At first glance, a patient in a persistent vegetative state may appear only to be resting, eyes open. But such patients show no sign of recognizing or interacting with their surroundings, and the likelihood that they ever will decreases as the months pass. Relatives and doctors face the difficult choice between continuing or ending life support, guided only by statistics and each patient's unique clinical profile. That may soon change. Scientists at the University of Cambridge and the University of Liège in Belgium reported that they had used MRI brain-imaging technology to detect signs of awareness in a 23-year-old woman who had been in a vegetative state for five months. “The brain scan showed us that not only was she able to understand speech, she was able to follow simple instructions,” says Adrian M. Owen, lead author of the study.

The researchers first observed that ordinary speech produced responses identical to those of healthy volunteers. Because such activity could be automatic, they then asked the woman to imagine herself at Wimbledon, playing tennis. During this exercise, neurons fired in her supplementary motor area. A request for her to imagine walking through her home activated brain areas responsible for spatial navigation. Owen claims this response proves she was willfully following instructions.

Not everyone agrees. His results provoked a storm of media interest, along with skepticism from some experts. Even Owen is cautious about extending the conclusions of this study to other patients. “They're all different, including their chances of recovery,” he says. But he speculates that by using brain imaging, doctors may be able to carry on two-way “conversations” with some vegetative patients, perhaps getting them to answer simple yes-or-no questions by imagining themselves playing tennis versus navigating their home.