Simultaneous recordings from frontal, parietal, striatal, and thalamic regions in macaques during wakefulness, sleep, and anesthesia, along with deep-brain thalamic stimulation, show that parietal cortex, striatum, and thalamus contribute more to the level of consciousness than frontal cortex. This supports Integrated Information Theory over Global Neuronal Workspace Theory and Higher-order Theories, but Integrated Information Theory does not account for subcortical structures like the striatum. The authors propose that thalamo-striatal circuits have a cause-effect structure that generates integrated information.
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.