CNS*2026 Halifax

Duan Li*, Anthony G. Hudetz

Center for Consciousness Science, Department of Anesthesiology, University of Michigan, Ann Arbor, MI

*Email: [email protected]

Introduction
General anesthetics profoundly reshape neuronal activity and functional interactions, yet how they alter the spatiotemporal organization of the cortex is incompletely understood. Traveling waves provide a framework for examining coordinated neural activity across the cortex, but their modulation by anesthesia remains underexplored. Recently we showed that cortical dynamics under anesthesia exhibit spontaneous transitions among discrete states, including a paradoxical state characterized by low delta power and high complexity in deep anesthesia[1]. To investigate how traveling waves vary across cortical states, we recorded hemispheric ECoG at multiple anesthetic depths and analyzed wave dynamics as a function of cortical state and frequency.

Methods
ECoG was recorded from the right hemisphere with chronically implanted 32-site flexible polymer arrays (4×8 grid) at four desflurane concentrations (6-0%) for 1 h each. Cortical states were identified using PCA of power spectrograms followed by density-based clustering across concentrations. Within each state, traveling wave episodes were detected based on stabile spatial phase gradient patterns [2] between consecutive time points [3] in the delta, theta, and gamma bands. Wave occurrence and pattern richness were quantified, the latter defined as the entropy of SVD eigenvalues of the episode similarity matrix. Plane waves were identified and further classified as feedforward (posterior-to-anterior) or feedback (anterior-to-posterior).

Results
Seven states were identified. S1-S5 broadly tracked anesthetic depth but were not tied to a specific level. S6 corresponded to burst suppression, and S7 indicated a paradoxical state mostly during deep anesthesia. In S1, theta waves were mainly feedback-directed, whereas gamma were feedforward-directed. As anesthesia deepened, delta waves became more frequent but showed reduced pattern diversity. In contrast, the occurrence and diversity of theta and gamma patterns were largely preserved. Although gamma feedforward dominance persisted, theta feedback dominance was suppressed during deep anesthesia. In S7, reductions in delta complexity and theta organization were only partially reversed, despite reduced delta power and wake-like complexity.

Discussion
General anesthesia differentially modulates cortical traveling waves across frequency bands. Loss of theta feedback dominance paired with preserved gamma feedforward propagation suggests disrupted top-down integration despite maintained bottom-up information flow. Reduced diversity of delta waves during deep anesthesia suggests a shift toward more stereotyped, low-information dynamics. Importantly, traveling waves do not fully recover in the paradoxical state suggesting that spectrally activated deep anesthetic states lack coordinated spatiotemporal organization necessary for conscious processing. These findings suggest that traveling wave dynamics provide complementary insight into brain state dynamics beyond spectral power or complexity.

References
1. Li, D., & Hudetz, A. G. (2025). Dynamic electrocortical states and paradoxical complexity during desflurane anesthesia. bioRxiv. https://doi.org/10.1101/2025.10.13.682019
2. Muller, L., Piantoni, G., Koller, D., Cash, S. S., Halgren, E., & Sejnowski, T. J. (2016). Rotating waves during human sleep spindles organize global patterns of activity that repeat precisely through the night. eLife, 5, e17267. https://doi.org/10.7554/eLife.17267
3. Das, A., Zabeh, E., Ermentrout, B., & Jacobs, J. (2024). Planar, spiral, and concentric traveling waves distinguish cognitive states in human memory. bioRxiv. https://doi.org/10.1101/2024.01.26.577456

Acknowledgments
Research was supported by the National Institute of General Medical Sciences of the National Institutes of Health under award number R01-GM056398 and the Center for Consciousness Science, Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan, USA. The authors express their gratitude to Dr. Shiyong Wang for his assistance in performing the experiments.