"The Neural Correlates of Echolocation in the Blind"
Dr. Melvyn Goodale, The University of Western Ontario
Monday, February 6th at 5:30 p.m., 118 Psychology
"I can hear a building over there"
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 mouth and tongue – and to use 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. In this talk, we will learn about several of these echolocators – some of
whom train other blind people to use this amazing skill.
Using fMRI we showed that blind echolocation experts use what is normally the ‘visual’ part of
their brain to process the clicks and echoes. We first made recordings of the clicks and their
very faint echoes using miniature microphones inserted in the ears of the blind echolocators as
they identified different objects. We then played the recorded sounds back to the echolocators
in the scanner. Remarkably, when the echolocation recordings were played back to the blind
experts, not only did they perceive the objects based on the distinctive echoes, but they also
showed activity in the calcarine cortex, a brain area corresponding to primary visual cortex in
sighted people. This activation was particularly striking in the blind echolocator who had lost
his vision early in life. Interestingly, auditory cortical areas were no more activated by sound
recordings of outdoor scenes containing echoes than they were by sound recordings of outdoor
scenes with the echoes removeds – even though the ‘visual’ brain areas were remarkably
sensitive to the faint echoes. When the same experiment was carried out with sighted people
who could not echolocate, these individuals could not make sense of the clicks and echoes, and
neither did their brains show any echo-related activity. This study raises many questions about
neuroplasticity and sensory substitution. But 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.
Suggested Readings
Teng, S. and Whitney, D. (2011). The acuity of echolocation: Spatial resolution in the sighted
compared to expert performance. J Vis Impair Blind, 105(1). [.pdf]
Thaler, L., Arnott, S., and Goodale, M. (2011). Neural Correlates of Natural Human Echolocation in Early
and Late Blind Echolocation Experts. PLoS ONE, 6(5). [.pdf]