Brain chat (Image: Studio Tonne/Agency Rush.com)

STEVEN LAUREYS will always remember the 21-year-old woman who had had a stroke. She had been taken to a hospital in Liège, Belgium, where her condition worsened rapidly. She soon lost all motor movement, even the ability to open her eyes. Her prognosis looked bleak, so her doctors turned to Laureys, a neurologist, for a final opinion before turning off her ventilator.

By recording her brain activity as she was asked to respond to simple tasks, such as counting the number of times her name was spoken in a random string of first names, Laureys confirmed that the woman was aware of her surroundings, and so she remained on life support (Neurocase, vol 15, p 271). Clearly that was the right decision: a year later she had recovered enough to be discharged from hospital. “It was only technology that permitted us to show that she was conscious,” says Laureys of the University of Liège.

There had, however, been another clue to the patient’s active mental state – too tentative to hold any weight in the diagnosis, but nevertheless significant. Laureys had observed a signature of coordinated neural activity, present in the resting patient, which seems to appear in the brain of anyone who is conscious. While such readings may one day provide a better diagnosis of coma patients, their ultimate implications may be even more profound, providing evidence for a 30-year-old theory that claims to explain consciousness itself.

Consciousness is one of neuroscience’s long-standing mysteries. At its most basic, it is the simple question of why we become aware of some thoughts …