40000 ms sustained neuronal activity driven by excitatory and inhibitory event streams at 200 Hz and 67 Hz, respectively, where predicted spikes constantly influenced subsequent neuronal activity, to estimate long-term temporal stability and dynamic spike prediction performance.


Results
Trained on a dataset of over one million stimulation trials and tested on 38k trials, the proposed event-driven framework achieved an F1 score and AUC of > 0.99, with a next-spike timing (NST) mean absolute error (MAE) of 0.07 ms, approaching the intrinsic temporal resolution of the NEURON simulation environment. Under sustained neuronal activity over a 40,000 ms simulation window, the framework reproduced 929 of 947 ground-truth spikes with only 51 missed spikes and 33 false-positive predictions, exceeding the performance of the baseline event-based model, which reproduced 135 false positives and missed 76 spikes under the same conditions.

Discussion
The stable performance observed under sustained neuronal activity suggests that the framework can preserve long-term temporal consistency beyond isolated spike prediction tasks, potentially including in network models, with potential run-time improvements for large cell models. However, the resulting errors differ from those of traditional biophysical models, so further work is needed to understand their effects on system behavior. Studying parameter sweeps or heterogeneous models would require incorporating parameters of interest into the machine learned model, re-introducing complexity. Extending the framework to generalize across broader biophysical conditions remains an important direction for future work.

References
Cudone, E., Lower, A. M., & McDougal, R. A. (2023). Reproducibility of biophysical in silico neuron states and spikes from event-based partial histories. PLOS Computational Biology, 19(10), e1011548.


Acknowledgement
Research was supported by the National Institute of Neurological Disease and Stroke of the National Institutes of Health under award number R01NS011613. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Speakers
avatar for Robert McDougal

Robert McDougal

Associate Professor, Yale University
Looking for a postgrad or postdoc position implementing simulation methods? I'm hiring.I'm an Associate Professor in the Health Informatics division of Biostatistics, and a developer for NEURON and ModelDB. Computationally and mathematically, I'm interested in dynamical systems modeling... Read More →
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P073: Evaluating parameter space stiffness of maximum entropy models and departure from criticality
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
The emergence of collective behaviour in biological systems remains to be fully understood. Models inspired by statistical physics, where neurons are treated as Ising-like variables, provide an appealing approach to fill this conceptual gap. They offer, notably, a principled framework for inferring the effective interactions and constraints that shape the collective activity, as well a method for detecting criticality without relying on avalanche calculations [1].


Methods
We focus here on Maximum Entropy Models (MEM), where a probability distribution over states is inferred by maximizing its entropy while enforcing a match between the expectation values of a given set of observables and their empirical averages. This procedure results in a Boltzmann-like distribution with temperature  and a Hamiltonian constrained by the chosen observables, parameterized by a set of Lagrange multipliers. While this approach is typically applied to experimental data, here we apply it to simulation results in order to systematically study how variations of the structural and dynamical model parameters map to changes in the effective parameters of the inferred MEM.


Results
We implement an integrate-and-fire (IF) model known to be poised at criticality [2] and train a MEM consistent with the chosen observables, namely the mean activity and pairwise correlations. The inferred Boltzmann-like distribution is parameterized by so-called local fields and effective couplings. It can be used to calculate the covariance matrix between the observables, which, in turn, is equivalent to the Fisher Information Matrix (FIM). We characterize the stiffness of the model based on the eigenvalue spectrum, and a preliminary analysis consists of imposing incremental parameter changes in the direction of the leading eigenvalue. This leads to a new model whose departure from criticality can then be evaluated.


Discussion
Future work includes the study of the covariance between structural parameters and MEM parameters, with the goal to identify how structural features of the IF model are associated with criticality. Further investigation will also evaluate whether a two-compartiment model endowed with an intrinsic bursting mechanism can be tackled with MEMs.  


References
1. Meshulam, L., & Bialek, W. (2025). Statistical mechanics for networks of real neurons. Reviews of Modern Physics, 97(4) 045002. doi:10.1103/jcrn-3nrc
2. Simões, T. S. A. N., Filho, C. I. N. S., Herrmann, H. J., Andrade, J. S., Jr, & de Arcangelis, L. (2024). Thermodynamic analog of integrate-and-fire neuronal networks by maximum entropy modelling. Scientific Reports, 14(1), 9480. doi:10.1038/s41598-024-60117-3

Acknowledgement
This work was funded by the Natural Sciences and Engineering Research Council of Canada and the New-Brunswick Innovation Foundation.

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P074: Dynamic Functional Connectivity Resolves Brain Integration-Segregation Trade-off Under Costly Links
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Dynamic functional connectivity (dFC) is a pervasive feature of brain activity, even at rest, but its functional role remains debated. We ask whether temporal reconfiguration of functional links can be advantageous when maintaining links is costly. We hypothesize that dFC helps resolve the trade-off between large-scale integration and transient local segregation by reusing a limited communication budget over time.


Methods
Resting-state fMRI dFC was modeled as a cost-constrained temporal communication network. Sliding-window functional-connectivity frames were binarized at different densities and compared with equal-cost static architectures and temporal null models. Information dispatch was quantified using smart and random walkers, measuring irrigation reach, penalized latency, temporal clustering, return latency and neighborhood retention. A connectome-based mean-field model was used as a mechanistic benchmark.


Results
Empirical dFC outperformed equal-cost static networks in sparse, high-cost regimes, allowing information to reach more nodes and reducing penalized latency. However, more randomized temporal nulls often spread information even more efficiently, showing that empirical dFC is not optimized for diffusion alone. Empirical networks also preserved strong spatial and temporal clustering, rapid return to source nodes and high neighborhood retention, supporting transient local segregation.


Discussion
These findings suggest that resting-state dFC is neither a mere by-product of neural dynamics nor a simple maximizer of global spreading. Instead, it reflects a structured regime of controlled persistence and renewal: local neighborhoods remain stable long enough for transient recirculation, before broader network-wide spreading occurs. dFC may therefore be a resource-efficient solution to competing demands for integration and segregation in brain communication.


References
Mengiste, S.A., and Battaglia, D. (2026). Dynamic Functional Connectivity Resolves Brain Integration-Segregation Trade-off Under Costly Links. arXiv. https://doi.org/10.48550/arXiv.2604.11608.

Acknowledgement
This work was supported by the PEPR Sané Numérique program (France 2030), project “Brain Health Trajectories (BHT)”, implemented by the Agence Nationale de la Recherche (ANR) under grant number ANR-22-PESN-0012-BHT. We wish to thank Alain Barrat, Caio Seguin and Sinisa Pajevic for inspiring discussions and Anagh Pathak for sharing time-series from connectome-based simulations.

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P075: Simulating bilingual naming in laterally-connected self-organizing maps
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
The BiLex model simulates the bilingual language system: two phonetic self-organizing maps (SOMs) represent English and Spanish words, linked to a shared semantic map via bidirectional associative connections (Fig.1a) [1]. Traditional SOMs use neighborhood activations; the laterally-connected BiLex uses short-range excitation and long-range inhibition, enabling mechanistic examination of within- and between-map lexical-semantic interactions. Semantic effects — familiarity, typicality, and specificity — can emerge from lateral interactions. Lateral excitation-inhibition focuses activation over settling steps, providing a novel response time measure. Naming accuracy and response time were examined in English and Spanish.


Methods
Phonetic representations used IPA-based feature encodings. Semantic representations, superordinate membership, and typicality were defined using GPT-4o [2] (>90% MTurk agreement): feature semantics and superordinate-subordinate pairs (yes/no word-feature queries e.g., "is apple a fruit?"; typicality as a 0-1 category-membership rating. SOMs were trained by word-frequency sampling (a familiarity proxy), learning boosted or penalized based on expected representation. Learned connections linked all maps, superordinates on the phonetic map via subordinates. Naming was simulated by presenting a word to the semantic map, driving lateral interactions within and between maps until activation settled; response time was settling steps to certainty.


Results
Overall accuracy was 73.6% (English) and 70.5% (Spanish), within the range for healthy bilingual adults on naming tasks [3]. Most errors were semantically related (49.1%), superordinate responses (28.0%), or phonological (9.2%); 8.6% were unrelated and 3.0% failed to converge. Typicality and word frequency were positively correlated, rs(664) = .115, p = .003. Higher frequency was correlated with faster (English rs(664) = −.261, Spanish rs = −.180) and more accurate naming (English rs(664) = .157, Spanish rs(664) = .225; all p < 0.001). See Fig. 1b, c. Excitation-inhibition dynamics enabled response time measurements via map activation settling steps. The laterally-connected BiLex model successfully simulated naming in both languages.

Discussion
A biologically plausible model should produce human-like errors rather than random failures. Error types matched those documented in the naming literature on semantic cognition and lexical access [4]: within-category coordinate errors, phonological similarity errors, or superordinate responses to subordinate category members. A positive correlation between typicality and word frequency suggested that higher-frequency words tend to be more typical category members, and atypicality in low-frequency words may contribute to naming difficulty. Structured errors validate the model and provided insight into underlying semantic and lexical mechanisms. Future work will examine lexical-semantic impairments and potential treatments.

Figure 1. Left: BiLex model with lateral connections, adapted from [1]. Naming is simulated by presenting an input to the semantic map, propagating activation through bidirectional associative connections, and producing a response from a phonetic map, in English and Spanish. Right: accuracy significantly increased with word frequency (p < 0.001) while response times were significantly faster (p < 0.001).

