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Can You See With Your Tongue?

The brain is so adaptable, some researchers now think, that any of the five senses can be rewired.

By Michael Abrams and Dan Winters
Jun 1, 2003 5:00 AMApr 11, 2023 4:08 PM


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I'm sitting at a table draped in black, surrounded by black curtains. Candles, spheres, and unfamiliar symbols have been placed before me. My right hand, arms, and head are strapped with wires, and my mouth is filled with electrodes. I'm blindfolded.

Although this may sound like a scene for a Black Mass, it's even stranger than that: I'm trying to see with my tongue.

The gear I'm wearing was invented by Paul Bach-y-Rita, a neuroscientist at the University of Wisconsin at Madison. Bach-y-Rita has devoted much of his career to a single, revolutionary concept: that our senses are interchangeable. The brain, Bach-y-Rita and many other neuroscientists believe, is an organ of astonishing plasticity: If one part of it is damaged, another part can serve the same function. To prove the point, his collaborator Kathi Kamm, a professor of occupational therapy at the university's Milwaukee campus, has strapped a small video camera to my forehead and connected it to a long plastic strip hanging from my mouth. A laptop computer reduces the camera's image to 144 pixels. Those pixels are converted to an electric current that is sent to the business end of the plastic strip — a 12-by-12 grid of electrodes that rests on my tongue.

Kamm sits down in front of me. She says she's holding a ball, but I can't hear a sound as she rolls it back and forth over the cloth-covered table. She says the ball will soon be rolling toward me — to my left, my right, or straight at me — but my eyes and ears have no way to tell where it's going.

That leaves my tongue. It has more tactile nerve endings than any part of the body other than the lips. What the camera sees is zapped onto my tongue's wet, conductive surface. As Kamm rolls the ball, my blindfolded eyes see nothing, but a tingling passes over my tongue. When she sends the ball my way, my hand leaps out to the left.

I've caught it.

Paul Bach-y-Rita says he owes his unorthodox thinking to life with his father. In any argument over the dinner table, Pedro Bach-y-Rita "would always take the opposite side of the one he thought I would think."

"We don't see with our eyes," Bach-y-Rita is fond of saying. "we see with our brains." The ears, eyes, nose, tongue, and skin are just inputs that provide information. When the brain processes this data, we experience the five senses, but where the data come from may not be so important. "Clearly, there are connections to certain parts of the brain, but you can modify that," Bach-y-Rita says. "You can do so much more with a sensory organ than what Mother Nature does with it."

Bach-y-Rita, who is 69, looks like a cross between Albert Einstein and Harpo Marx. His hair springs from his head in a wild gray Afro, and his face often bears a comic, knowing smirk. He owes his iconoclastic spirit to his late father, he says. A professor of Spanish at the City University of New York, with a passion for 16th-century Catalonian poetry, Pedro Bach-y-Rita nearly destroyed his career in 1947 by organizing the country's first civil-rights strike at a university. He encouraged his children to be equally rebellious. Rather than raise Paul as a Catholic like himself or Jewish like his wife, for instance, he urged him to choose his own religion. Paul chose to become a Swedish Lutheran — he liked the pastor at Bernadotte Lutheran Church in the Bronx. But when he later won a scholarship to a Lutheran college, he turned it down. He didn't feel right accepting the money, he explained, since he was not a believer.

In 1958, at the age of 65, Pedro Bach-y-Rita suffered a stroke that left him confined to a wheelchair, hardly able to move or speak. Paul's brother, George, was a medical student at the University of Mexico at the time. Rather than let his father vegetate in a nursing home, George brought him to his house and put him to work. "It was tough love," Paul says. "He'd throw something on the floor and say 'Dad, go get it.'" The neighbors would watch in dismay as the old man struggled to sweep the porch. "But for him, it was so rewarding," Paul says. "This useless man was doing something."

Neurologists in those years believed that brain damage was impossible to reverse. If a stroke caused memory loss, paralysis, or dementia for more than a few weeks, the condition was permanent. Nevertheless, after three years Paul's father recovered completely. He went back to teaching and worked for another five years. When he died in 1969 at the age of 73, it was from a heart attack while hiking at an altitude of 9,000 feet in the mountains of Colombia.

The neuropathologist who autopsied Pedro's brain later published a paper on the case in the American Journal of Physical Medicine, complete with pictures of Pedro's devastated brain. "It was shocking," Paul says. "My father had recovered so much that we'd figured he didn't have much brain damage." Why did he recover, Paul remembers thinking, when everyone else said he couldn't?

Reteaching the Brain to Balance

The sense of balance may be the simplest of the senses and therefore the easiest to redirect in the brain. It stems from tiny hair cells in the inner ear that are surrounded by a layer of gel. When you move your head, the gel is pushed against the hair cells, which relay the information to the brain. The whole system is called the vestibular sense.

