Friday, 15 September 2006

Finding consciousness within

It’s difficult to imagine anything worse than lying paralysed, being fully aware and yet unable to signal to your loved ones sitting around you that – yes, you can hear them, you are there. If only the doctors could scan your brain and see that you were listening and thinking. Remarkably, that’s what British researchers Adrian Owen and colleagues at the MRC Cognition and Brain Sciences Unit claim to have done.

Owen’s team scanned the brain of a 23-year-old woman left in a coma by a car accident. She had emerged from coma into what’s known as a persistent vegetative state, characterised by periods of sleep and wakefulness but showing no outward signs of being consciously aware.

First they found the language parts of her brain responded to spoken sentences, and that ambiguous sounding words like creak/creek triggered activity in an area known to be involved in selecting between alternative meanings. More amazing, however, was what happened when they asked her to imagine either playing tennis or walking around her home. The tennis instruction prompted activity in the motor control parts of her brain, whereas the home instruction triggered memory-related activity associated with navigation – both in a way indistinguishable from the activity observed when healthy participants followed the same instructions.

“Her decision to cooperate by imagining particular tasks when asked to do so represents a clear act of intention, which confirmed beyond any doubt that she was consciously aware of herself and her surroundings”, the researchers concluded.

However, commentators have advised caution in interpreting the results. “We should not generalise from this single patient, who suffered relatively few cerebral lesions, to most other vegetative state patients, who typically have massive structural brain lesions” said Lionel Naccache at the Cognitive Neuroimaging Unit, INSERM, writing in the same journal issue. “If this patient is actually conscious, why wouldn’t she be able to engage in intentional overt motor acts, given that she had not suffered functional or structural lesion of the motor pathways”, he asked.

Owen, A.M., Coleman, M.R., Boly, M., Davis, M.H., Laureys, S., & Pickard, J.D. (2006). Detecting awareness in the vegetative state. Science, 313, 1402.

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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