References
[1] Peñaloza, C., et al. (2019). BiLex: A computational approach to the effects of age of acquisition and language exposure on bilingual lexical access. Brain and Language, 195, Article 104643. https://doi.org/10.1016/j.bandl.2019.104643
[2] OpenAI. (2024). Hello GPT-4o. https://openai.com/index/hello-gpt-4o/
[3] Kohnert, K. J., Hernandez, A. E., & Bates, E. (1998). Bilingual performance on the Boston Naming Test: Preliminary norms in Spanish and English. Brain and Language, 65(3), 422–440. https://doi.org/10.1006/brln.1998.2001
[4] Rogers, T. T., et al. (2015). Disorders of representation and control in semantic cognition: Effects of familiarity, typicality, and specificity. Neuropsychologia, 76, 220–239. https://doi.org/10.1016/j.neuropsychologia.2015.04.015



Acknowledgement
This research was supported through the NIH under grant 5R01DC020653-02.

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P076: A Recurrent Circuit for Two Streams of Evidence Accumulation As a Decision-Making Model
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction

Many decisions require combining multiple evidence streams into a single action. In the human double-decision random-dot task, participants view moving colored dots and report a single choice among four spatial targets that jointly encode motion direction (left/right) and dominant color (blue/yellow) [1].  Motion and color coherences jointly determine the correct target. We show that a single LIP-inspired recurrent circuit reproduces the key error-rate (ER) and reaction-time (RT) signatures of both 2T trials (two targets; motion only) and 4T trials (four targets; motion+color), including similar ERs but longer RTs in 4T compared with 2T. We then ask how adding a second stream reshapes the decision-manifold geometry of population dynamics.



Methods
We used an E/I neural-field model of LIP with distance-dependent connectivity, extending the 2-target circuit (2T) of Monsalve-Mercado et al. [2] to four targets (4T) with four target-in (Tin) populations. Each target received a Gaussian input bump whose amplitude scaled with stimulus coherence. Tin activity bumps competed via shared broad inhibition (winner-take-all). Motion and color were independent noisy evidence streams with separate gains. Stimulus drive was maintained throughout the entire decision process. ER was the fraction of trials in which the correct Tin won. RT was defined as the first time the gap between the largest and second-largest Tin activities exceeded a fixed value. The decision manifold is reproduced via PCA.

Results

Our 4T network qualitatively captured the dependence of behavioral error rate (ER) and reaction time (RT) on motion and color coherence in the double-decision task [1]: low coherences yielded higher ERs and longer RTs, whereas high coherences produced lower ERs and shorter RTs. Motion outperformed color in the data and was captured by a higher motion-input gain. Model RTs required an additive 0.4 s offset consistent with non-decision time. Comparing matched 2T and 4T conditions, ERs were similar but RTs were consistently longer in 4T, consistent with behavioral results. Population activity showed a richer decision-manifold geometry in 4T, with participation ratio increasing nonlinearly from just above 2 in 2T to around 6 in 4T.



Discussion

A single LIP-inspired E/I neural field with local excitation and broad inhibition can account for core signatures of human double decisions [1]. In the model, four Tin activity bumps compete within a shared inhibitory pool, naturally producing a reaction-time cost in 4T without a comparable loss in accuracy, consistent with parallel evidence acquisition but a serial bottleneck in commitment. Adding a second evidence stream also reshapes state-space structure: effective dimensionality increases markedly from 2T to 4T, and low-coherence trials dwell longer near a quasi-indecision region before diverging toward the eventual choice state. This circuit provides a mechanistic bridge between multi-attribute behavior and decision-manifold geometry.


References

1 - Kang, Y. H., Löffler, A., Jeurissen, D., Zylberberg, A., Wolpert, D. M., & Shadlen, M. N. (2021). Multiple decisions about one object involve parallel sensory acquisition but time-multiplexed evidence incorporation. eLife, 10, e63721. https://doi.org/10.7554/eLife.63721
2 - Monsalve-Mercado, M. M., Stine, G. M., Shadlen, M. N., & Miller, K. D. (2025). The geometry of the neural state space of decisions. bioRxiv. https://doi.org/10.1101/2025.01.24.634806


Acknowledgement
I thank Prof. Kenneth D. Miller and his lab members for support and discussions. I was supported by the M.Sc. Neuroscience program at the Bernstein Center for Computational Neuroscience at the University of Freiburg, Germany and by an external research internship at Columbia University at the City of New York, USA.

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P077: Homophily-informed generative models of brain maps
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Whole-brain maps of structural and functional features provide complementary views of cortical organization [1]. Despite their diversity, these maps exhibit structured spatial patterns, suggesting that common organizing principles shape the topographic distribution of biological features across the cortex. To better understand the underlying forces shaping brain organization, we quantified the homophily - the propensity for brain regions proximal in physical, connectivity, or biological spaces to exhibit similar properties – of 43 brain maps [2], introduce a generative framework that preserves empirical homophilic structures, then use it to identify patterns of unexplained variation and build biologically rich null models. 

Methods
Homophily was quantified using Moran’s I [3], with respect to six inter-regional relationship matrices capturing geodesic proximity, structural and functional connectivity, as well as laminar, receptor, and genetic similarity. We then developed a generative model preserving the multimodal homophilic structure of empirical maps. Starting from random initial conditions, simulated annealing iteratively permuted regional values to minimize differences in Moran’s I across all modalities simultaneously (Fig. 1a). We generated 500 surrogate maps for each empirical map to quantify reconstruction accuracy and estimate the unique contribution of each modality. Residuals were also analyzed to identify patterns of unexplained variation.

Results
Homophily varied markedly across brain maps. Most maps were more strongly aligned with receptor and transcriptomic similarity than with geodesic proximity. Surrogate maps generated by preserving multimodal homophily accurately reproduced empirical topographies (Fig. 1b), with reconstruction accuracy strongly related to overall homophily (r=0.94). Leave-one-out analyses identified receptor similarity as the largest unique contributor, followed by gene similarity and functional connectivity. Residual analyses revealed four reproducible axes of unexplained variation, suggesting the existence of additional biological and methodological influences not captured by the modeled constraints.

Discussion
We show that homophily provides a unifying framework for understanding whole-brain topographies. Brain maps were more strongly aligned with receptor and transcriptomic similarity than with geodesic proximity, indicating that biological similarity capture aspects of cortical organization that cannot be accounted for by geometry alone. By preserving multimodal homophilic structures, our generative model accurately reconstructed empirical maps and exposed reproducible residual patterns that may reflect additional organizational principles or methodological influences. More broadly, this framework enables the creation of biologically-informed surrogate models, providing a powerful tool for hypothesis testing in neuroscience.

Figure 1. (a) The generative model relies on simulated annealing to randomly permute values while minimizing the difference in autocorrelation between empirical and simulated maps. (b) Morphospace summarizing the topographic properties of the empirical and simulated maps. (c) We identified the four main axes of variance in a matrix of regional difference between simulated and empirical values.References
[1] Hansen, J. Y., & Misic, B. (2025). Integrating and interpreting brain maps. Trends in Neurosciences, 48 (8): 594–607.
[2] Markello, R. D., Hansen, J. Y., Liu, Z.-Q., Bazinet, V., Shafiei, G., Suárez, L. E., Blostein, N., Seidlitz, J., Baillet, S., Satterthwaite, T. D., Chakravarty, M. M., Raznahan, A., & Misic, B. (2022). neuromaps: structural and functional interpretation of brain maps. Nature Methods, 19 (11): 1472–1479.
[3] Moran, P. A. P. (1950). Notes on Continuous Stochastic Phenomena. Biometrika. 37 (1): 17–23.

Acknowledgement
We thank Justine Y. Hansen, Eric. G. Ceballos, Yigu Zhou, Asa Farahani, Tahmineh Taheri and Moohebat Pourmajidian for their comments and suggestions.

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P078: Identifying Neural Markers of Chronic Pain in Children with Cerebral Palsy Using Electroencephalography and Machine Learning
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Cerebral palsy (CP) is the most common childhood motor disability, with a prevalence of 1.6 per 1000 births worldwide [1]. A common symptom of CP is chronic pain, with 76% of children experiencing pain, and 33% experiencing chronic pain [2]. Existing pain assessment tools rely on self- or proxy-reporting, limiting their utility for children with communication or cognitive impairments [3]. Electroencephalography (EEG) offers a non-invasive and objective alternative by identifying neural biomarkers associated with pain [4], [5], [6]. This study aims to develop and evaluate machine learning models for classifying pain intensity in children with CP using EEG data.


Methods
Ten children with cerebral palsy and chronic pain, along with ten age-matched healthy controls, will undergo EEG recording during a hamstring stretching protocol administered by a research physiotherapist [6]. Measurements will occur in three conditions including rest, non-painful, and painful stretching. The intensity of pain will be continuously monitored and measured by either the Visual Analog Scale (VAS) for verbal participants, or the Faces Pain Scale – Revised (FPS-R) for non-verbal participants. The EEG data will then be processed, and power spectral density will be computed across all frequency bands. A support vector machine, and two deep-learning models will be evaluated on their ability to accurately classify pain EEG signals.

Results
We hypothesize that children with CP will exhibit increased theta and alpha power in the somatosensory and frontal cortices during painful stretching, in accordance with previous literature, while controls will exhibit the opposite pattern [7]. Chronic pain may also alter ERP components such as N100 and P300, reflecting abnormal cognitive processing, with greater modulations in individuals with CP due to sensorimotor impairments [7]. For classification, SVM is expected to provide strong baseline performance, while deep learning models are anticipated to outperform SVM across accuracy, sensitivity, specificity, and F1 score by capturing more nuanced frequency-specific pain patterns.