Over the past 40 years or so, several thousand people in the United States have lost this sense, due to an antibiotic called gentamicin. One of the drug's side effects is ototoxicity: It can kill the hair cells in the inner ear. Cheryl Schiltz lives in Windsor, Wisconsin. In November 1997, after taking gentamicin for 17 days, she woke up and couldn't stand."I had to crawl," she says. "It was like being extremely intoxicated. I was scared to death."

Schiltz also suffers from tinnitus, short-term memory loss, and vision problems. "It's a living hell," she says. She eventually found solace among other victims of gentamicin, who call themselves The Wobblers, but real relief came only after her physician referred her to Paul Bach-y-Rita.

Schiltz was dubious at first. "He explained it to me, and I'm going, 'the tongue?' I thought he was kidding." Nevertheless, she let Bach-y-Rita outfit her with a hard hat and a strip of electrodes for her tongue. The hat contained an accelerometer that registered Schiltz's movements and relayed the information to a circle on the grid in her mouth. If she leaned forward, the circle moved forward too. All Schiltz had to do, to stay balanced, was keep the circle centered on her tongue.

The results were almost instantaneous. "All of a sudden, I started crying," Schiltz says. "I had forgotten what it was like to see clearly, what it was like not to stagger. It was like the hand of God coming down and touching me." Within half an hour she was standing without assistance. "I was shocked," Bach-y-Rita says. "She learned it almost immediately. I think the reason is that she already had partially trained herself to understand tactile cues. She's been using the contact of her feet on the ground."

Schiltz later took the experiment even further. After 20 minutes spent centering the circle, she took off the hat, pulled out the electrodes, and kept her balance for a full hour without any apparatus. "I ran through the building in my socks," she says. "I danced with Paul and climbed up and down chairs and tables. I felt cured, literally cured." — M.A.

Paul's career changed course after Pedro's death. He quit the job he had taken after medical school, at the Smith-Kettlewell Institute of Visual Sciences in San Francisco, and took a residency at Stanford's Santa Clara Valley Medical Center. "It was quite stupid or brave or something to drop out and go into residency," Bach-y-Rita says. But he wanted to study people like his father — to re-create the miracle he had witnessed.

After settling down as professor of rehabilitation medicine at the University of Wisconsin, Bach-y-Rita turned his attention back to the senses. He knew that victims of leprosy, for instance, can lose the sense of touch in their limbs, so he developed a glove with transducers on each fingertip that were connected to five points on the forehead. When his test subjects touched something with the gloves, they felt an equivalent pressure on their heads. Within minutes they were able to sense the difference between rough and smooth surfaces — and they quickly forgot that their foreheads were doing the feeling.

If sight and touch can swap paths to consciousness, Bach-y-Rita reasoned, so can sound. In the 1980s, his team plugged a microphone into a vibrating belt. Low frequencies picked up by the mike tickled the left side of the waist; high frequencies tickled the right. Deaf people who donned the belt claimed it helped them read lips.

Impressive as they were, Bach-y-Rita's experiments did not impress mainstream neuroscientists. As early as 1969, he published a paper in Nature on one of his devices, but his mentor, the Nobel Prize-winning neurophysiologist Ragnar Granit, couldn't understand what he was up to. "He called me into his parlor and said 'Paul, you know how I appreciate your work on eye muscles. But why are you wasting your time on this adult toy?'"

The skepticism was understandable. In those early years, and to a lesser degree today, many neuroscientists believed that the brain is compartmentalized — that visual information, for instance, goes straight from the eye to the visual cortex through a fixed network of nerves. If any part of the system is damaged, sight is impossible. Only the eyes can see.

This notion dates back to 1861, when the pioneering French neurologist Paul Broca found lesions in the frontal lobe of a speechless man. Broca concluded that certain parts of the brain are responsible for certain tasks, and a deluge of later research seemed to prove him right. Most recently, functional MRI and PET scans have shown that different areas of the brain light up depending on whether a person is identifying colors, recognizing faces, registering emotions, or learning a language.

Bach-y-Rita says that's only part of the story: "In any given field there's a conceptual substance — I love that phrase — a general understanding that's not easily changed." In trying to understand the brain, for instance, neuroscientists have focused on synapses — the junctions between nerve-cell endings — as the essential transmitters of thought and feeling. Children both grow and prune back synaptic connections at a furious rate as they develop, but the process all but stops in adulthood. Many researchers still believe, therefore, that a damaged brain causes permanent deficits.

