|Issue 15.04 - March 2007
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Paul Bach-y-Rita built his first "tactile display" in the 1960s. Inspired by the plasticity he saw in his father as the older man recovered from a stroke, Bach-y-Rita wanted to prove that the brain could assimilate disparate types of information. So he installed a 20-by-20 array of metal rods in the back of an old dentist chair. The ends of the rods were the pixels — people sitting in the chairs could identify, with great accuracy, "pictures" poked into their backs; they could, in effect, see the images with their sense of touch.
By the 1980s, Bach-y-Rita's team of neuroscientists — now located at the University of Wisconsin — were working on a much more sophisticated version of the chair. Bach-y-Rita died last November, but his lab and the company he cofounded, Wicab, are still using touch to carry new sensory information. Having long ago abandoned the vaguely Marathon Man like dentist chair, the team now uses a mouthpiece studded with 144 tiny electrodes. It's attached by ribbon cable to a pulse generator that induces electric current against the tongue. (As a sensing organ, the tongue has a lot going for it: nerves and touch receptors packed close together and bathed in a conducting liquid, saliva.)
So what kind of information could they pipe in? Mitch Tyler, one of Bach-y-Rita's closest research colleagues, literally stumbled upon the answer in 2000, when he got an inner ear infection. If you've had one of these (or a hangover), you know the feeling: Tyler's world was spinning. His semicircular canals — where the inner ear senses orientation in space — weren't working. "It was hell," he says. "I could stay upright only by fixating on distant objects." Struggling into work one day, he realized that the tongue display might be able to help.
The team attached an accelerometer to the pulse generator, which they programmed to produce a tiny square. Stay upright and you feel the square in the center of your tongue; move to the right or left and the square moves in that direction, too. In this setup, the accelerometer is the sensor and the combination of mouthpiece and tongue is the transducer, the doorway into the brain.
The researchers started testing the device on people with damaged inner ears. Not only did it restore their balance (presumably by giving them a data feed that was cleaner than the one coming from their semi circular canals) but the effects lasted even after they'd removed the mouthpiece — sometimes for hours or days.
The success of that balance therapy, now in clinical trials, led Wicab researchers to start thinking about other kinds of data they could pipe to the mouthpiece. During a long brainstorm session, they wondered whether the tongue could actually augment sight for the visually impaired. I tried the prototype; in a white-walled office strewn with spare electronics parts, Wicab neuroscientist Aimee Arnoldussen hung a plastic box the size of a brick around my neck and gave me the mouthpiece. "Some people hold it still, and some keep it moving like a lollipop," she said. "It's up to you."
Arnoldussen handed me a pair of blacked-out glasses with a tiny camera attached to the bridge. The camera was cabled to a laptop that would relay images to the mouthpiece. The look was pretty geeky, but the folks at the lab were used to it.
She turned it on. Nothing happened.
"Those buttons on the box?" she said. "They're like the volume controls for the image. You want to turn it up as high as you're comfortable."
I cranked up the voltage of the electric shocks to my tongue. It didn't feel bad, actually — like licking the leads on a really weak 9-volt battery. Arnoldussen handed me a long white foam cylinder and spun my chair toward a large black rectangle painted on the wall. "Move the foam against the black to see how it feels," she said.
I could see it. Feel it. Whatever — I could tell where the foam was. With Arnold ussen behind me carrying the laptop, I walked around the Wicab offices. I managed to avoid most walls and desks, scanning my head from side to side slowly to give myself a wider field of view, like radar. Thinking back on it, I don't remember the feeling of the electrodes on my tongue at all during my walkabout. What I remember are pictures: high-contrast images of cubicle walls and office doors, as though I'd seen them with my eyes. Tyler's group hasn't done the brain imaging studies to figure out why this is so — they don't know whether my visual cortex was processing the information from my tongue or whether some other region was doing the work.
I later tried another version of the technology meant for divers. It displayed a set of directional glyphs on my tongue intended to tell them which way to swim. A flashing triangle on the right would mean "turn right," vertical bars moving right says "float right but keep going straight," and so on. At the University of Wisconsin lab, Tyler set me up with the prototype, a joystick, and a computer screen depicting a rudimentary maze. After a minute of bumping against the virtual walls, I asked Tyler to hide the maze window, closed my eyes, and successfully navigated two courses in 15 minutes. It was like I had something in my head magically telling me which way to go.
In the 1970s, the story goes, a Navy flight surgeon named Angus Rupert went skydiving nude. And on his way down, in (very) free fall, he realized that with his eyes closed, the only way he could tell he was plummeting toward earth was from the feel of the wind against his skin (well, that and the flopping). He couldn't sense gravity at all.
The experience gave Rupert the idea for the Tactical Situational Awareness System, a suitably macho name for a vest loaded with vibration elements, much like the feelSpace belt. But the TSAS doesn't tell you which way is north; it tells you which way is down.
In an airplane, the human proprioceptive system gets easily confused. A 1-g turn could set the plane perpendicular to the ground but still feel like straight and level flight. On a clear day, visual cues let the pilot's brain correct for errors. But in the dark, a pilot who misreads the plane's instruments can end up in a death spiral. Between 1990 and 2004, 11 percent of US Air Force crashes — and almost a quarter of crashes at night — resulted from spatial disorientation.
TSAS technology might fix that problem. At the University of Iowa's Operator Performance Laboratory, actually a hangar at a little airfield in Iowa City, director Tom Schnell showed me the next-generation garment, the Spatial Orientation Enhancement System.