Discussion
This research holds important clinical relevance, particularly for children with CP who have been historically underrepresented in pain assessment research due to communication challenges and the subjective nature of traditional pain assessment methods. By developing objective, EEG-based biomarkers for pain detection and intensity classification, this research will fill a critical gap in pediatric pain management. Accurate identification of pain could lead to more personalized and effective treatment strategies. Ultimately, this research may inform the development of tools that could be integrated into clinical settings to support clinicians in making faster data-driven decisions about pain interventions, thus improving quality of life.


References
  1. Rosenbaum, P., et al. (2007). Developmental Medicine and Child Neurology. Supplement, 109, 8–14.
  2. Harvey, A., et al. (2024). BMC Medicine, 22(1), 238. https://doi.org/10.1186/s12916-024-03458-0
  3. Shauna Kingsnorth, et al. (2018). https://hollandbloorview.ca/research-education/knowledge-translation-products/chronic-pain-assessment-toolbox-children
  4. Rockholt, M. M., et al. (2023). Frontiers in Neuroscience, 17, 1186418. https://doi.org/10.3389/fnins.2023.1186418
  5. Chmiel, J., et al. (2025). Journal of Clinical Medicine, 14(16), 5902. https://doi.org/10.3390/jcm14165902
  6. Sabater-Gárriz, Á., et al. (2024). Research in Developmental Disabilities, 150, 104760. https://doi.org/10.1016/j.ridd.2024.104760
  7. dos Santos Pinheiro, E. S., et al. (2016). http://hdl.handle.net/20.500.12105/20252

Acknowledgement
N/A
Speakers
AM

Ariel Motsenyat

Graduate Student, University of Toronto
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P079: Competitive dynamics in a biophysical model of rat somatosensory cortex
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
The neocortex not only has the ability to represent stimuli, but it also needs to be able to categorize them for fast and efficient processing. Research has shown discrete representation in the primary auditory cortex when presented with ambiguous stimuli [1]. We hypothesize that this mutually exclusive dynamic is possible through competitive interaction between different neuronal assemblies representing the stimuli, mediated by inhibition to opposing assemblies via Martinotti cells (MC).


Methods
This study employs an existing, experimentally-valided, large-scale biophysical model of the non barrel primary somatosensory cortex (nbS1) of juvenile rates [2,3]. This level of detail allows for a manipulation of the connectome to mimic different hypotheses for how learning could affect the connectivity between different neuronal populations. Based on a previous method, the circuit presented with “pure” patterns to identify assemblies then ambiguous patterns generated from interpolation [4]. Different modifications are done to the circuit like the removal of connections between different populations of neurons, allowing for a study into how these modifications change MC’s ability to inhibit different excitatory populations.


Results
When presented with the interpolated patterns, the unmodified and naïve circuit followed it while displaying a transitional representation. However, the modified circuit with changes to connection of MC also exhibited the same behavior. This is unexpected behavior which prompted further experiments to see how competitive dynamics can be achieved in this circuit.


Discussion
Our results suggest further experimentation and a possible revision of our hypothesis. We would like to further analyze the role of top-down projections, VIP+ neurons, and hypothetical changes to synapses due to plasticity in process of learning to categorize.


References


  1. Bathellier, B., Ushakova, L., & Rumpel, S. (2012). Discrete neocortical dynamics predict behavioral categorization of sounds. Neuron, 76(2), 435–449. https://doi.org/10.1016/j.neuron.2012.07.00
  2. Reimann, M. W., … Ramaswamy, S. (2026). Modeling and simulation of neocortical micro- and mesocircuitry (Part I, anatomy). eLife, 13, RP99688. https://doi.org/10.7554/eLife.99688
  3. Isbister, J. B., … Reimann, M. W. (2026). Modeling and simulation of neocortical micro- and mesocircuitry (Part II, Physiology and experimentation). eLife, 13, RP99693. https://doi.org/10.7554/eLife.99693
  4. Ecker, A., ..., Reimann, M. W. (2024). Cortical cell assemblies and their underlying connectivity: An in silico study. PLoS Computational Biology, 20(3), e1011891. https://doi.org/10.1371/journal.pcbi.1011891



Acknowledgement
This research project is supported by funding from the Fondation Courtois, NSERC, IVADO, the CHU Sainte-Justine Research Center,  FRQS, the Canada CIFAR AI Chairs Program, Mila, and Google. Their compute infrastructure was supported through a grant from the Canada Foundation for Innovation (John Evans Leader Fund), and a grant of computing time awarded from the Digital Research Alliance of Canada.

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P080: The Synapse-Pairing Tradeoff: How Clustering, Bursts, and Dendritic Location Enable Robust Plasticity In-Vivo
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Cortical representations are thought to arise from stable network motifs formed by neuronal assemblies, with synaptic plasticity between pyramidal cells (PCs) playing a central role in their formation, competition, and maintenance. While rules governing such synaptic changes have been well characterized in slice conditions, their implications for learning in awake behaving animals remain an active area of research. Here we use biophysically detailed simulations with calibrated ion channels, background synaptic activity, and calcium-based plasticity rules to investigate mechanisms enabling reliable plasticity in-vivo. We find that spatially clustered activation and burst firing offer robust pathways for LTP under physiological conditions.


Methods
We used biophysically detailed simulations of a large-scale in-silico cortical microcircuit of rat somatosensory cortex with a calcium-based plasticity model capturing LTP and Long-Term Depression (LTD) as a function of integrated postsynaptic calcium. We parameterized voltage-gated Na⁺, K⁺, Ca²⁺, and Bk channels throughout the dendritic tree based on experimental data. To reproduce the high-conductance state of awake cortex, we incorporated stochastic background activity using Dendritic Extra-Excitatory Synapses (DEES) at 1.1 synapses/μm. We investigated clustered plasticity in L2/3 PC and L5-TTPC basal and apical dendrites under both in-vitro and in-vivo-like extracellular calcium concentrations.


Results
Synchronous activation of ≥11 clustered synapses generates dendritic plateau potentials (≥100 ms) that induce LTP in distal basal dendrites (Fig. 1). We identify a synapse-pairing tradeoff, where dendrites effectively trade the number of co-activated synapses for pairing repetitions: 16-synapse clusters achieve one-shot learning, while 8-synapse clusters require 3+ pairings. This tradeoff exhibits spatial gradients: distal dendrites achieve LTP independent of backpropagating action potentials, while proximal clusters require spike-timing coincidence. When multiple basal clusters coactivate, summated depolarizations trigger somatic bursts; both presynaptic and postsynaptic bursts drive robust LTP with all-or-none threshold dynamics.


Discussion
These findings establish multiple plasticity mechanisms within a single neuron—spatial clustering, location-dependent learning modes, and dual burst pathways—providing testable predictions for how cortical circuits implement flexible, hierarchical learning. Distal dendrites enable unsupervised learning via cluster-based LTP independent of bAPs, while proximal regions implement supervised learning requiring spike-timing coincidence. Apical dendrites receiving top-down signals can generate bursts or couple with somatic spikes via backpropagation-activated calcium (BAC) firing, a substrate for top-down plasticity modulation. These mechanisms reveal how dendrites trade synapse number for pairing repetitions under noisy physiological conditions.


References
1. Chindemi, G., Abdellah, M., Amsalem, O., Benavides-Piccione, R., Delattre, V., Doron, M., Ecker, A., Jaquier, A. T., King, J., Kumbhar, P., Monney, C., Perin, R., Rössert, C., Tuncel, A. M., Van Geit, W., DeFelipe, J., Graupner, M., Segev, I., Markram, H., & Muller, E. B. (2022). A calcium-based plasticity model for predicting long-term potentiation and depression in the neocortex.
2. Ecker, A., Egas Santander, D., Abdellah, M., Alonso, J. B., Bolaños-Puchet, S., Chindemi, G., Gowri Mariyappan, D. P., Isbister, J. B., King, J., Kumbhar, P., Magkanaris, I., Muller, E. B., & Reimann, M. W. (2025). Assemblies, synapse clustering, and network topology interact with plasticity to explain structure-function relationships of the cortical connectome.

Acknowledgement
This research project is supported by funding from the Fondation Courtois, NSERC, IVADO, the CHU Sainte-Justine Research Center, FRQS, the Canada CIFAR AI Chairs Program, Mila, and Google. Their compute infrastructure was supported through a grant from the Canada Foundation for Innovation (John Evans Leader Fund), and a grant of computing time awarded from the Digital Research Alliance of Canada.

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P081: Estimating spiking activity of cerebellar projections to the substantia nigra dopaminergic neurons during a Pavlovian task
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Imaging using GECIs is a common technique utilized to measure neuronal activity [1]. This method, however, provides a proxy for neuronal activity and extracting the spiking activity from the observed fluorescence remains an open problem [2]. We utilize a set of differential equations to infer the underlying spike train from fluorescence recordings done in mice.


