In blind people, areas of the brain that would normally process visual information do not simply pack up and disappear. Instead, they find new work processing language-related information, reveal new findings to be published in the November issue of Nature Neuroscience.
Previous brain imaging studies had shown that in blind people, visual brain areas are active during language-related tasks. However, it was not known whether this activity was actually necessary for language processing. Leonardo Cohen and colleagues asked blind and sighted subjects to respond to a noun with an appropriate matching verb as quickly as possible (e.g., say? eat? when they hear 'apple'). While the subjects were performing this simple task, the researchers used a technique called transcranial magnetic stimulation to disrupt brain activity in visual cortex. In sighted individuals, this manipulation had no effect. Blocking visual cortex activity in blind subjects, however, caused them to be less accurate in generating an appropriate verb. This was not due to an impairment in the ability to say words, but rather was due to an inability to think of the correct verb (a semantic error).
In the current study, all of the blind individuals had lost their sight early in life; it remains unclear whether a similar reorganization of the brain occurs in people who lose their sight at later ages.
Leonardo Cohen (NINDS, NIH, Bethesda, MD, USA)
Tel: +1 301 496 9782
Also available online.
(C) Nature Neuroscience press release.
Message posted by: Trevor M. D'Souza