Thalamic modulation of cortical linearity across arousal states

The human brain must support both stable and flexible neural dynamics to adapt to changing contexts. The thalamus has been hypothesized to coordinate these opposing dynamical regimes in the cerebral cortex; however, this has not been directly tested at the systems level. Here, we apply a time-resolved measure of linearity to multimodal recordings in humans and macaques, demonstrating irregular fluctuations in both human functional magnetic resonance imaging and electrophysiological in the awake state. These fluctuations follow a key neuroanatomical axis of the thalamus, are diminished under pharmacological ablation of arousal, and recovered following arousal-inducing direct electrical stimulation of thalamus. Together, these findings identify a thalamic organizational axis that modulates cortical linearity across arousal states, linking thalamocortical architecture to the regulation of large-scale cortical dynamics.