Methods
We started from the model for the calcium concentration (c) and fluorescence (p) to estimate the underlying spike trains [3]. We focused on signals averaged over many trials and ignored Brownian noise and baseline fluorescence. The model assumed linear dynamics for c that decays exponentially, but each spike increases c by a fixed fraction. The dynamics of p is a nonlinear function of c with parameters specific to the indicator used. A key parameter is the fluorescent saturation ɣ. It is possible to calculate c(t) by inverting the equations of p. To do so requires that the saturation parameter ɣ is small enough that 1- ɣp is bounded away from 0. From c, the spike train S(t) can be calculated by inverting the linear differential equation.


Results
The spike train estimation method was first optimized with ground-truth data simulated across trials and averaged. This method successfully reconstructed c and S(t) from p. We then applied the method to simultaneous recordings, using fiber photometry, of neurons of the deep cerebellar nuclei (DCN) projecting to the substantia nigra pars compacta (SNc) and dopamine neurons in the SNc, in mice performing a simple Pavlovian task [4]. The obtained spike rates were compared to signals obtained from the licking rate of the animals and a rate model of the DCN neurons, in order to estimate how the firing rates are modulated by reward value and sensory stimuli.


Discussion
GECI signals provide a proxy for neural activity, but building mechanistic models that represent these signals requires neural activity rates underlying the fluorescent signals to be properly estimated. This is especially useful when the baseline and maximum rates of neural activity in the recorded regions is known and, therefore, the changes in activity due to sensory inputs, movement and extrinsic modulatory signals can be explored using meso-scale mechanistic models. We will use these results to compare different circuit motifs that include distinct feedforward and feedback connections in order to test hypotheses for the role of cerebellum inputs to the midbrain dopamine centers.


References
1. Dana H, et al. (2019). High-performance calcium sensors for imaging activity in neuronal populations and microcompartments. Nature methods, 16(7), 649–657. doi:10.1038/s41592-019-0435-6
2. Rupprecht P, et al. (2025). Spike rate inference from mouse spinal cord calcium imaging data. bioRxiv : the preprint server for biology, 2024.07.17.603957. doi:10.1101/2024.07.17.603957
3. Deneux T, et al. (2016). Accurate spike estimation from noisy calcium signals for ultrafast three-dimensional imaging of large neuronal populations in vivo. Nature communications, 7, 12190. doi:10.1038/ncomms12190
4. Washburn S, et al. (2024). The cerebellum directly modulates the substantia nigra dopaminergic activity. Nature neuroscience, 27(3), 497–513. doi:10.1038/s41593-023-01560-9

Acknowledgement
This work was conducted at New Jersey Institute of Technology using data collected at Albert Einstein College of Medicine. Financial support was provided by NIH MH060605 (FN) and NSF IOS-2002863 (HGR).

Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P082: Balancing stability and flexibility: a meta-learning algorithm for behavioral adaptation in mice
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Learning through trial and error (reinforcement learning, RL) enables animals to adapt their behavior
in dynamic environments. Updating behavior based on reward prediction errors requires balancing stability
and flexibility: learners should avoid overreacting to noise while remaining sensitive to genuine environ-
mental changes [1]. Here, we investigated how mice adjust their learning parameters under uncertainty and
developed a meta-reinforcement learning framework to account for this adaptation [2].

Methods
We manipulated two sources of environmental uncertainty: reward probabilities, which determine out-
come stochasticity, and the frequency of contingency changes, which determines volatility [3]. We first de-
rived theoretical predictions from a standard RL model by systematically varying stochasticity and volatility
to identify reward-maximizing parameter values. We then compared these predictions with mouse behavior
in a binary operant task using intracranial self-stimulation [4], ensuring stable motivation across animals,
sessions, and thousands of trials. Behavioral data were fitted with a classical RL model and used to constrain
a meta-learning procedure.

Results
Simulations predicted that the optimal learning rate should increase with environmental volatility but
decrease with stochasticity, while the optimal decision parameter (exploitation/exploration trade-off) should
decrease with both factors. Consistent with these predictions, fitted learning rates in mice varied with both
volatility and stochasticity. In contrast, decision parameter remained stable across conditions.


To account for these results, we developed a meta-RL model in which mice estimate stochasticity from
reward prediction errors and track volatility using a simple heuristic inspired by inference models. This
model provided the best explanation of behavioral data.

Discussion
Together, these results indicate that mice dynamically adjust learning rates in response to environmental
uncertainty using computationally simple estimates of volatility and stochasticity. This framework provides
a tractable approach for investigating the neural mechanisms underlying adaptive learning

References
[1] Kenji Doya. Modulators of decision making. Nature neuroscience, 11(4):410–416, 2008.
[2] Nathaniel D Daw, Yael Niv, and Peter Dayan. Uncertainty-based competition between prefrontal and
dorsolateral striatal systems for behavioral control. Nature neuroscience, 8(12):1704–1711, 2005.
[3] P Piray and ND Daw. A model for learning based on the joint estimation of stochasticity and volatility.
Nature Communication, 1(12):6587, 2021.
[4] William A Carlezon Jr and Elena H Chartoff. Intracranial self-stimulation (icss) in rodents to study the
neurobiology of motivation. Nature protocols, 2(11):2987–2995, 2007

Acknowledgement
The authors acknowledge the support of La Fondation pour la Recherche Médicale. We also thank Jacques Gautrais (CBI, Toulouse) for his valuable advice and discussions regarding analysis codes.
Monday July 13, 2026 4:20pm - 6:20pm ADT
Ballroom B2

4:20pm ADT

P083: Biophysical model of auditory thalamocortical circuit reveals GABAB-dependent control of N1 deficits in Schizophrenia
Monday July 13, 2026 4:20pm - 6:20pm ADT
Introduction
Auditory processing deficits are a core feature of schizophrenia (SZ). The N1 component of the auditory evoked potential (AEP) is reduced in SZ. N1 refractory curves describe increasing N1 amplitudes with longer inter-stimulus intervals (ISIs), suggesting dependence on slow synaptic mechanisms, including GABAB and NMDA receptors. Using a biophysical model of macaque primary auditory cortex (A1) and thalamus [1], we examine how GABAB and NMDA modulation shape N1 dynamics. We further test whether GABAB modulation can counteract N1 amplitude reductions under NMDA hypofunction. Our goal is to reproduce in-vivo N1 deficits and identify circuit mechanisms relevant to SZ.


Methods
Simulations were performed using the NEURON simulation environment and NetPyNE multiscale modeling package [2,3]. The model includes medial geniculate nucleus (MGN), thalamic reticular nucleus (TRN), and primary auditory cortex (A1). A1 is represented as a cortical column with over 12,000 neurons and ~25 million synapses. The model captures multiscale activity, including laminar local field potentials (LFPs), current source density (CSD; second spatial derivative of LFP), and neuronal firing rates. Auditory stimuli are modeled as punctate thalamic inputs to core and matrix pathways. Simulated LFPs are used to derive CSD, and resulting patterns are compared with in-vivo macaque data for validation.


Results
Brief thalamic stimulation evoked CSD sink events in A1 granular layers that closely matched in-vivo macaque responses. The model reproduced the N1 refractory curve, with event-related CSD amplitude and multi-unit activity increasing with longer inter-stimulus intervals (ISI). This relationship was strongly governed by GABAB conductance: increasing GABAB (+25%) reduced N1 amplitude across layers, most prominently in supragranular and infragranular groups, while decreasing GABAB (-25%) enhanced N1 responses. In contrast, NMDA conductance modulation (+/-25%) produced comparatively modest effects, suggesting weaker sensitivity under current conditions.


Discussion
We investigated N1 refractory dynamics by examining inter-stimulus interval dependence of GABAB conductance in the A1 model. Increased GABAB reduced N1 amplitude across layers, suggesting a potential contributory role in auditory processing deficits observed in SZ. NMDA conductance modulation produced comparatively modest effects on N1 under current conditions. Notably, reducing GABAB-enhanced N1 responses, indicating a potential compensatory mechanism for N1 reductions associated with NMDA channel hypofunction. The model reproduces key in-vivo N1 dynamics and provides a framework for probing circuit mechanisms. Future work will extend this approach to more complex responses, including mismatch negativity, which is disrupted in SZ.


References

1. Dura-Bernal, S., et al. (2023). Data-driven multiscale model of macaque auditory thalamocortical circuits. Cell Reports, 42(11), 113378.

  • 2. Dura-Bernal, S., et al. (2019). NetPyNE, a tool for data-driven multiscale modeling of brain circuits. eLife, 8, e44494.
  • 3. Hines, M. L., & Carnevale, N. T. (2001). NEURON: A tool for neuroscientists. Neuroscientist, 7(2), 123–135.


  • Acknowledgement
    Research supported by NIH R01DC019979,  NIH R01DC012947,  NIH R01NS128924-01, NIH R01MH134118-01, NIH P50MH109429, ARL Cooperative Agreement W911NF2220143

    Speakers
    SD

    Salvador Dura-Bernal

    SUNY Downstate, USA
    EI

    Ethan Irby

    Volunteer Researcher, Nathan Kline Institute for Psychiatric Research
    I am a Data Scientist and Computational Neuroscientist interested in studying psychiatric disorders and neurodegenerative disease using a biophysical modeling approach.
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P084: Mapping excitation-inhibition balance in schizophrenia with white-matter-microstructure informed modeling
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    Providing early diagnosis and personalized treatment for psychiatric disorders like schizophrenia remains challenging, due to important interpersonal differences and still elusive neuronal mechanisms. Whole-brain network models show promising results with clinical relevance for individualized treatment recommendations in neurological disorders. However, their applicability to psychiatry is still limited as models fail to account for inter-individual differences in the correlation structure of brain dynamics among psychiatric patients.


