Human Echolocation: Blind Individuals Use Different Regions of Their Brains

Did you know humans can use echolocation? Those who are blind sometimes learn to use echoes from tongue or finger clicks to navigate their world. Now, scientists have taken a closer look and have found that people who use echolocation actually use regions of their brain normally associated with visual perception.

"Our experiments show that echolocation is not just a tool to help visually impaired individuals 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, one of the researchers, in a news release. "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."

Sighted individuals use visual cues to get information about the composition of objects. For example, they recognize the sheen of metal, or the fuzziness of fur. In contract, echolocators must use auditory cues that result from the echoes of the clicks that they emit.

In order to examine how the brains of echolocators process these sounds, the researchers recorded the echoes produced by echolocators' clicks. Then, the scientists used functional magnetic resonance imaging (fMRI) to see which brain regions were activated in these individuals.

The researchers found 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. PHC activation is associated with scene perception in sighted individuals. Just as in sighted individuals using vision, the brain regions that play a critical role in processing the structure and geometry of objects are distinct from the brain regions that process the cues that signal the material properties of objects in blind echolocators.

The findings reveal a bit more about echolocation. This is important since echolocation itself can be used as an important tool to help blind individuals navigate the world around them.

The findings were presented at the 9^th Annual Canadian Neuroscience Meeting.

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