Blind people's brains rewire themselves to help them track moving objects by sound, study shows

‘Enhanced’ hearing allows the visually-impaired to tune into subtle changes of frequency to track movements

Alex Matthews-King
Health Correspondent
Monday 22 April 2019 20:16
Blind boy Sam demonstrates how to Echolocate

Blind people's brains rewire themselves to allow them to track moving objects by sound, a study has found.

For the first time, scientists have shown how changes in the brain explain improvements to other senses – a phenomenon that has inspired comic book superheroes like the Marvel character Daredevil.

Some visually impaired people are able to train themselves to use clicks as a type of echolocation to detect obstacles.

The latest research from the University of Oxford and a number of US universities tracked people who were blind at birth or lost their sight as children.

They found their increased abilities may be possible because their hearing is much more finely tuned to variations in frequency.

Anyone who has heard a passing ambulance or police siren will be familiar with the way the sound appears to change pitch.

This phenomenon, known as the Doppler effect, is caused by a relative change in frequency of the soundwaves.

Being tuned into subtle differences in everyday noises may help blind people interpret their surroundings.

“For a sighted person, having an accurate representation of sound isn’t as important because they have sight to help them recognise objects, while blind individuals only have auditory information,” said Kelly Chang, one of the study's authors from the University of Washington.

“This gives us an idea of what changes in the brain explain why blind people are better at picking out and identifying sounds in the environment.”

The findings are published in two papers. One study in the Journal of Neuroscience used MRIs to scan the brain activity of blind subjects and test how finely tuned their neurons were to subtle changes in frequency.

The second study, published in the journal Proceedings of the National Academy of Sciences, looked at how a region of the brain devoted to tracking moving visual objects in sighted people is rewired to focus on tracking these auditory movements.

Researchers also studied two people who had been blind from infancy but had their sight restored thanks to surgery as adults. In these cases, this tracking region of the brain, known as hMT+, was able to perform this role for visual and auditory movements.

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Professor Ione Fine, a psychologist at the University of Washington and senior study author, said this was the first study to show these changes in the auditory cortex.

She said: “This is important because this is an area of the brain that receives very similar auditory information in blind and sighted individuals. But in blind individuals, more information needs to be extracted from sound – and this region seems to develop enhanced capacities as a result.

“This provides an elegant example of how the development of abilities within infant brains is influenced by the environment they grow up in.”

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