"The synapse is a concept in evolution; it's what's observable under a microscope," Bach-y-Rita says. "There are other things going on between cells." Only 10 percent of the cells in the brain are neurons, he says. They make up the brain's hard wiring and send messages with electrical pulses. The rest are glial cells whose precise function is not well understood. Neurons release neurotransmitters that are taken up by specific receptors, but many glial cells receive and emit neurotransmitters that float through the brain as free agents. Some glial cells congregate near lesions, for instance, and in areas of the brain where learning is going on. "It's so much less cumbersome to have changes in this system than it is in the whole wiring system," Bach-y-Rita says. Much of the human intellect, he believes, may come from these nonelectrical, free-floating signals. How else can our brains achieve so much mind power without using any more energy, pound for pound, than the brains of other animals?

Whether or not Bach-y-Rita is right about glial cells, more and more evidence suggests that the senses can be redirected. At Harvard University in the late 1990s, for instance, neurologist Alvaro Pascual-Leone performed brain scans of blind subjects. When he asked them to read braille with their reading fingers, their visual cortex lit up. When sighted people performed the same task, their visual cortex stayed dormant. More recently, neuroscientist Mriganka Sur at MIT took young ferrets and connected fibers coming from their retinas to their auditory pathway. They grew up with perfect vision.

Thanks to such studies, the term "plasticity," once taboo in neuroscience papers, has become fashionable. "At any meeting you see loads and loads of papers on plasticity," Bach-y-Rita says. Still, even some of his allies think he claims too much. Sight is a rich and complicated phenomenon, they say, and the eye such an astonishing organ, that it can never be replaced. Michael Merzenich, a neuroscientist at the University of California at San Francisco, has been a leading proponent of brain plasticity for two decades. Bach-y-Rita's tongue device demonstrates "a powerful substitution," he says, but he doubts that it could provide anything like actual sight. "If it's not stimulating the retina, it's unlikely, to my mind, that it's seeing."

"I totally disagree," Bach-y-Rita says. "There's nothing special about the optic nerve. The brain doesn't care where the information comes from. Do you need visual input to see? Hell, no. If you respond to light and you perceive, then it's sight."

Cheryl Schiltz lost her sense of balance after taking an antibiotic. Then she tried Bach-y-Rita's tongue gear. An accelero-meter in her hat transmits data on her movements to a receptor on her tongue. By keeping the tingling centered, Schiltz can stand and walk again. The first time she tried it, she started to sob: "My God, I feel normal."

Bach-y-Rita sounds convincing, but in the lab I'm still left wondering what exactly I'm experiencing. The images have a sour, battery taste and feel like the pelting of a hot summer cloudburst. They certainly convey some sense of where things are around me, but is that the same as sight?

In practical terms, the answer may be irrelevant. When Kamm places a small white cube somewhere on the table, I can reach out and grab it nine times out of 10, even though I'm blindfolded. I can even recognize large letters, as long as I can bob my head around to get a better sense of their outlines. Given a few more hours with the device, I might eventually learn to forget the tingling in my mouth and just see. Is that sight?

The question might best be asked of one of Kamm's subjects, a 16-year-old named Beth with a gift for music. Beth is the top singer in her high school choir and hopes to study music in college and become a composer. She has also been blind since birth. Until she met Bach-y-Rita, she never knew how a conductor gestures to keep time, but by wearing the electrodes, she learned the gestures in half an hour. If she eventually learns to "see" these movements across a room, and to understand their meaning, is it useful to call this anything other than sight?

Perhaps it is, in which case Bach-y-Rita's research is teaching us something even more interesting — that sight is not just a detailed understanding of the light and space around us; it's a particular, even arbitrary, feeling.

To Bach-y-Rita and his clients, though, the difference isn't all that important. The Navy SEALs are working with him on a system that will allow them to see infrared through their tongues and to find their way through murky waters, leaving their eyes free for other tasks. NASA has worked with him to develop sensors to enable astronauts to feel things on the outside of their space suits. And the Institute for Human and Machine Cognition in Pensacola, Florida, is using his ideas to build vests that will tickle pilots to alert them to other planes or incoming missiles.

Last October Bach-y-Rita received the Coulter Award from the American Congress of Rehabilitation Medicine in recognition of his contributions to the field of neurorehabilitation. After decades of struggling at the fringes of his discipline, he now has the financial backing to bring his work into the mainstream. Within the next couple of years, he hopes to create a miniature version of his tongue-vision system that will fit into a wireless retainer. A tiny camera in a pair of glasses will send the image via radio waves into the mouth. If the device works, not only will the blind see better, but the rest of us may have access to senses we've never even dreamed of. "Anything that can be measured can be transported to the brain," Bach-y-Rita says. "We can get it to the brain, and the brain can learn how to use it."

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