Learning to see with your tongue
Most of us see with our eyes, but what if we could see with other parts of our body, too? The idea may seem ridiculous, but it's already been done. Nearly a half-century ago, maverick neuroscientist Paul Bach-y-Rita discovered that it was possible to "rewire" the adult brain, connecting regions in ways no one ever had imagined. Today, his ideas have given a handful of blind people the ability to see for the first time—using their tongues.
For a long time, scientists believed that after childhood, the brain became "fixed" in its ways and impossible to change. But Bach-y-Rita reasoned that because the nerves carrying messages from one part of the body to the brain are identical to those carrying messages from other body parts, it might actually be possible, even in adulthood, to substitute one sense for another.
So Bach-y-Rita went to work.
First he developed a device that translated images caught on camera into pulses that were transmitted onto a blind person's back. By figuring out what image was being "drawn" onto their backs, people could, in a sense, see the image that was in front of them.
Bach-y-Rita then shifted his medium from the back to the tongue, which is both covered in nerves and highly conductive. He developed a device called the BrainPort consisting of 625 sensors that deliver fine-grained spatial information to the tongue and, by extension, the brain. Over time, blind people using the device truly start "seeing": When the tongue is tapped, the regions of the brain associated with vision light up in response.
The BrainPort does, in effect, rewire the brain.
(video available via the above link)