    Methods
    What physiological mechanisms should models incorporate to better account for individual profiles of brain dynamics in schizophrenia patients and healthy controls? Our study compares various metrics of white matter structure and microstructure to inform connection weights between regions. To do so, we inferred regional parameters of whole-brain mean-field models with The Virtual Brain simulator (Pille et al, 2025 bioRxiv) to account for empirical functional connectivity from resting-state functional magnetic resonance imaging of schizophrenia patients and healthy controls (2).


    Results
    We found that using global fractional anisotropy or apparent diffusion coefficient of white matter fibers to inform the weights in neural mass models can drastically improve model performance. The data-model correlations of simulated and empirical data were significantly improved (from 0.2 to 0.7) over state-of-the-art methods. This approach allows us to uncover personalized maps of excitation-inhibition imbalance, hypothesized to take place in schizophrenia. These maps prove meaningful in that they can predict diagnosis better than model-independent neuroimaging benchmarks.


    Discussion
    Our findings highlight the importance of white matter microstructure in whole-brain modeling. The findings provide a fundamentally novel bridge between cellular-scale E/I imbalance mechanisms hypothesized in schizophrenia and large-scale brain network dynamics associated with well-established biomarkers of the disorder. Personalized white-matter microstructure informed whole-brain models could therefore be relevant as platforms to simulate disorder progression for early diagnosis and to test and optimize intervention protocols toward individualized treatment recommendations.


    References
    Pille, M., Martin, L., Richter, E., Perdikis, D., Schirner, M., & Ritter, P. (2025). Fast and easy whole-brain network model parameter estimation with automatic differentiation. bioRxiv, 2025-11.
    Vohryzek, J., Aleman-Gomez, Y., Griffa, A., Raoul, J., Cleusix, M., Baumann, P. S., ... & Hagmann, P. (2020). Structural and functional connectomes from 27 schizophrenic patients and 27 matched healthy adults [Data set]. Zenodo. https://doi.org/10.5281/zenodo.3758534

    Acknowledgement
    This project was supported by the Hertie Foundation.

    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P085: Effect of visual distortion on the perception of straight lines and reaching trajectories
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    The crystalline lens or eyeglasses induce spatial distortion of images on the retina, and the nervous system itself can introduce perceptual distortion. A previous study showed a correlation between perceptual distortion and the curvature of hand trajectories during reaching movements [1]. This suggests that perceptual distortion affects motor planning. On the other hand, adaptation to image skew changes the perception of unskewed geometrical patterns [2]. Similarly, barrel distortion, a type of lens distortion, might change the internal representation to perceive external straight lines as straight. We tested whether this distortion changes line perception and whether the internal representation affects motor planning of hand trajectories.

    Methods
    Seven participants performed an adaptation task in which an image of a grid with barrel distortion was displayed on a head-mounted display. During the task, participants were required to move their heads and gaze in multiple directions. Pre- and post-adaptation changes were evaluated using two tasks: (1) a curvature discrimination task to measure the point of subjective equality (PSE) by having participants judge the convexity (upward or downward) of lines presented in the upper or lower visual field, and (2) a reaching task measuring hand trajectory curvature during straight hand movements toward targets in either visual field. The study protocol was approved by the Institutional Review Board at Yamaguchi University.

    Results
    Compared with the pre-adaptation test, the mean PSE in the post-adaptation test shifted in a direction consistent with the hypothesis that adaptation to barrel distortion leads to the perception of more outwardly curved lines as straight, in both the upper and lower visual fields. This shift was statistically significant in the upper visual field (t(X) = −2.99, p = 0.024, Fig. 1), and below the significance level in the lower visual field (t(X) = 0.59, p = 0.58). Regarding the reaching task, the initial movement direction did not change significantly across any conditions, regardless of the movement direction (leftward or rightward) or visual field (upper or lower).

    Discussion
    The PSE shift supports the hypothesis that the internal representation of line is acquired through perceptual learning. This implies that the concept of a straight lines might also be acquired as the brain constructs a consistent representation from images that appear in various shapes depending on their retinal positions.

    No observed change in the initial hand direction in reaching movements indicates that the internal spatial representation based on visual stimuli does not directly affect motor control, implying that perceptual spatial representations differ from those used in motor planning of hand trajectories.

    Figure 1. Mean PSE curvature across participants in pre- and post-adaptation curvature discrimination tests. Error bars represent the standard deviation. Positive and negative values indicate an upward- and downward-convex curves, respectively. Gray dots represent individual participant data.

    References
    1. Wolpert, D. M., Ghahramani, Z., & Jordan, M. I. (1995). Are arm trajectories planned in kinematic or dynamic coordinates? An adaptation study. Experimental brain research, 103(3), 460-470. https://doi.org/10.1007/BF00241505
    2. Habtegiorgis, S. W., Rifai, K., Lappe, M., & Wahl, S. (2017). Adaptation to skew distortions of natural scenes and retinal specificity of its aftereffects. Frontiers in Psychology, 8, 1158. https://doi.org/10.3389/fpsyg.2017.01158

    Acknowledgement
    This work was supported by the Sasakawa Scientific Research Grant from The Japan Science Society and by AMED under Grant Number JP26wm0625418h0002.

    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P086: Examining mnemonic discrimination performance in a hippocampus model using the mnemonic similarity task
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    Mnemonic Discrimination (MD) refers to the ability to distinguish novel stimuli from similar memories [1]. It is hypothesized to involve dentate gyrus (DG) pattern separation (PS) [1], which is impaired by the hyperactivity of DG granule cells (DGGCs). DGGC hyperactivity has been found in bipolar disorder [2]; such hyperactivity may subsequently impair MD. It is unclear whether DG PS is involved in both the encoding and retrieval phases of MD, or solely during encoding [3]. This distinction is important because it may clarify how changes in DGGC activity affects MD performance.


    Methods
    To address this gap, we developed a computational model of the hippocampus capable of executing the gold standard MD task for humans, the Mnemonic Similarity Task (MST) [1]. Our model simulates the ventral visual stream and entorhinal cortex via pre-trained ResNet-derived representations. It simulates DG pattern separation via k-winner-take-all dynamics, and a continuous log-sum-exp modern Hopfield network simulates the CA3’s autoassociative behaviour. Subsequently, our model’s MD performance was compared between retrieval conditions where the DG was active vs. inactive. Finally, a mediation analysis was conducted to examine if the relationship between DG excitability and MD is mediated via DG pattern separation.


    Results
    Our preliminary findings suggest that the DG is active during both encoding and retrieval, as these models exhibited better MD performance than those with the DG only active during encoding. Additionally, the mediation analysis indicated that MD performance is significantly partially mediated by DG PS. The proportion mediated ranged from 0.42 to 0.46. Total effects were also statistically significant, with coefficients between -0.80 and -0.87, indicating that, in our model, DG hyperexcitability impairs MD performance.


    Discussion
    We present a computational model of the hippocampus capable of simulating the MST. By demonstrating that PS partially mediates the relationship between DG excitability and MD performance, we therefore present a candidate mechanistic explanation for memory impairments seen in people with BD. A potential direction for future research is to explore why PS did not fully mediate MD performance. Alternatively, future studies can fit model parameters to behavioural data at the individual level, deepening our understanding of individual differences in hippocampal functioning.


    References
    1.\tStark, S. M., Kirwan, C. B., & Stark, C. E. L. (2019). Mnemonic Similarity Task: A Tool for Assessing Hippocampal Integrity. Trends in Cognitive Sciences, 23(11), 938–951.
    2.\tBakker, A., Krauss, G. L., Albert, M. S., Speck, C. L., Jones, L. R., Stark, C. E., Yassa, M. A., Bassett, S. S., Shelton, A. L., & Gallagher, M. (2012). Reduction of hippocampal hyperactivity improves cognition in amnestic mild cognitive impairment. Neuron, 74(3), 467–474.
    3.\tBernier, B. E., Lacagnina, A. F., Ayoub, A., Shue, F., Zemelman, B. V., Krasne, F. B., & Drew, M. R. (2017). Dentate Gyrus Contributes to Retrieval as well as Encoding: Evidence from Context Fear Conditioning, Recall, and Extinction. The Journal of Neuroscience, 37(26), 6359–6371.

    Acknowledgement
     
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P087: High‑Order Interactions Predict the Dimensionality of Recurrent Hidden Dynamics Across Cognitive Tasks
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    A central challenge in neuroscience is to understand how collective computations arise from the coordinated activity of many interacting units. High order interactions (HOIs)—statistical dependencies not reducible to pairwise relations—offer a principled way to quantify such emergent structure. Yet, the mechanisms that generate HOIs and their relationship to the geometry of population dynamics remain poorly understood. Here, we study how HOIs self organize in recurrent neural networks (RNNs) trained on cognitive tasks of varying complexity, and we identify a general link between informational structure and the dimensionality of the underlying dynamical trajectories.


    Methods
    Continuous‑time RNNs were trained on four tasks spanning a range of cognitive demands: Go/NoGo, Negative Patterning, Temporal Discrimination, and Context‑dependent Decision Making. After training, networks were probed with long sequences of noise or task‑related inputs to characterize their intrinsic dynamics. HOIs were quantified using O‑information and S‑information (KSG estimator, JIDT implementation (1)) across all combinations of 3–8 hidden units. The nonlinear dimensionality of the hidden‑state trajectory was quantified using correlation dimension and complemented by PCA‑based variance analyses.


