Abstract

The human brain must support both stable and flexible neural dynamics in order to adapt to changing contexts. This paper investigates the role of the thalamus, a crucial subcortical structure, in orchestrating these opposing dynamics in the cerebral cortex. Through two distinct classes of cortical projections, the thalamus is able to support distinct dynamics modes: some cells relay precise information between cortical regions, whereas others diffusely modulate ongoing cortical dynamics. Traditional approaches to analysing neural data struggle to capture the moment-to-moment intricacies of brain dynamics, akin to mapping a rivers topography without understanding its flow, or laminarity. Inspired by the field of fluid dynamics, we show that spontaneous fMRI data exhibits non-trivial fluctuations in laminarity. Propofol-induced anesthesia selectively disrupts the non-laminar aspects of cortical dynamics while preserving laminar flow, which we validate with a large-scale biophysical model of the thalamocortical system. Finally, we confirmed theoretical predictions from the biophysical model using multielectrode electrophysiological recordings from the cerebral cortex of an anesthetized macaque – direct stimulation of the diffusely-projecting thalamus restored non-laminar cortical fluctuations and the waking state. We conclude that the thalamus provides versatile control over the cortical laminar and non-laminar flows that characterize conscious states.