Everybody has heard about echolocation in bats and dolphins. These creatures emit bursts of sounds and listen to the echoes that bounce back to detect objects in their environment. What is less well known is that people can echolocate, too. In fact, there are blind people who have learned to make clicks with their mouths and to use the returning echoes from those clicks to sense their surroundings. Some of these people are so adept at echolocation that they can use this skill to go mountain biking, play basketball, or navigate unknown environments.
Researchers at Western's Centre for Brain and Mind have recently found evidence that blind echolocation experts use what is normally the 'visual' part of their brain to process the clicks and echoes. This study, which appears this month in the scientific journal, PLoS ONE, is the first to investigate the neural basis of natural human echolocation.
The researchers first made recordings of the clicks and their very faint echoes using tiny microphones 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 in Western's state-of-the-art fMRI brain scanner. 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. 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 control people who did not echolocate, these individuals could not perceive the objects, and neither did their brain show any echo-related activity.
As lead author Lore Thaler, postdoctoral fellow at Western, explains "this suggests that visual brain areas play an important role for echolocation in blind people".
Co-author, Stephen Arnott, Scientific Associate at the Rotman Research Institute in Toronto, adds "there is the possibility that even in sighted people who learn to echolocate, visual brain areas might be recruited".
Since the study was the first of its kind, this question, like many others, remains to be investigated in future research. But as senior author Mel Goodale, Canada Research Chair in Visual Neuroscience, explains "even at this point, 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".
Funding: This work was supported by the Canadian Institutes of Health Research (MAG) and the Ontario Ministry of Research and Innovation (LT). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Citation: Thaler L, Arnott SR, Goodale MA (2011) Neural Correlates of Natural Human Echolocation in Early and Late Blind Echolocation Experts. PLoS ONE 6(5): e20162. doi:10.1371/journal.pone.0020162
Journal
PLoS ONE