Sight Gets Repurposed in Brains of the Blind

In the brains of people blind from birth, structures used in sight are still put to work — but for a very different purpose. Rather than processing visual information, they appear to handle language.

Linguistic processing is a task utterly unrelated to sight, yet the visual cortex performs it well.

“It suggests a kind of plasticity that’s even broader than the kinds observed before,” said Marina Bedny, a cognitive neuroscientist at the Massachusetts Institute of Technology. “It’s a really drastic change. It suggests there isn’t a predetermined function an area can serve. It can take a wide range of possible functions.”

In a study published Tuesday in the Proceedings of the National Academy of Sciences, Bedny’s team monitored the brain activity of five congenitally blind individuals engaged in language-intensive tasks.

Immense neurological plasticity was suggested by research conducted in the late 1990s on “rewired” ferrets — after their optical nerves were severed and rerouted into their auditory cortices, they could still see — but such studies, already ethically troubling in animals, would be unconscionable in humans.

Instead, researchers have used brain imaging to study plasticity resulting from natural sensory deprivation in people. They’ve found that the visual cortices of blind people become active as they read Braille. It wasn’t clear, however, whether this was a function of Braille’s spatial demands, which overlap with the spatial aspects of sight, or a radical repurposing of supposedly specialized areas.

Wired Science

Photo of Stevie Wonder by Al Satterwhite