    Results
    Training induced robust HOIs across tasks, with simpler tasks producing predominantly redundant interactions and more complex tasks eliciting stronger synergistic structure. Crucially, we found a systematic negative correlation between O‑information and the dimensionality of hidden‑state trajectories: networks with more synergy explored higher‑dimensional dynamical manifolds, whereas networks dominated by redundancy collapsed onto lower‑dimensional regimes. This relationship was consistent across tasks, input conditions, and network realizations. Pruning procedures that sparsified the weight matrix did not disrupt the HOI–dimensionality link


    Discussion
    Our results reveal a mechanistic coupling between informational structure and dynamical geometry in recurrent systems: synergy emerges when the network expands its accessible dynamical repertoire, while redundancy reflects a contraction onto lower‑dimensional attractors. This suggests that O‑information can serve as a general marker of dynamical richness and computational flexibility in recurrent architectures. Because the relationship holds across tasks and network configurations, it may reflect a broader organizational principle of recurrent computation. Future work will test whether this coupling persists in multitask settings, under perturbations, and in biologically inspired architectures.


    References
    (1)\tJoseph T. Lizier, "JIDT: An information-theoretic toolkit for studying the dynamics of complex systems", Frontiers in Robotics and AI 1:11, 2014; doi:10.3389/frobt.2014.00011 (pre-print: arXiv:1408.3270)


    Acknowledgement
    This work is funded by Fondecyt grant 1241469 (ANID, Chile). AC3E is funded by Basal grant AFB240002 (ANID, Chile)

    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P088: From Pixels to Percepts: Understanding Texture Discrimination in the Mouse Visual Cortex
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    Visual textures, like blades of grass or bark on a tree, are pervasive in the natural world. These patterns, characterized by statistical regularities across spatial scales, help animals navigate the world and categorize their surroundings[1]. Textures are quite complex, yet can be readily synthesized and parameterized by computational models, hence they offer a useful entry point for studying visual processing at multiple levels: from the encoding of complex image statistics to the formation of invariant representations [2]. However, the circuit-level implementation of these computations in the brain remains poorly understood.


    Methods
    As part of the Openscope initiative, we present a new open dataset [3,4] consisting of simultaneous two-photon calcium imaging across four distinct regions of the mouse visual cortex and two imaging planes of mice engaged in a texture discrimination task. We investigate how different families of textures are processed before, during and after learning a texture discrimination task. We examine how population level representations of different classes of textures are encoded within the visual cortex.


    Results

    Results suggest that internal representations of textures emerge during learning (particularly in layer 5 across visual areas V1, LM, and AL), and mirror behavioral discriminability, with these encodings being high dimensional. Furthermore, we find that these representations can be updated, generalizing to a wide set of images as task complexity increases. Interestingly, family-specific internal representations appear to be task-dependent, as during passive viewing, neural responses are more selective to individual images than  to families.



    Discussion
    Together, these results suggest that texture category representations across visual cortical areas are not fixed, but are dynamically regulated by task engagement. This is consistent with a top-down attentional mechanism impacting the encoding of naturalistic stimuli, rather than being an innate property of the visual system. These findings highlight the importance of behavioral contexts in sculpting cortical population codes.


    References

    1.Li, A., & Zaidi, Q. (2000). Perception of three-dimensional shape from texture is based on patterns of oriented energy. Vision Research, 40(2), 217–242. https://doi.org/10.1016/S0042-6989(99)00169-8
    2.Portilla, J., & Simoncelli, E. P. (2000). A parametric texture model based on joint statistics of complex wavelet coefficients. International Journal of Computer Vision, 40(1), 49–70. https://doi.org/10.1023/A:1026553619983
    3.Ager, K., Akella, S., Bawany, A., Bennett, C., Dichter, B., Ghosh, S., . . . Williams, A. (2024). The OpenScope Databook (v1.2.0) [Software]. Zenodo. https://doi.org/10.5281/zenodo.12614664
    4.DANDI:001461 [Dataset]. DANDI Archive. https://dandiarchive.org/dandiset/001461


    Acknowledgement
    This work was funded by the US National Institutes of Health (NIH) U24NS113646. The imaging dataset was obtained as part of the OpenScope program, which is operated by the Allen Institute / Neural Dynamics. We thank the OpenScope steering committee for their support, the Allen Institute founders, Paul G. And Jody Allen, and Karel Svoboda, for their vision, encouragement, and support.
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P089: Biologically plausible Dopamine-Modulated STDP Model of Pavlovian Learning in Spiking Neural Networks
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    Dopamine-modulated STDP is a key implementation of the three-factor learning rule, in which synaptic changes depend on pre- and postsynaptic activity and a modulatory signal. Izhikevich's model introduced an eligibility trace that enables delayed dopaminergic rewards to reinforce earlier neural activity, supporting reward-based learning in recurrent spiking neural networks [1]. Previous studies showed that this framework promotes feedforward organization and spatiotemporal sequence encoding [2,3]. However, dopamine acts only as a gain factor, without altering the STDP function shape. Here, we introduce a modified rule that incorporates dopamine-dependent changes in the STDP window [4], yielding more biologically realistic learning behavior.

    Methods
    A recurrent spiking neural network of 2,000 Izhikevich neurons (1,600 excitatory, 400 inhibitory) was organized into 100 overlapping stimulus subgroups. Synaptic connectivity was random (p = 0.1). Dopamine-modulated STDP was implemented using either the original Izhikevich rule or a modified rule with separate pre–post and post–pre eligibility traces and a saturating dopamine function. During 7,000 s of training, randomly selected subgroups received stimuli at random intervals, while activation of subgroup S1 triggered delayed dopamine rewards. Learning was evaluated during a 200-s reward-free test phase using spike density function peaks and AUC-based stimulus discriminability.

    Results
    In the original Izhikevich model, reward-based learning remained robust across a broad range of dopamine concentrations, with selective responses (AUC ≥ 0.9) maintained even at unrealistically high levels. In contrast, the modified model exhibited an inverted-U dependence on dopamine concentration (Fig. 1). Learning emerged at low dopamine levels, peaked at intermediate concentrations, and deteriorated above ~2 μM, where responses to rewarded and non-rewarded stimuli became indistinguishable. A narrow intermediate range (0.8–1.2 μM) displayed bistability-like behavior, with identical dopamine levels producing either high- or low-performance states depending on network history and stochastic training dynamics.


    Discussion

    Unlike the original Izhikevich model, in which dopamine only scales synaptic plasticity, the modified STDP rule allows dopamine to reshape the plasticity window. This produced an inverted-U relationship between dopamine concentration and learning performance, restricting successful conditioning to a biologically plausible range. The model also exhibited a bistability-like regime, where identical dopamine levels yielded different learning outcomes depending on network history. High dopamine concentrations impaired learning, likely through excessive potentiation that disrupted feedforward organization. These findings provide a more biologically realistic framework for dopamine-dependent learning.

    Figure 1. Learning performance as a function of dopamine reward concentration. Mean SDF peak responses during post-training testing are shown for the original Izhikevich model (black dashed line) and the modified model (red solid line), averaged over (N = 11) simulations; error bars indicate SEM. Gray curves represent responses to non-rewarded stimuli. Green shading marks regions with AUC ≥ 0.9.

    References
    1.  Izhikevich, E. M. (2007). Solving the distal reward problem through linkage of STDP and dopamine signaling. Cerebral Cortex, 17(10), 2443–2452.
    2. Jeong, I. H. & Lee, K. J. Bursting dynamics and network structural changes towards and away from a pavlovian-conditioned neural network. PLOS Complex Systems 2, e0000035 (2025).
    3. Park, W., Kim, J., Jeong, I., & Lee, K. J. (2025). Temporal Pavlovian conditioning of a model spiking neural network for discrimination sequences of short time intervals. Journal of Computational Neuroscience, 53(1), 163–179.
    4. Zhang, J. C., Lau, P. M., & Bi, G. Q. (2009). Gain in sensitivity and loss in temporal contrast of STDP by dopaminergic modulation at hippocampal synapses. Proceedings of the National Academy of Sciences, 106(31), 13028–13033.

    Acknowledgement
    This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2024-00335928).
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P090: Modeling and Analytical Characterization of Neuronal Networks Constructed from Reservoir Computing Based Model
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    Electrophysiological studies in neuroscience probe interactions among neuronal populations across multiple scales, from single-cell activity to large network dynamics [1,2]. Here, we present a computational framework to decode signals from microelectrode array (MEA) recordings [3]. The model is based on Reservoir Computing (RC) and learns spike-rate sequences to reproduce network responses to external stimuli. A key outcome is a macroscopic connectivity map capturing effective connectivity with higher accuracy than standard statistical methods such as cross-correlation and transfer entropy. We describe the model, discuss its implications and limitations, and present applications to cultured neuronal networks under different interventions.


    Methods
    The approach relies on electrophysiological recordings from mouse cortical cultures acquired via microelectrode arrays (MEA). After preprocessing (filtering and spike detection), signals are converted into multichannel instantaneous spike-rate (ISR) sequences, from which bursting episodes are extracted. These are used to train an artificial neural network with a reservoir computing (RC) architecture to learn the synaptic transmission function underlying rate-coded activity. The network is represented macroscopically, with nodes corresponding to MEA electrodes. The RC reservoir performs nonlinear transformations with leaky memory, and outputs are obtained via LASSO-regularized linear regression [4].


