Brain patterns of consciousness

A study that is the product of a collaboration across seven countries has identified brain signatures that can indicate consciousness without relying on self-report or the need to ask patients to engage in a particular task. It demonstrates that conscious and unconscious patients can be differentiated after brain injury. The brain activity patterns of injury patients that are unconscious are similar to those observed in normal subjects under deep anaesthesia.

A clip from a summary of the work:

We found two main patterns of communication across regions. One simply reflected physical connections of the brain, such as communication only between pairs of regions that have a direct physical link between them. This was seen in patients with virtually no conscious experience.

One represented very complex brain-wide dynamic interactions across a set of 42 brain regions that belong to six brain networks with important roles in cognition (see image above). This complex pattern was almost only present in people with some level of consciousness.

Importantly, this complex pattern disappeared when patients were under deep anaesthesia, confirming that our methods were indeed sensitive to the patients' level of consciousness and not their general brain damage or external responsiveness.

Here is the main article's abstract:

Adopting the framework of brain dynamics as a cornerstone of human consciousness, we determined whether dynamic signal coordination provides specific and generalizable patterns pertaining to conscious and unconscious states after brain damage. A dynamic pattern of coordinated and anticoordinated functional magnetic resonance imaging signals characterized healthy individuals and minimally conscious patients. The brains of unresponsive patients showed primarily a pattern of low interareal phase coherence mainly mediated by structural connectivity, and had smaller chances to transition between patterns. The complex pattern was further corroborated in patients with covert cognition, who could perform neuroimaging mental imagery tasks, validating this pattern’s implication in consciousness. Anesthesia increased the probability of the less complex pattern to equal levels, validating its implication in unconsciousness. Our results establish that consciousness rests on the brain’s ability to sustain rich brain dynamics and pave the way for determining specific and generalizable fingerprints of conscious and unconscious states.

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