Researchers have been able to solve a long standing mystery about the deaf and their extraordinary vision.
Scientists have been able to establish the reason why some deaf people tend to have a superior peripheral vision. In a study done on deaf cats (as their brains are organized just like humans’), they found that the brain regions usually responsible for hearing get ‘co-opted’ to the visual system, thus augmenting the vision. However, the deaf cats didn’t have better overall vision; instead they were found to have greater peripheral vision and motion detection, which perhaps explains why deaf people are able to assess their surroundings much more accurately.
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After establishing that these two visual abilities [seeing objects in far peripheral vision and detecting very slow motion] were enhanced in deaf cats, Lomber and his team tested whether hearing-related brain areas were responsible for the boost. With the help of a 3-millimeter-wide cooling device, the researchers inactivated very particular regions of the cats’ auditory cortices. The coil sits on the outside of the brain and induces a precisely localized hypothermia, causing the region to effectively shut down until the device is turned off.
Deaf cats with chilled hearing-related brain regions lost their visual edge, and in a very specific way. “What we found was, much to our surprise, that these functions were not distributed randomly over the auditory cortex, but they were specifically localized in particular places,” Stephen Lomber of University of Western Ontario says.
For instance, when a brain region that is normally important for localizing auditory signals was shut off, the deaf cats lost their superior ability to spot a laser that flashed in the far periphery of their visual fields, the team found. “It seems that if there’s no auditory stimulation, the auditory cortex was still doing what it would normally do, but with a different sensory input — in this case, vision,” Lomber says.