    Results
    Model validation followed two complementary approaches. First, the inferred connectivity map was benchmarked against a ground-truth network generated in silico, with simulations designed to replicate MEA measurements. Second, both in silico and in vitro (real neuronal cultures) data were used in a predictive framework: the model was trained and validated on spontaneous activity, while testing was performed using responses to controlled local stimuli, including optogenetic perturbations. Model predictions under identical stimuli were then compared with the recorded responses.
    In the presentation, we will report the model’s performance and highlight selected applications along with their results.

    Discussion
    In this study, we developed a computational model that decodes spatio-temporal data from electrophysiological measurements of neuronal cultures. The model reconstructs the network structure on a macroscopic domain and predicts the response to a localized stimulus. Our primary goal was to create an advanced experimental data analysis tool for processing complex time-series. The results obtained indicate that the model not only serves as a data analyzer but can also function as a network simulator.


    References
    [1] Llinás, R. R. (1988). The intrinsic electrophysiological properties of mammalian neurons: insights into central nervous system function. Science, 242(4886), 1654-1664.
    [2] Contreras, D. (2004). Electrophysiological classes of neocortical neurons. Neural Networks, 17(5-6), 633-646.
    [3] Auslender, I., Letti, G., Heydari, Y., Zaccaria, C., & Pavesi, L. (2025). Decoding neuronal networks: A Reservoir Computing approach for predicting connectivity and functionality. Neural Networks, 184, 107058.
    [4] Tibshirani, R. (1996). Regression shrinkage and selection via the lasso. Journal of the Royal Statistical Society Series B: Statistical Methodology, 58(1), 267-288.



    Acknowledgement
    This work was financed by the European Union - NextGenerationEU - National Recovery and Resilience Plan (NRRP) - Mission 4 Component 2 Investment 1.2 - "Funding projects presented by young researchers" MSCA PNRR Young Researchers, "CIRCUS project" - MSCA20240000106 - CUP E63C25000820007.

    Speakers
    IA

    Ilya Auslender

    Assistant Professor, University of Trento
    As researcher at Università di Trento, I am working on an interdisciplinary project that combines electrophysiology, optogenetics, and machine learning to study neuronal cultures and their responses.
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P091: The Drosophila connectome reveals axo-axonic synapses on descending neurons
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    Axo-axonic synapses can veto, amplify, or synchronize spikes, yet their circuit-scale logic is unknown. Using the complete electron-microscopy connectome of the adult male Drosophila ventral nerve cord (MANC v1.2.1), we charted every axo-axonic input onto the 1,314 descending neurons that carry brain commands to the ventral nerve cord.



    Methods
    A split-Gal4 driver specific to axo-axonic neurons was identified and cross to UAS-CsChrimson construct. Giant Fibers were activated by extracellular stimuli with electrodes placed in the brain. Muscle recordings were obtained from jump and flight muscles. A mouse primary antibody against ChAT was used to confirm cholinergic cells. LIF models were used with acetylcholine synapses, GABA, and glutamate. Simulations of these neurons were made using the BRIAN2 simulator for the ventral nerve cord (VNC) with the entire MANC v1.2.1 connectome. This resulted in 23,437 valid neurons and 1,152,548 connections between them. In the fly, cholinergic receptors are excitatory, whereas glutamatergic and GABAergic receptors are inhibitory.

    Results
    Only 1% of the 861,591 possible descending–descending neuron pairs form such contacts, but when present, synaptic strength grows linearly with partner number regardless of transmitter identity. By definition, any synapse connected to a descending neuron within the cord is axo-axonic. Neurons with many partners (high-degree nodes) integrate into the network without clustering into a ‘rich-club’ of hubs. We identified an octet of ascending neurons whose axo-axonic input to the Giant Fiber descending neurons predicted modulation of the escape circuit. Immunostaining confirms their cholinergic identity, while optogenetic activation confirmed that this excitatory cohort increases Giant Fiber excitability, validating connectome-derived rules.



    Discussion
    By analyzing all 1,314 brain-originating DNs, we move beyond scattered descriptions of AACs and derive circuit-level design rules for presynaptic modulation. The quantitative principles that emerged within this work are (1) extreme sparseness showing that between 0.7 and 1.2% of possible DN-to-DN, AN-to-DN, and IN-to-DN pairs form axo-axonic synapses; (2) a tight linear relation between synaptic strength and partner multiplicity; and (3) a small-world architecture that distributes integration rather than concentrating it in a rich-club core. Together, these features constitute a wiring grammar for axo-axonic control in the adult Drosophila motor system.


    References
    Ceballos, Cesar, Juan Lopez, Ty Roachford, Daniel Sanchez, Sabrina Jara, Kelli Robbins, Casey L. Spencer, Rodney Murphey, and Rodrigo FO Pena. "The Drosophila connectome reveals axo-axonic synapses on descending neurons." iScience 29, no. 5 (2026).

    Acknowledgement
    R.P. was funded by an IBRO Collaborative Research Grants. This material is also based upon work supported by the U.S. Department of Education under Research and Development Infrastructure grant no. P116H230018. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the U.S. Department of Education.
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P092: A Proposed Etiological, Pathophysiological, and Rehabilitative Framework for Focal Task-Specific Dystonia: A Theoretical-Empirical Approach
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    Focal task-specific dystonia (FTSD) is an isolated dystonia in which abnormal contractions emerge during a particular motor activity or task while other movements remain relatively spared [1]. We propose that FTSD arises when a task-specific motor synergy (TSMS) in primary motor cortex (M1) develops excitatory synapses that outpace parvalbumin (PV)-mediated inhibitory synapses, a mechanism consistent with reduced motor cortical inhibition reported in FTSD [2,3]. This imbalance gives rise to a symptom-threshold: motor output remains normal at or below a critical task intensity, whereas the dystonic synergy is recruited once that threshold is exceeded.


    Methods
    Using a single-case clinical chronology as motivation, we built a proof-of-concept spiking neural network with leaky integrate-and-fire excitatory and inhibitory populations, conductance-based synapses, probabilistic E-to-I and I-to-E connectivity, and Poisson external drive. Input amplitude was varied as a proxy for movement intensity. We modeled two TSMS states: a functional synergy with matched excitatory and inhibitory drive and a dystonic synergy with elevated excitatory strength without proportional inhibitory strengthening. Network output was quantified as population-averaged firing rate across input amplitudes.

    Results
    Balanced networks produced regular raster activity and firing rates that scaled with input, while inhibitory-cell activity rose in parallel (Fig. 1). In alternative E/I parameter regimes, stronger input recruited sufficient inhibitory feedback to stabilize or reduce firing after an initial rise. When functional and dystonic synergies coexisted, dystonic firing remained low at weak inputs but surpassed functional-synergy firing after a discrete input threshold. Thus, E/I imbalance generated an intensity-dependent switch from controlled output to hyperexcitable, dystonic-dominant activity.

    Discussion
    These results support a TSMS account in which FTSD reflects a local M1 synergy whose excitatory circuit is selectively strengthened by repeated above-capacity practice (overreaching) while its PV-mediated inhibitory circuit fails to strengthen proportionally, rather than a solely global basal ganglia or cerebellar disorder. The threshold behavior explains why symptoms can be task- and intensity-specific. We further propose below- or at-threshold retraining (BATR), a non-invasive motor-retraining protocol conceptually related to slow-down exercise [4], in which practice is constrained to at or below the symptom-threshold to strengthen PV-mediated inhibition and restore E/I balance without further potentiating dystonic excitation.

    Figure 1. A, stimulation evokes motor action via functional excitatory/inhibitory synergy, with optional overlapping dystonic synergy. B, healthy-state raster shows regular spikes across neurons. C, firing rate increases with input strength; inset shows inhibitory activity. D, altered E/I balance produces a decreasing response. E, dystonic and functional firing diverge at a threshold across input levels.

    References
    1. Albanese, A., et al. (2025). Definition and classification of dystonia. Movement Disorders, 40(7), 1248–1259.
    2. Stahl, C. M., & Frucht, S. J. (2017). Focal task-specific dystonia: A review and update. Journal of Neurology, 264(7), 1536–1541.
    3. Ridding, M. C., et al. (1995). Changes in the balance between motor cortical excitation and inhibition in focal, task-specific dystonia. Journal of Neurology, Neurosurgery & Psychiatry, 59(5), 493–498.
    4. Yoshie, M., et al. (2015). Slow-down exercise reverses sensorimotor reorganization in focal hand dystonia: A case study of a pianist. International Journal of Neurorehabilitation, 2(2), 2376–0281.

    Acknowledgement
    The authors thank colleagues who provided helpful informal feedback on earlier versions of this work.

    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P093: Stabilizing Fractional Dynamical Networks Effectively Suppresses Epileptic Seizures
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    For 15 million patients worldwide with drug-resistant epilepsy, neurostimulation is a promising solution to counteract seizure activity [1]. However, current neurostimulation devices are unable to provide personalized or adaptive care due to their over reliance on pre-programmed responses that use fixed stimulation parameters [2]. A new framework for characterizing seizure dynamics is needed to design effective stimulation. Fractional-order dynamical networks accurately capture multi-scale neural dynamics and the spatial relationship between brain regions [3]. Here, we provide a stabilizing fractional-order dynamical framework to characterize seizure dynamics across epileptic states and effectively suppress epileptic activity.


