Blind can develop bat-like sonar to see
May 26th, 2011 - 3:26 pm ICT by IANSLondon, May 26 (IANS) Blind people can develop ’sonar’, learning to navigate like bats by ’seeing’ objects from sounds reflected off them.
Some become so skillful at listening to the returning echoes of clicking noises that they make with their mouths that they can use their ability to go mountain biking or play ball games.
It is well known that bats use a biological version of sonar, called echolocation, to find their way around at night. That blind humans could do it too was suspected but not known.
Now Canadian researchers led by Mel Goodale, from the University of Western Ontario, have proved that they can. Intriguingly, they do so by using a part of the brain normally involved in processing visual images, reports the journal Public Library of Science One.
“It is clear that echolocation enables blind people to do things that are otherwise thought to be impossible without vision, and in this way it can provide blind and vision-impaired people with a high degree of independence in their daily lives,” said Goodale.
They discovered this by carrying out brain scans on two male volunteers, aged 43 and 27, who had both been blind since childhood, according to the Telegraph.
Each was asked to stand outside and try to perceive different objects such as a car, a flag pole and a tree by making clicking noises and then picking up their very faint echoes.
Tiny microphones were placed in the volunteers’ ears to record the outgoing and incoming sounds.
The men later had these sounds played back to them, while their brain activity was monitored using functional magnetic resonance imaging (fMRI) scans.
During playback, they were able to identify which object was which from the echoes alone. The fMRI scans showed that these echoes were being processed by brain regions normally used to process visual information.
No echo-related activity was seen in the auditory brain areas, which would be expected to process sound.
The 43-year-old, who lost his sight earlier, performed better. His eyes were removed at 13 months due to a rare cancer called retinoblastoma.
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