Wired's Sunny Bains turned in an excellent piece on technology-induced synaesthesia -- the use of technological prostheses to give humans new senses, or to cross-wire existing ones. Some of the examples she cites are really compelling, like the researcher who surrounded his midriff with rumble-packs, the northernmost of which would gently vibrate, so that he could "feel" north at all times. Eventually, he ended up with a faultless sense of direction, able to pilot himself around strange cities without getting lost. Even more compelling was the rewiring of a subject's sense of balance: University of Wisconsin installed a feedback mechanism on the tongues of subjects with severe balance problems caused by inner-ear disruption. Although their inner ears told them they were whirling around, their tongues vibrated on the left if they were leaning to the left, on the right if they were leaning to the right, and in the middle if they were upright. The subjects were able to overcome their inner ear's faulty directions and navigate without falling over.
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.