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Visual cortex recruits language processors to understand language in those who were born blind  (Source: broadcast.oreilly.com)
The visual cortex in the brain is capable of processing language in those who were born blind

Marina Bedny, study leader and an MIT postdoctoral associate in the Department of Brain and Cognitive Sciences, along with a team of researchers including Rebecca Saxe, assistant professor of brain and cognitive sciences at MIT, and Alvaro Pascual-Leone, professor of neurology at Harvard Medical School, have found that the visual cortex, which is responsible for visual processing, can also change its function to language processing.  

The brain transports input from sensory stimuli, such as the scent of a candle or the sound of a whistle, to the appropriate region in the brain for analysis. The smell of the candle is sent to the olfactory cortex, and the sound of the whistle is sent to the auditory cortex. This process suggests that the brain follows a genetic blueprint, but recent studies are starting to show otherwise.

For example, a study in 1996 showed that people who became blind early in life were able to understand non-visual functions, like reading Braille. But this only showed that there was activity in the left visual cortex and did not show whether this involved "full-fledged language processing."

Now, the MIT research team has found that the visual cortex can change its function and recruit certain parts of itself specifically for language processing, making those who are born blind capable of understanding language. This contradicts the traditional idea that language processing can only occur in specialized areas of the brain specifically programmed for language. 

Neuroscientists have known for more than a century that Broca's area and Wernicke's area are two regions in the brain necessary for producing and understanding language. It was thought that these two areas were specifically mapped out for these purposes only, and that senses like vision and hearing were specifically assigned to processing centers in the sensory cortices. But now, the MIT research team has found that the brain is flexible when assigning functions to certain areas, and for the first time, evidence is available for flexibility in language processing. 

The MIT team researched whether certain regions in the brain in blind people could allow them to understand word meanings and sentence structure. To do this, they scanned the blind test subjects using functional magnetic resonance imaging while giving them a sentence comprehension task. What they found was that the visual cortex showed the same sensitivity to language comprehension as Broca's and Wernicke's areas, proving that the visual cortex can change functions from processing images to processing language. 

"It suggests that the intrinsic function of a brain area is constrained only loosely, and that experience can have a really big impact on the function of a piece of brain tissue," said Bedny. "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."

One question left unanswered through this research is why blind people would need the visual cortex to participate in language processing when the Broca's and Wernicke's areas function normally. Bedny theorizes that it may be due to a redistribution of tasks during development of the brain. 

"As these brain functions are getting parceled out, the visual cortex isn't getting its typical function, which is to do vision," said Bedny. "And so it enters this competitive game of who's going to do what. The whole developmental dynamic has changed."

The next step in the MIT team's research is to study blind children in order to figure out when the visual cortex begins processing language during development. 

This study was published in Proceedings of the National Academy of Sciences.





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