Understanding the neural basis of consciousness requires mechanistic accounts that span multiple scales of brain organisation. Yet most existing theoretical frameworks operate at the macroscale, offering systems-level predictions without prescribing the cellular and circuit-level mechanisms that implement them. Here I argue that the multiscale architecture of the thalamocortical system offers a principled solution to this problem. Drawing on theoretical and computational work from our group, I show how the core/matrix organisation of the thalamus, in combination with the nonlinear dendritic integration properties of L5B pyramidal neurons, generates the conditions necessary for both the global state of consciousness and the specific contents of experience. A biophysical microcircuit model, extended to a corticothalamic neural mass framework, reproduces key empirical phenomena across multiple perturbation regimes - including anaesthesia, optogenetic manipulation, and pharmacological intervention - and makes predictions at the macroscale that are consistent with leading theoretical accounts.
