Looking for hidden signs of consciousness

In the 22 March issue of Nature, Kerri Smith discusses the debate over a 'brain-activity' test for patients in a vegetative state (PDF download HERE).

A team, led by Adrian Owen of the MRC Cognition and Brain Sciences Unit in Cambridge, UK, used functional magnetic resonance imaging (fMRI) to show that a woman left in a vegetative state after a car accident could respond to requests to imagine playing tennis or navigate around her house (A. Owen et al. Science 313, 1402; 2006)... Laureys, a member of this team, has now tested this technique on 24 healthy volunteers, who were similarly instructed to imagine either walking around their house or playing tennis. The tasks activate separate networks in the brain, and the scans proved able to tell correctly which task was being performed (M. Boly et al. NeuroImage doi:10.1016/j.neuroimage.2007.02.047; 2007)...showing that the method works reliably in healthy brains proves its robustness. "Our challenge is to find markers that tell us 'this is a hopeless case' or 'this is a case where we should increase our therapeutic efforts'," says Laureys.

Imagining spatial navigation (left) and playing tennis.