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Rewired for Consciousness?
3 July 2006 (All day)
In 2003, 39-year-old Terry Wallis spoke his first words in 19 years. Speechless since a car accident severely damaged his brain, Wallis quickly regained consciousness and began interacting with those around him. His astonishing recovery made headlines worldwide. Now, researchers have published a set of brain scans that suggest Wallis's brain underwent a major rewiring after his accident that may have played a role in his comeback.
For nearly 2 decades, Wallis languished in what doctors call a minimally conscious state; he would respond only sporadically--and then only with grunts and nods--to those around him. His family now says he's basically back to his old self, except for some speech and memory difficulties, says Nicholas Schiff, a neurologist at Weill Medical College of Cornell University in New York City and senior author on the new paper.
Schiff and colleagues first examined Wallis in April 2004, about 8 months after he began speaking. They used a relatively new technique called diffusion tensor imaging that provides information about the brain's white matter, the tracts of axons that serve as communication links between brain regions. This first set of scans revealed thick cables of axons linking the left and right hemispheres at the back of the brain. These connections were far more pronounced in Wallis's brain than in a group of 20 healthy subjects, and the regions of cerebral cortex they connected appeared to be more active than normal, according to a positron emission tomography scan, Schiff and colleagues report in the July issue of the Journal of Clinical Investigation.
A second examination, in October 2005, revealed stronger than normal connections and neural activity in Wallis's cerebellum, a brain region important for movement and coordination. That finding is especially tantalizing because those functions improved substantially in the time between the first and second exams, Schiff says. All in all, he says, the findings suggest that the brain regions that survived Wallis's accident forged new connections, perhaps in an attempt to re-establish contact with regions that were damaged.
While Wallis's case is extraordinary, it adds to other recent evidence that the adult brain may have more capacity to reorganize after injury than many researchers have assumed, says Steven Laureys, a neurologist at the Université de Liège in Belgium. The study also suggests that "we really should be using more cutting edge imaging methods in these patients," says Adrian Owen, a neuroscientist at the Medical Research Council Cognition and Brain Sciences Unit in Cambridge, United Kingdom. More work like this is needed to develop clinical tools that can determine which patients are most likely to recover and which are most likely to benefit from various types of rehabilitation, Owen says.