Scientists Develop New Tool to Distinguish Between States of Consciousness

Different brain responses linked to states of consciousness have been identified by researchers in Belgium.

They have discovered a test that can distinguish between states of consciousness using a simple electroencephalogram (EEG) and some mathematics.

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According to the researchers, the key difference between minimally conscious and totally unconscious non-coma states is communication between the frontal cortex- the planning, thinking part of the brain - and the temporal cortex, where sounds and words are processed, reports Nature.

This technique could help doctors to make accurate diagnoses about consciousness, and better predict how a patient will recover.

The Coma Recovery Scale is the current 'gold standard', said co-author Melanie Boly, a neuroscientist at the University of Liege in Belgium.

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The scale scores patients on the basis of whether they are capable of conscious behaviours such as speech and directed gaze.

Boly and her colleagues sought a biological tool to complement the behavioural scale. They used EEG to measure electrical signals from the brains of 8 people in vegetative states, 13 in minimally conscious states and 22 healthy participants.

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In minimally conscious and healthy people the frontal cortex would then send a message back to the temporal cortex. The reason for this is uncertain; it may be to let the temporal cortex know what to expect in the future. But for people in a vegetative state, the communication was one-way: signals passed from the temporal to frontal area, but not back.

EEG data are measured through the scalp, so the technique provides at best a fuzzy approximation of what is going on inside the skull.

Garrido and her colleagues took their analysis a step further. They used dynamic causal modelling, a mathematical method developed by several members of the team, to create a computer model showing the best guess of what inner-brain activity could have yielded the EEG.

The researchers have spent several years validating the technique, but it is only a model. A more direct experiment would be to use electrodes implanted in the brain, perhaps in animal studies, Boly suggested.

The study has been published in Science.

Source-ANI