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October 23, 2018

Seeing with Your Tongue

Erik Weihenmayer is the only blind person to have climbed Mt. Everest. He was born with juvenile retinoschisis, an inherited condition that caused his retinas to disintegrate completely. He took to climbing after being introduced to it at a summer camp for the blind. He learned to pat the rock face with his hands or tap it with an ice axe to find his next hold, following the sound of a small bell worn by a guide, who also described the terrain ahead. With this technique, he has summited the tallest peaks on all seven continents. 10 years ago, Weihenmayer started using BrainPort, a device that enables him to “see” the rock face using his tongue. The BrainPort consists of two parts: a band on your forehead supports a tiny video camera; connected to this by a cable is a postage-stamp-size white plastic lollipop, which is held in the mouth. The camera feed is reduced in resolution to a grid of four hundred gray-scale pixels, transmitted to his tongue via a corresponding grid of four hundred tiny electrodes on the lollipop. Dark pixels provide a strong shock; lighter pixels merely tingle. The resulting vision is a sensation that Weihenmayer describes as “pictures being painted with tiny bubbles.” Without the BrainPort, Weihenmayer’s climbing style is inelegant but astonishingly fast—a spidery scramble with arms and feet sweeping like windshield wipers across the wall in front of him in order to feel out the next hold. With the device on his tongue, he is much slower, but more deliberate. After each move, he leans away from the wall, surveys the cliff face, and then carefully reaches his hand out into midair, where it hovers for a split second before lunging toward a hold several feet away. Weihenmayer told me that he wouldn’t take the BrainPort up Everest—relying on fallible electronics in such extreme conditions would be foolhardy. The BrainPort, which uses the sense of touch as a substitute for sight, is one of a growing number of so-called sensory-substitution devices. As the BrainPort’s inventor, the neuroscientist Paul Bach-y-Rita, put it, “You don’t see with the eyes. You see with the brain.” Bach-y-Rita, who died in 2006, is known as “the father of sensory substitution,” although, as he liked to point out, both Braille and white canes are essentially sensory-substitution systems, replacing information that is typically visual—words on a page, objects at a distance—with tactile sensation. He even argued that writing ought to be considered the original precursor, because it enabled the previously auditory experience of the spoken word to be presented visually. Bach-y-Rita began his medical career in visual rehabilitation, gaining a reputation as a specialist in the neurophysiology of eye muscles. In 1959, his father, Pedro Bach-y-Rita, a Catalan poet who had immigrated to the Bronx and taught at City College, suffered a catastrophic stroke. Doctors said that he would never speak or walk again, but Paul’s brother, then a medical student, designed a gruelling rehabilitation regimen: Pedro had to crawl around on kneepads until he could walk, and to practice scooping up coins until he had learned to feed himself. After a year, Pedro went back to work as a teacher and, after two, he was able to live independently. When he eventually died—in 1965, of a heart attack—he was hiking up a mountain in Colombia. And yet, as his autopsy revealed, his brain was still severely damaged; the areas responsible for motion and involuntary muscle movements had been all but destroyed. “How could he have recovered so much?” Bach-y-Rita marvelled. “If he could recover, why didn’t others recover?”
Posted by RBME Team