Mind & Brain / Senses

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."

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."