In the near future, blind people might get around by following electric currents caused by a device fitted in their mouths.
If so, it's all because two scientists during the course of an experiment licked an electrode array -- and realized that the tongue was one of the greatest messengers to the brain.
The Tongue Display Unit is being developed by Paul Bach-y-Rita and Kurt Kaczmarek at the University of Wisconsin.
The concept of sensory substitution -- for example, honing the sense of touch to receive information that would normally be processed by the sense of vision -- is not new.
"It's part of a train of research that has been going back decades. The concepts have been there, but instrumentation has been a problem," Kaczmarek said.
Kaczmarek's research team is trying to solve the problem by creating a "tactile tongue-based, electrical impulse matrix sensor." It looks like a tongue depressor, with 144 gold-plated electrodes covering a stamp-sized area.
Information from a computer or a video camera is transported through low-current, electrical bursts on the tongue -- which in turn send these messages to the brain.
"It works the same way as blind people use their fingertips to read Braille," Kaczmarek added.
Kaczmarek said that the part of the brain responsible for processing touch information from the tongue is quite large and similar to the part that receives messages from the fingertips -- thus making the tongue the ideal envoy.
Another advantage is that the tongue is teeming with sensory neurons that are covered in electrically conductive saliva, and it requires only 3 percent of the voltage needed for fingertip stimulation.
People who tested the device said the electric stimulus feels tingly, like soda bubbles. The sensation does not cause discomfort but does tend to leave a metallic taste in the mouth. Kaczmarek said he has not heard anyone complain of tissue irritation.
When fully developed, the tongue stimulator will fit into a small mouthpiece, like a dental retainer, that receives information from a miniature TV camera, microelectronics and an FM transmitter built into a pair of glasses.
"It is possible but it is an engineering challenge," Kaczmarek said. "It will also take millions of dollars, and we have made applications for grants."
Eliana Sampaio, Kaczmarek's colleague at the Louis Pasteur University in Strasbourg, France, is trying to make the technology work for blind infants.
"She is still in the initial stages of her research," said Kaczmarek. "But the idea is to let the babies experience spatial concepts they would otherwise not have access to."
"I don't know exactly what is being done -- maybe they will wrap one of these electrodes around a pacifier -- and attach the camera to the big toe."
The scientists are trying to look for different uses for the technology.
"If we could get into the computer gaming area, it would be a potentially huge market," Kaczmarek said.
"We are looking (at) the stimulus as a secondary form of feedback. People are already using force-reflecting joysticks. Since one can get tactile information with this device, you would be able to feel the contours of objects that you are interacting with on the screen," he added.
