Patients in a vegetative state are unable to respond to stimulation with overt behavior. But recently, researchers have shown that some of them respond to simple commands by altering their brain activity while in an MRI scanner.
At the annual meeting of the Organization for Human Brain Mapping this month, they described how they have taken an important step toward helping such patients communicate.
Teams led by Adrian Owen at the Medical Research Council's Cognition and Brain Sciences Unit in Cambridge, and Steven Laureys of the Coma Science Group at the University of Liège, have scanned 23 vegetative patients. Four were able to respond to yes-no questions correctly and consistently by following instructions to imagine playing tennis when they wanted to give one response, or walking around the house when they wanted to give the other.
Those studies have led Owen to conclude that a significant minority of vegetative patients may be more aware than they seem. Since they are responsive, they are not even technically vegetative, though current diagnostic techniques - which require that they respond physically to instructions, for example by blinking - are not sensitive enough to detect that.
If they are responsive, they are capable of communicating. But how? Damian Cruse of the Cambridge group used electroencephalography (EEG), a cheaper and more portable way of measuring brain activity via electrodes pasted to the scalp.
Cruse and his colleagues asked six healthy volunteers to imagine either squeezing their right hand or wiggling the toes of both feet when presented with a tone. The imagined hand-squeezing produced a response on the left-hand side of the brain, while the toe-wiggling produced one over the center of the head.
They then applied the same procedure to a patient with "locked-in" syndrome - conscious but almost entirely paralyzed - who retains some control of his eye movements. His brain responses were the same as those in the healthy controls. Finally, they gave the instructions to a patient who had been diagnosed as being vegetative two years earlier. They found that, from the EEG signals, they could deduce which movement the patient had been instructed to imagine every time.
This result, though preliminary, suggests it might be possible to establish some sort of dialogue with some people who had previously been considered all but brain-dead.