The visual cortex can learn to do speech and language

It’s been known for well over a century that different parts of the brain handle different tasks. This was certainly true for the autonomous functions, such as breathing and hormone activity, but it was also apparently true for higher level functions such as speech and language. Two regions of the brain, Broca’s area and Wernicke’s area are known to be necessary for speech production and language capacity. It’s long been thought that they have specific neuron patterns and nerve connections, which makes them language specialists. In a similar way for hearing, sight, smell, and touch it was thought that specific areas of the brain were involved – more or less exclusively. It’s that last bit, ‘more or less exclusively,’ that is now in doubt.

Research by Marina Bedny and colleagues at the Massachusetts Institute of Technology (USA) and published in the Proceedings of the National Academy of Sciences, 28 February 2011 [Language processing in the occipital cortex of congenitally blind adults] has shown that in people born blind, part of the visual cortex is converted to language processing.

It’s important to understand that this does not mean language and speech can be produced without Broca’s or Wernicke’s areas, but it does mean that other parts of the brain previously thought dedicated to a specific function can be marshaled for other purposes. The implications are many and important. This discovery, born out by fMRI (functional magnetic resonance imaging) of brain areas in people born without sight, implies that even very complex so-called higher level functions such as language, can be performed by ‘non-language-specialist’ regions of the brain.

In fact, it is part of a follow-up study by the research group to see if the additional brain cells acquired from the visual cortex may give blind people certain advantages in language processing. It’s a matter of common observation that people who have lost one of their senses tend to have one or more of the other senses strengthened. This was born out by research, for example from animal studies by Mriganka Sur (also at M.I.T.), where brain regions were surgically rewired early in life, and the brain cells eventually adapted to the new role. However, the Bedny study is the first to indicate the same thing can happen with more complex mental processes.

They found that was indeed the case — visual brain regions were sensitive to sentence structure and word meanings in the same way as classic language regions, Bedny says. “The idea that these brain regions could go from vision to language is just crazy,” she says. “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.”

[Source: EurekAlert]

In short, this is another piece of evidence that the brain is more flexible than thought. The word is plastic, flexible. Under certain conditions, the brain can do extraordinary things by way of rerouting neuron circuits, changing or developing different neuron patterns, and coordinating previously unconnected regions. It’s almost ironic that the tool that has done the most to help neuroscientists isolate the functioning of brain regions, the fMRI, is now showing that the concept of dedicated brain regions needs something of a re-think.

Research Spectrum

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