Verbal sighting in brains of the blind

Science News, Oct 16, 2004

Brain areas that typically play a key role in vision instead contribute to language skills among blind people, a new study finds. This observation underscores the brain's ability to adapt to individual circumstances, say Leonardo G. Cohen of the National Institute of Neurulogical Disorders and Stroke in Bethesda, Md., and his colleagues.

The scientists administered a verbal task to nine adults with normal sight and nine adults who had lost their sight by age 4. Each volunteer listened to a series of spoken nouns, such as apple, and had 5 seconds after each one to say an appropriate verb, such as eat.

In some trials, the researchers temporarily disabled various brain regions by briefly transmitting focused magnetic pulses through the volunteers' skulls. Only blind volunteers made a large number of mistakes on the verbal task--such as responding to apple with jump--when the pulses disabled either of two rear-brain regions. In sighted individuals, these structures participate in early stages of visual processing.

Sighted participants erred frequently on the task only after the magnetic pulses temporarily sidelined a frontal-brain area previously implicated in verbal skills. Pulses to that area didn't affect the blind volunteers, the researchers report in the November Nature Neuroscience.--B.B.