Image caption The auditory cortex in the brain usually processes sound

People deaf from birth may be able to reassign the area of their brain used for hearing to boost their sight, suggests a study.

Improved peripheral vision, often reported by deaf people, could be generated by the brain area which would normally deal with peripheral hearing.

The Canadian research, published in the journal Nature Neuroscience, tested the theory using congenitally deaf cats.

The researcher involved said the brain did not let unused space "go to waste".

Both deaf and blind people frequently say their other senses are sharper by way of compensation.

However, it has not been obvious how the brain might achieve this.

Compensation

The researchers from the University of Western Ontario used their cat studies to test which parts of the brain were responsible.

The brain is very efficient, and doesn't let unused space go to waste Dr Stephen Lomber, Researcher

Their cats were given tests in which lights flashed at the very periphery of their normal vision.

When only the auditory cortex - the part of the brain which normally processes sound information - was deactivated temporarily, their enhanced peripheral vision appeared to be switched off as well.

Narrowing the search, the team found that the part of the auditory cortex responsible was the part which would ordinarily detect peripheral sounds.

Dr Stephen Lomber, who led the research, said: "The brain is very efficient, and doesn't let unused space go to waste.

"The brain wants to compensate for the lost sense with enhancements that are beneficial.

"For example, if you're deaf, you would benefit by seeing a car coming far off in your peripheral vision, because you can't hear that car approaching from the side - the same with being to more accurately detect how fast something is moving."

He said that understanding what happens within the auditory cortex in the absence of sound information coming in could help doctors work out what is happening when someone with hearing loss is given a cochlear implant.

"If the brain has rewired itself to compensate for the loss of hearing, what happens when hearing is restored?"

Reaction time

Dr Joanna Robinson, a researcher at the Royal National Institute for Deaf People (RNID), welcomed the findings.

She said: "This research supports previous findings that people who are deaf from birth have a larger visual field than hearing people.

"Research funded by ourselves recently showed that deaf adults can also react to objects in their peripheral vision more quickly than hearing adults, while deaf children react more slowly than their hearing counterparts.

"This indicates that it may take some time for the auditory part of the brain to make the switch to processing visual information."