If you could choose one superpower, what would it be? It’s fun to dream about flying like Superman, but some blind people don’t have to dream about having a superpower. They have an amazing sense of echolocation that enables them to navigate cities, go mountain biking, and play basketball using reflected sound waves. A recent study led by Dr. Melvyn Goodale at the University of Western Ontario investigated what brain regions are active during natural human echolocation. The findings may surprise you!
Natural echolocation is the process of making a sound, usually a 'click,' and identifying nearby objects by listening to the reflected sound waves. The time it takes for these echoes to return depends on how far away an object is. The acoustic quality of the echoes depends on the object’s shape and texture. Although it’s typically attributed to bats and dolphins, echolocation is a skill that can be learned by humans and is being highly developed by the blind.
Did you know? It has been known since the 1940s that blind people use sound to identify silent objects.
Dr. Goodale’s lab recruited two blind people who currently use echolocation (through tongue 'clicks') to identify the shape, size and movement of objects with astonishing accuracy. The research team then used functional magnetic resonance imaging (fMRI) to determine which brain areas were active during echolocation. Since people have to be perfectly still inside an fMRI machine, the scientists pre-recorded the clicks and echoes while the subjects were echolocating, then used earphones inside the fMRI machine to play the recordings back. They also conducted the same test on two sighted people.
Did you know? fMRI uses a strong magnetic field and radio waves to measure blood oxygenation levels in different regions of the brain – higher blood oxygen means increased brain activity.
As you might expect, for the sighted people, the most active brain region during the 'clicks' was in the auditory cortex, the part of the brain responsible for processing sound. However, for the blind people, the auditory cortex and the visual cortex (that part of the brain typically responsible for sight) were both activated! It’s still not known exactly how the visual cortex facilitates human echolocation, but activity in this region is clearly not dependent on input from the eyes.
Did you know? The two study subjects, Daniel Kish and Brian Bushway, teach echolocation (they call it FlashSonar) to other blind people through an organization called World Access for the Blind.
You can think of human echolocation as “seeing” echoes to create a mental picture of the world. It's allowing blind people to ride mountain bikes, navigate cities and play soccer–pretty cool for a real-life superpower!
The brain on sonar - how blind people find their way around with echoes
Discovery Channel - Is it possible: Real-life Batman
Wired - Make Like a Dolphin: Learn Echolocation
Bats & Echolocation
How fMRI works
The original research paper from the online journal PLoSONE:
Thaler L, Arnott SR, Goodale MA (2011) Neural Correlates of Natural Human Echolocation in Early and Late Blind Echolocation Experts. PLoSONE 6(5): e20162. doi:10.1371/journal.pone.0020162 (http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0020162)
An excellent PLoS blog article about human echolocation:http://blogs.plos.org/neuroanthropology/2011/06/14/getting-around-by-sound-human-echolocation/
First published July 25, 2011