Blind people use echoes to detect matter: Study

Blind people use echoes to detect multiple properties of objects through areas of the brain associated with vision, new study says.

Certain blind people can use echoes from tongue or finger clicks to recognize objects in the distance and some use echolocation as a replacement for vision.

"Our experiments show that echolocation is not just a tool to help blind people navigate their environment, but can act as an effective sensory replacement for vision, allowing them to recognize the shape, size, and material properties of objects," said Mel Goodale from the University of Western Ontario, Canada.

Many of the same regions in the sighted brain that are used for the visual assessment of objects are recruited in the blind brain when objects are explored using echolocation.

"Remarkably, expert blind echolocators can tell whether something is hard or soft, dense or not, just by listening to the echoes bouncing back from that material," Goodale noted.

Whereas sighted individuals use visual cues to get inputs about the composition of objects, echolocators must rely on the auditory cues that result from the echoes of the clicks they emit.

Researchers have recorded the echoes produced by echolocator's clicks on different materials to determine how the brains of echolocators process these cues.

To view which brain regions were activated in these individuals, an advanced brain imaging technique called functional magnetic resonance imaging (fMRI) was used.

These studies show that material-related signals activate a region of the brain called the parahippocampal cortex (PHC) in blind expert echolocators, but not in sighted people or blind non-echolocators.

The results were presented at the 9th Annual Canadian Neuroscience Meeting in Vancouver British Columbia.