Human Echolocation - Neural Substrates of Echolocation in The Blind

Neural Substrates of Echolocation in The Blind

Some blind people are skilled at echolocating silent objects simply by producing mouth clicks and listening to the returning echoes. It has been recently shown that blind echolocation experts use what is normally the ‘visual’ part of their brain to process the echoes. The researchers first made recordings of the clicks and their very faint echoes using tiny microphones placed in the ears of the blind echolocators as they stood outside and tried to identify different objects such as a car, a flag pole, and a tree. The researchers then played the recorded sounds back to the echolocators while their brain activity was being measured using functional magnetic resonance imaging. Remarkably, when the echolocation recordings were played back to the blind experts, not only did they perceive the objects based on the echoes, but they also showed activity in those areas of their brain that normally process visual information in sighted people, primarily primary visual cortex or V1. Most interestingly, the brain areas that process auditory information were no more activated by sound recordings of outdoor scenes containing echoes than they were by sound recordings of outdoor scenes with the echoes removed. Importantly, when the same experiment was carried out with sighted people who did not echolocate, these individuals could not perceive the objects and there was no echo-related activity anywhere in the brain.