Consciousness depends on integration between parietal cortex
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Millions of people are administered general anesthesia each year, but it's not always easy to tell whether they are actually unconscious. A small proportion of those patients regain some awareness during medical procedures, but a new study of the brain activity that represents consciousness could prevent that potential trauma. It may also help both people in comas and scientists struggling to define which parts of the brain can claim to be key to the conscious mind.

The neural substrates of consciousness remain elusive. Competing theories that attempt to explain consciousness disagree on the contribution of frontal versus posterior cortex and omit subcortical influences. This study was aimed to test substrates and measures of consciousness, doctors recorded simultaneously from frontal cortex, parietal cortex, and subcortical structures, the striatum and thalamus, in awake, sleeping, and anesthetized macaques. They manipulated consciousness on a finer scale using thalamic stimulation, rousing macaques from continuously administered anesthesia.

The results show that, unlike measures targeting complexity, a measure additionally capturing neural integration robustly correlated with changes in consciousness. Machine learning approaches show parietal cortex, striatum, and thalamus contributed more than the frontal cortex to decoding differences in consciousness.

These findings highlight the importance of integration between parietal and subcortical structures and challenge a key role for the frontal cortex in consciousness.

Cell Systems