Friday, May 20, 2011

Alive or dead? And the brain, of course

A person is either alive, or dead, or... in a "middling state," which can be hard to decipher. According to Amber Dance's article for Nature, "Even when a team of doctors agree to diagnose a vegetative state, they have been shown to be wrong more than 40% of the time compared to the a standardized test, the Coma Recovery Scale."

In other words, when the going gets tough, we're not very good at determining whether someone is with us or not.

However, a new test, developed by Melanie Boly and her team at the University of Li├Ęge in Belgium, uses an electroencephalogram (EEG), to peer in at the brain, and the results suggest "that 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."

Here's more:
Boly and her colleagues...used EEG to measure electrical signals from the brains of 8 people in vegetative states, 13 in minimally conscious states and 22 healthy participants. The subjects were played a series of tones, which occasionally changed in pitch. The differing tone constituted a surprising event in the environment — something that the frontal cortex has to consider, so in all subjects the temporal cortex would send the frontal cortex a message.

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.

Interesting stuff. To read even more, see Test measures spark of consciousness

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