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The Blind Use the Visual Cortex to Process Sound

Recent research has confirmed that in blind subjects who use echolocation to navigate, it is the visual part of the brain that processes the auditory echoes. Christie Nicholson reports

 

Some bats with poor eyesight depend on echolocation to navigate. They emit squeaks and gauge their environment based on the echo returned. Dolphins and shrews use it, too. And humans.

A few blind people have mastered echolocation in order to sense their surroundings. One famous example, Ben Underwood—who lost his sight when he was two—could skateboard, run, even play basketball by clicking his tongue rapidly.

And now scientists have learned that the area of the brain that processes the echoes is not the region for hearing—it’s actually the visual cortex. The research is in the journal Public Library of Science ONE.

Two blind subjects used clicks and their echoes to distinguish objects like a car, tree or flagpole. Researchers made recordings of the echoes with tiny microphones placed inside subjects’ ears. Then they studied the subjects’ brain activity while they played back the recordings.

The subjects were not only able to tell which objects matched which echo pattern, but the brain tracking revealed the visual cortex activity when the subjects heard the echoed clicks. Sighted subjects showed no such activity. And once again we learn that the brain is far more flexible than it thought.

—Christie Nicholson

 

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