May 25, 2011 at 5:00 PM ET
Daniel Kish is blind. But he navigates the world by issuing a stream of clicks from his mouth and then listening as the sound of the clicks echoes off buildings, objects, even landscaping to create a mental map in his head. In other words, Kish uses echolocation, much like a dolphin, or a bat.
Blind since the age of 13 months, when retinoblastoma forced doctors to remove his eyes, Kish, a 43-year-old psychologist living in Long Beach, Calif., has become a minor celebrity via You Tube and TV news reports showing him riding a bike and performing other feats considered impossible for a blind man.
Now researchers at the University of Western Ontario think they’ve partly figured out how his brain has created a work-around for his blindness. In the journal PLoS One, the researchers, led by Lore Thaler in the school’s department of psychology, report that as far as Kish’s brain is concerned, he really is “seeing” the world.
Thaler and colleagues recorded Kish and another blind echolocator outdoors. Both men could distinguish a flag pole, a tree, a car and a building. When tested inside a special non-echoing chamber that eliminates any unintentional sound, the blind men were able to sense the location of a pole within a few degrees and its angle of lean. They were able to distinguish a concave surface (actually a construction worker’s hard hat turned so the inside faced them) from a flat surface (a cube), and moving versus stationary objects.
Then Thaler played recordings of these tests while the men’s brains were imaged with a functional magnetic resonance imaging (fMRI) machine to map which brain regions were activated when the men heard echoes.
Surprisingly, their auditory cortices were no more active when they heard echoes than when they heard echo-less ambient sounds. But once they heard echoes, the calcarine cortex, otherwise known as the visual cortex, lit up. Two sighted male control subjects showed no increase in visual cortex activity when exposed to echoes.
According to Thaler, “at this point the reason for the [unique] brain activity is unknown. We have to investigate this in future studies.”
Kish speculates that echoes are like individual words with minute differences between the echo from a brick wall, or a tree, or a hard hat. Each “word” is first processed in the brain’s auditory system and then sent to the visual cortex to create a corresponding image.
Whatever the mechanism, Kish thinks the revelation could be a boon to the blind. He has traveled the world as president of World Access for the Blind training other blind people to use echolocation. But the system has never been scientifically validated, leading to concerns that Kish was unique or that echolocation was a kind of trick. With this study, Kish said, “maybe we can assist the brain in its imaging. Maybe we can create better training. And with hard science maybe we can get more funding.”
It’s possible we all have latent echolocation ability. Rodents use a system of high pitched sounds to help them “see” the world and Thaler believes that “we probably all could learn to do it, some much better than others.”