Neurons in the thalamus and deep cortical layers are most sensitive to changes in consciousness level, consistent across different anesthetic agents and sleep. Deep layer activity is sustained by interactions with the central lateral thalamus. Consciousness also depends on deep layer neurons providing feedback to superficial layers, suggesting long-range feedback and intracolumnar signaling are important. Stimulating the central lateral thalamus in anesthetized macaques effectively restored arousal and wake-like neural processing in a location- and frequency-specific manner. These findings suggest layer-specific thalamocortical correlates of consciousness and inform how targeted deep brain stimulation can alleviate disorders of consciousness.
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.