Central thalamus modulates consciousness by controlling layer-specific cortical interactions

Summary

Consciousness requires the capacity to experience the environment and internal states. Recordings from macaques show that during unconsciousness, spiking activity is selectively reduced in deep cortical layers and thalamus, along with diminished interactions at alpha and gamma frequencies. Gamma-frequency stimulation of the central lateral thalamus in anesthetized macaques counteracted these changes and restored consciousness. The findings suggest that the neural correlates of consciousness involve coordinated activity across corticocortical feedforward and feedback pathways, intracolumnar loops, and thalamocortical circuits.

Study at a glance

Abstract

Consciousness is the capacity to experience one’s environment and internal states. The minimal mechanisms sufficient to produce this experience, the neural correlates of consciousness (NCC), are thought to involve thalamocortical and intracortical interactions, but the key operations and circuit paths are unclear. We simultaneously recorded neural activity in central thalamus and across layers of fronto-parietal cortex in awake, sleeping and anesthetized macaques. Spiking activity was selectively reduced in deep cortical layers and thalamus during unconsciousness, as were intracolumnar and interareal interactions at alpha and gamma frequencies. Gamma-frequency stimulation, when focused on the central lateral thalamus of anesthetized macaques, counteracted these neural changes and restored consciousness. These findings suggest that the NCC involve both corticocortical feedforward and feedback pathways coordinated with intracolumnar and thalamocortical loops.