Monday, January 01, 2007

Raising Consciousness

Continued from page 2

By Emily Singer

In 2005, Adrian Owen, a neuroscientist at the Medical Research Council in Cambridge, England, began a series of experiments to address these questions. Owen and his coworkers created a brain-imaging test they hoped would indicate whether someone was actually aware of his or her environment. An MCS patient was instructed to imagine playing tennis when she heard the word "tennis," or to imagine walking through her house when she heard the word "house"; she was then positioned in the scanner and given auditory prompts. The test was designed to evaluate both short-term memory, because the instructions were given well before the prompts, and the capacity for sustained attention, because the patient was told to continue imagining a scene until asked to stop. Most important, it was designed to require intentional action.

If you're healthy, imagining that you're playing tennis or navigating your house activates specific parts of your brain--respectively, the supplementary motor areas, which control motor responses, and the parahippocampal gyrus, which plays a role in memory of scenes. So the scientists knew exactly what to look for in patients with impaired consciousness. Their subject was a 23-year-old woman who'd been left in a vegetative state after a car accident in 2005. At the time of the study, five months had elapsed since her accident, meaning that statistically, she had a 20 percent chance of some recovery. She showed no outward signs of awareness.

The results of the test were shocking, even "spectacular," according to a commentary accompanying their publication in the journal Science last fall. "When we cued her with the word 'tennis,' her brain would activate in a way that is indistinguishable from a healthy person," says Owen. The same was true for the word "house." "We think the fMRI demonstrated unequivocally that she is aware," he says.

While the patient met all the clinical requirements for being in a vegetative state, her fMRI clearly showed a brain capable of relatively complex stimulus-processing. Still, it's not yet certain what conclusions can be drawn from her case. "We have studied over 60 patients in Belgium and have never seen activation compatible with conscious perception," says Laureys. "I definitely think this is the exception, but I can't tell if it's a one-in-a-thousand or a one-in-a-million case." Owen now plans to run the same tests on more patients, using a variation of fMRI that shows brain responses in real time.

Perhaps the most perplexing question raised by the results concerns the patient's state of mind: is she truly conscious? That's a matter of some debate: Owen believes the patient was aware of herself and her surroundings, but other neurologists aren't so sure. "No one knows what she really was thinking during scanning," says Laureys.

The answer may come with Owen's next round of experiments, which are designed to perform what some consider the best test of consciousness--asking a person about his or her state of mind. Using real-time fMRI, scientists can ask patients questions and gauge their responses on the basis of their brain activity. For example, since scientists know the activity patterns associated with imagined games of tennis and walks through houses, they could tell their patients to think of tennis for yes and house tours for no, then ask binary questions while performing brain scans.

Like Schiff and Hirsch's findings, Owen's are both fascinating and disquieting, largely because neurologists don't yet know what to do with them. Does the brain activity of the woman Owen studied mean she will soon wake up? What about other patients with similar injuries? Schiff, for one, plans to see if some of his patients who show visible signs of awareness can replicate Owen's results. "My guess is that some of them will be able to do it," he says.