Study: Why Deafness May Improve Vision

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Jose Luis Pelaez, Inc./Blend Images/Corbis

Scientists have long known that deaf or blind people have heightened senses outside of their impairment. But what hasn’t been clear is how the mechanics of a compensating sense work.

Now a neurological study of cats in the October 12 edition of Nature Neuroscience helps explain the phenomenon. In the study of deaf animals, researchers found that brain regions that would normally have assisted in hearing were taken over and used to enhance vision instead. As Wired reported, this may correspond to how deaf people are able to detect movement and peripheral activity better than sighted people:

“There have been all these theories out there for what region of the brain might be responsible for this, but no one has actually gone in there and demonstrated it,” [head investigator Stephen] Lomber says. Since cat brains are organized much like human brains, the results may mirror what happens in the brain of a deaf person.

Deaf cats don’t have better overall vision than their hearing counterparts, the researchers found. Rather, like deaf humans, the cats are better at two particular visual tasks — seeing objects in far peripheral vision and detecting very slow motion. These particular enhancements might help deaf people assess their surroundings more accurately: “You can’t hear the dog running or the car coming at you, so being able to see it seems like a really good skill,” says Lomber, of the University of Western Ontario in London, Canada.

When the researchers disabled specific parts of the cats’ brains that were related to hearing, the cats lost corresponding visual skills: so, for instance, when the region responsible for localizing sounds was inactivated, so was the animals’ peripheral supervision. The study focused on cats that were born deaf, so it is unclear if those with degenerative hearing would experience the same neurological shift. Additional studies will be needed to determine if other senses, such as touch, taste and smell are also affected.

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