A new study claims that in blind people, the parts of brain that are used for processing vision, are recruited for language processing.
The find by MIT neuroscientists shows that the visual cortex can dramatically change its function and disproves that language processing can only occur in highly specialized brain regions that are genetically programmed for language tasks.
"Your brain is not a prepackaged kind of thing. It doesn't develop along a fixed trajectory, rather, it's a self-building toolkit. The building process is profoundly influenced by the experiences you have during your development," said Marina Bedny.
Bedny and her colleagues scanned blind subjects (using functional magnetic resonance imaging) as they performed a sentence comprehension task.
The researchers hypothesized that if the visual cortex was involved in language processing, those brain areas should show the same sensitivity to linguistic information as classic language areas such as Broca's and Wernicke's areas.
The results confirmed their theory.
"The idea that these brain regions could go from vision to language is just crazy. It suggests that the intrinsic function of a brain area is constrained only loosely, and that experience can have really a big impact on the function of a piece of brain tissue," said Bedny.
She added that the research does not refute the idea that the human brain needs Broca's and Wernicke's areas for language.
"We haven't shown that every possible part of language can be supported by this part of the brain [the visual cortex]. It just suggests that a part of the brain can participate in language processing without having evolved to do so," she says.
The team now plans to find out why the visual cortex would be recruited for language processing, when the language processing areas of blind people already function normally.
The researchers are also working to pinpoint more precisely the visual cortex's role in language processing.
The study appears in the Proceedings of the National Academy of Sciences the week of Feb. 28.