    Methods
    Using intracranial EEG data recorded from 10 focal epilepsy patients, we explicitly model the multi-scale temporal structure (captured by fractional-order exponents) and stability properties (captured by eigenvalues of fractional-order systems) across interictal, pre-ictal, ictal, and post-ictal brain states. We apply the Kolmogorov-Smirnov 2-sample statistical test to fractional-order exponents and eigenvalues during different brain states to understand the evolution of brain dynamics across patients. We apply a novel stabilizing control framework to 35 seizure snapshots. We simulate the controlled signals and compute their difference in energy with uncontrolled epileptic data to assess effective suppression.

    Results
    Our results show that our framework can capture consistent and distinct patterns over all epileptic brain states in multi-scale and stability properties across most patients. Median fractional-order exponents decreased from interictal (0.75) to pre-ictal (0.68) and ictal (0.63) and then increased during post-ictal (0.78). Eigenvalues followed a similar trend as fractional-order exponents. We observed increased variance of eigenvalues during post-ictal. Our stabilizing control framework achieved seizure suppression in 34/35 seizures, successfully stabilizing 77% of initially unstable seizures and reducing seizure amplitude by approximately 49% across all electrodes.

    Discussion
    The decrease in fractional-order exponent values during interictal to ictal indicates a progressive strengthening of long-range temporal memory as the seizure approaches, which is consistent with critical slowing [4]. Furthermore, the wide spread in fractional-order exponents during post-ictal likely suggests variable long range temporal memory properties post-seizure, without returning to baseline interictal levels. Tracking fractional-order exponents may be useful for seizure prediction in future studies. In this work, we demonstrate the capability of our state-of-the-art stabilizing state feedback control scheme to effectively suppress epileptic activity in a computationally tractable control manner that is straightforward to implement.

    Figure 1. Percentage amplitude reduction for each seizure. Gray bars represent seizures that are already stable (maximum eigenvalues < 1), while blue bars indicate seizures that require stabilization. Vertical dashed lines separate patients. Only 1 seizure increased in amplitude after control. Control reduced amplitude by an average of 48.96% + 16.94%.

    References
    [1] Edwards, C. A., Kouzani, A., Lee, K. H. & Ross, E. K. Neurostimulation devices for the treatment of neurologic disorders. In Mayo Clinic Proceedings, vol. 92, 1427–1444 (Elsevier, 2017).

    [2] Morrell, M. J. Responsive cortical stimulation for the treatment of medically intractable partial epilepsy. Neurology 77, 1295–1304 (2011).

    [3] Reed, E., Chatterjee, S., Ramos, G., Bogdan, P. & Pequito, S. Fractional cyber-neural systems—a brief survey. Annual Reviews in Control 54, 386–408 (2022).
    [4] Maturana, M. I. et al. Critical slowing down as a biomarker for seizure susceptibility. Nature communications 11, 2172 (2020).

    Acknowledgement
    EP gratefully acknowledges the support of Texas Tech University. GR is funded by national funds through FCT – Fundação para a Ciência e a Tecnologia, I.P., and, when eligible, co-funded by EU funds under project/support UID/50008/2025 – Instituto de Telecomunicações, with DOI identifier https://doi.org/10.54499/UID/50008/2025.
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P094: Neuron–Astrocyte Coupling Regulates Ion Homeostasis and Neuronal Excitability in a Multi-Compartment Model
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    Neuronal excitability depends on transmembrane gradients of sodium (Na), potassium (K), and chloride (Cl). Astrocytes contribute to ionic homeostasis by regulating extracellular ion concentrations through membrane channels, transporters, and spatial buffering across their extended processes and syncytial networks [1]. Among the main pathways are K uptake via astrocytic Na/K-ATPase (aNKA) and Kir4.1 channels, and Cl regulation via ClC-2 channels and GABA-A receptors [2, 3]. Although these mechanisms have been studied individually, their combined influence on extracellular ion dynamics and neuronal activity in the coupled neuron–extracellular space (ECS)–astrocyte system remains unclear.

    Methods
    We developed a multi-compartment model consisting of a neuron (N) interacting with an astrocytic shell (A) through a local extracellular space (E). Astrocytes are coupled via gap junctions to a distal glial syncytium (G), which exchanges ions with a bath reservoir (B). Neuronal dynamics follow Hodgkin–Huxley kinetics with voltage-gated and leak Na, K and Cl channels, muscarinic currents, neuron Na/K-ATPase (nNKA), and K–Cl cotransporters (KCC), while the ECS tracks ionic accumulation. Astrocytes include aNKA, Kir4.1 channels, Cl fluxes, and glutamate (GLT-1) and GABA (GAT) transporters. Simulations quantify how neuronal activity alters extracellular ion concentrations and how astrocytic regulation feeds back onto neuronal excitability.


    Results
    Coupling the neuron compartment to a closed extracellular space reveals strong activity-dependent ionic accumulation. During sustained stimulation, extracellular K progressively increases, shifting reversal potentials and altering neuronal firing dynamics until the system enters depolarization block. In the neuron–ECS configuration this depolarized state is stable, preventing recovery of the initial resting equilibrium. Introducing astrocytic mechanisms delay depolarization block through the interplay between K uptake and Cl fluxes. When distal buffering pathways are included, ionic redistribution through astrocytic networks and extracellular diffusion toward a bath reservoir restores the hyperpolarized resting state.

    Discussion
    These results highlight the importance of astrocyte-mediated ion regulation for stabilizing neuronal excitability. While neuronal mechanisms alone cannot recover from activity-induced ionic imbalance, astrocytic buffering reduces extracellular K accumulation and delays depolarization block. Recovery of the resting equilibrium requires distal ion redistribution through gap-junction–coupled astrocytic networks and extracellular diffusion toward distal reservoirs [4]. The efficiency of this process depends on the rate of intercellular exchange and parenchyma tortuosity, which constrains ionic diffusion. Together, these mechanisms provide a dynamical framework for how astrocytes regulate ionostasis and maintain stable neuronal activity.

    References

    1. Verkhratsky, A., & Nedergaard, M. (2018). Physiology of astroglia. Physiological reviews, 98(1), 239-389. https://doi.org/10.1152/physrev.00042.2016
    2. Kofuji, P., & Newman, E. (2004). Potassium buffering in the central nervous system. Neuroscience, 129(4), 1043-1054. https://doi.org/10.1016/j.neuroscience.2004.06.008
    3. Untiet, V., & Verkhratsky, A. (2024). How astrocytic chloride modulates brain states. BioEssays, 46(6), 2400004. https://doi.org/10.1002/bies.202400004
    4. Hübel, N., & Dahlem, M. A. (2014). Dynamics from seconds to hours in Hodgkin-Huxley model with time-dependent ion concentrations and buffer reservoirs. PLoS computational biology, 10(12), e1003941. https://doi.org/10.1371/journal.pcbi.1003941

    Acknowledgement
    We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC) [Grant ID: RGPIN 2024 04333]
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    4:20pm ADT

    P095: Universal rules for growing artificial astrocytes at electron microscopy resolution
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Introduction
    Astrocytes are ubiquitous glial cells of the cortex which display a complex ramified anatomy. Astrocyte processes envelop synapses and dendrites, mediating diverse neuromodulatory pathways. While it is speculated that the domain of astrocyte-mediated neuromodulation is influenced by their anatomy, it is currently unknown what the stereotypical shape of an astrocyte is, beyond the simple observation of their branching. Nor do we know whether astrocyte anatomy abides by universal rules across brain regions and species.

    Methods
    Employing machine learning, graph theory, and topological analysis, we developed a comprehensive library of morphometric measures that extract quantitative anatomical features of astrocytes and neurons resolved under electron microscopy (Schubert et al., 2022). Based on trends in anatomical features specific to astrocyte morphology, we developed a generative algorithm that synthesizes astrocyte branching structure, inspired by the Minimum Spanning Tree (Cuntz et al., 2011).

    Results
    Using our library of morphometric features, we can quantitatively differentiate astrocytes both from neurons and from astrocytes of different species. Astrocytes are spatially complex cells with branches packed into a small space. They have large primary branches that define the shape of their territory and fine, diffusive branchlets that fill up the space within their territory. Based on these observations, we created a generative algorithm that replicates astrocyte branched anatomy, including the distinction between primary and terminal processes across different regions and animals.

    Discussion
    We present the first systematic characterization of cortical astrocyte anatomy from high-resolution EM datasets in different species. Our analysis, in particular, allowed us to identify salient astrocyte features that, in turn, can be used to constrain the minimal spanning tree as a general recipe to grow astrocytes in silico.

    References
    Cuntz, H., Forstner, F., Borst, A., & Häusser, M. (2010). One rule to grow them all: a general theory of neuronal branching and its practical application. PLoS computational biology, 6(8), e1000877.

    Schubert, P. J., Dorkenwald, S., Januszewski, M., Klimesch, J., Svara, F., Mancu, A., ... & Kornfeld, J. (2022). SyConn2: dense synaptic connectivity inference for volume electron microscopy. Nature Methods, 19(11), 1367-1370.

    The MICrONS Consortium (2025). Functional connectomics spanning multiple areas of mouse visual cortex. Nature, 640(8058), 435–447.

    Acknowledgement
    We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC) [Grant ID: RGPIN 2024 04333, 589115 2024]
    Monday July 13, 2026 4:20pm - 6:20pm ADT
    Ballroom B2

    7:45pm ADT

    Banquet Dinner
    Monday July 13, 2026 7:45pm - 9:45pm ADT

    Monday July 13, 2026 7:45pm - 9:45pm ADT
    TBA
     
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