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, seen in the photograph on the opposite page, 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?