Seeing through sound: How a tongue click gave one man independence
By Heather Travis
May 13, 2011
Watching Daniel Kish climb aboard a bicycle and pedal along a path may not seem like a spectacular feat. Unless you know he has been fully blind since 13 months of age.
Kish has developed an amazing ability to navigate by echolocation – similar to bats and dolphins. It’s a skill University of Western Ontario researchers are just now starting to understand.
Kish’s eyes were removed in infancy due to retinal tumors. Even before the age of 2, he started making a clicking noise by striking his tongue against his palette. But it wasn’t until he was 10- or 11-years-old when a friend explained to him how sonar worked and the relationship between his click and navigation.
“People used to call it my ‘radar,’” he says. “I’ve been echolocating for as long as I can remember.”
His reliance on echolocation was driven home when he was fitted with an orthodontic retainer at 15 and could not produce a click for several days. At the time, he walked to school by himself.
“I mean, my click, it was everything. And then, I wasn’t able to click and it was just a real, huge, unbelievable bother,” he says. “And it took me several days to get to the point where I could strike a click off my plastic retainer and have it be a click I could recognize.”
While many blind people use a form of echolocation, Kish says, his method is unique and referred to as “flash sonar.”
Think of Kish’s ability like a bat’s sonar call. Bats emit a high-pitched sound while flying in the night sky. The sound waves bounce off an object (such as an insect) and send an echo back. Just as light waves provide information to our eyes for our brain to interpret, similarly the echo sound waves have impressions from the objects they bounce off of. Like flashes of light, the sounds illuminate the environment acoustically, rather than optically.
“You can hear those imprints. You can hear the differences in the sound waves as they come back,” he says. “So basically what you can do is extract information now imbedded in those sound waves. That information corresponds to the surfaces from which the sound waves bounce.
“It sounds complicated, but it’s not really. It’s exactly the same as light waves do. It’s exactly how vision works.”
The information may not be quite as detailed as what is provided from visually ‘seeing’ things, but Kish can detect location, dimension and depth of structure (such as how absorbent, reflective, solid or sparse an object is). His interpretations of the echoes are also informed by experience and language.
As president of World Access for the Blind, Kish has taught hundreds of blind students how to use flash sonar.
But over the years Kish has faced his share of critics who argue the legitimacy of his abilities.
“The paradigm for understanding human perception and human neurology is very, very sight-centric,” he says. “We basically need to establish a strong paradigm that supports the idea that the human sensory system is adaptable and malleable, and that the eyes are only one way to see – only one way to image.”
Echolocation has some advantages over sight. You can hear through and around things. Hearing is a 360-degree sense, whereas vision is limited to 180 degrees. As well, auditory information is processed more quickly than visual data, he says.
To help prove his case, Kish agreed to be put under a microscope – or a 3T functional magnetic resonance imaging (fMRI) machine to be exact – at Western.
The California resident was introduced to Mel Goodale, Canada Research Chair in Visual Neuroscience and Western’s Centre for Brain and Mind director, through a mutual friend and ophthalmologist in Glasgow, Scotland. Goodale, along with post-doctorate students Lore Thaler and Stephen Arnott, invited Kish and fellow echolocator Brian Bushway to campus in fall of 2009 to study the neurology of echolocation.
“As vision is lost early on, the brain reorganizes itself,” says Thaler, meaning the brain is making use of unused ‘real estate’ otherwise dedicated to vision.
“(Kish’s) visual cortex is being subsumed by information that is apparently coming in from his ears,” Goodale adds.
Bushway is a protégé of Kish. He lost his sight in his early teens and was taught by Kish to echolocate.
In order to conduct the scans in the fMRI, the researchers had to pre-record the clicks produced by Kish and Bushway. The noise of the fMRI scanner would prevent them from hearing their own clicks. As well, the subject must be completely still in order to produce an accurate scan.
The pair entered the Beltone Anechoic Chamber at the National Centre for Audiology located at Elborn College. The chamber absorbs sound so an echo is not produced making it the ideal controlled environment to test the men’s ability.
The researchers inserted tiny microphones into the ears of the two subjects to record both the click and the echo. They were tested on the localization of a pole, shape discrimination of flat, concave and convex surfaces as well as motion detection. They also recorded clicks and echoes made outside involving a pole, tree and parked car.
“When you played these sound files back to them later (inside the fMRI), they knew what it was that was out there when those echoes were being played back to them,” Goodale says.
The researchers also tested the pair’s ability to interpret each other’s clicks as they were played back to them in the scanner. “And they could,” he says.
When these sound files were played back to a person who doesn’t have the ability to echolocate, the brain doesn’t detect a difference. However, when Kish and Bushway hear the sound files, “you see this massive activation in his visual cortex,” Goodale says.
“It’s normally activated by light hitting the eye, but in his case, the presence of the echoes activates it.”
Even though the sound is being fed to Kish’s brain through his ears, the fMRI does not show any brain processing occurring in his auditory cortex when he is hearing the echoes.
“It obviously has to be processed by the auditory cortex, but somehow the echoes are differentially processed by the visual cortex,” Goodale notes. “He’s developed a special ability that makes use of this residual cortex.”
Kish, along with a few friends, has been invited to return to Western in June to study further the brain processes involved in learning the skill.
“Lore and I were blown away by his abilities,” Goodale says. “It shocked me how well he was able to echolocate.”
By studying Kish’s brain, Goodale thinks researchers will better understand how bats and dolphins are able to echolocate because he is able to vocalize his abilities. “There is a lot of information contained in echoes, but how it works we still don’t know everything,” Thaler adds.
Continuing research in this area will give researchers a better understanding of brain function, particularly how the senses are processed and what happens neurologically when one sense is lost.
Developing the ability to echolocate has provided Kish with an independence and freedom he otherwise wouldn’t have experienced. “The biggest barrier to blind people in general is not their blindness,” he says. “It is the imposition of a lack of freedom of both physical mobility and often social mobility.”
He continues, “The whole thing for us is that it can be taught. It is like learning the piano. Not everyone is destined to play at Carnegie Hall, but most people can learn to play.”
By participating in the study at Western, Kish hopes to validate his abilities, as well refine his teaching methods based on a better understanding of the neurological processes.
“We need more work like this; we need more science, more evidence behind it,” he says. “Among ophthalmologists, we find the most unhelpful thinking when it comes to blindness. To them, blindness seems to represent failure, the worst-case scenario.
“The support of the medical profession would really help move this kind of invaluable work forward. But, the medical profession needs to be jolted into pulling their heads out of their rigidly defined box, to understand that blindness isn't the end for everyone, but the beginning for many."
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