Tongue may be portal to brain for devices
By Charles Choi
UPI Science News

MADISON, Wis., Feb 28 (UPI) -- Quadriplegics might one day feel the hand of a loved one through a device that speaks to the brain via the tongue.

A new device developed by scientists at the University of Wisconsin in Madison uses tiny electrical impulses to route sensory information through the tongue to the brain. The device was initially funded by the U.S. military to guide Navy Seals through dark waters, but lead researcher Paul Bach-y-Rita said the invention could have any number of applications -- from giving navigational cues for the blind to assisting firefighters as they comb through the confusion of smoke-filled buildings.

"I think one of the major uses will be telecommunications and entertainment, actually," Bach-y-Rita said. "You could add sensation to the Internet."

The researchers have recently applied for a patent for the device, called the Tongue Display Unit. It currently looks like a tongue depressor hooked up by a flexible ribbon to a small box of electronics. But the scientists say a grant from the National Institutes of Health should allow them to develop miniaturized electronics that can make the device as small or smaller than a dental retainer.

The Tongue Display Unit is made up on a tiny array of 144 copper electrodes plated with gold. "The gold is there for biocompatibility," explained researcher Kurt Kaczmarek. "When you normally pass an electrical current through copper in the mouth, it stains the tongue green."

Through the coordinated firing of low-current, microsecond-long electrical bursts 200 times per second, the device routes information from a camera, computer or other device straight to the brain.

"It feels like a tingling vibration," Kaczmarek said. "It's a very subjective thing -- some people have said it's like soda bubbles, while others say it's like an arm falling asleep. It's a bit unusual, but it's a very safe thing. I let my two kids at home play with it. They call it 'the tongue tickler.'"

"After a while, the subjects said impulses didn't feel like anything at all, unless they were specifically asked," Bach-y-Rita added.

The device is based on decades of research that used electrodes to deliver sensory information through the skin to the brain. In principle, electrode interfaces act very much like canes do for blind people, Bach-y-Rita explained.

"Even though all the information is going through the receptors in the hand, after a while it's felt in the brain," he said. "The brain is very malleable."

Interfaces on the forehead have helped lepers experience sensation from their fingers, while blind children using fingertip interfaces hooked up to cameras have identified geometric figures. In the past, however, these interfaces were largely ignored because they needed creams to increase electrical conductivity across the skin and bulky, noisy, power-hungry electronic equipment.

"Who wants to look like a Martian?" Bach-y-Rita commented. The research team has found that the mouth has proven an ideal surface to hide all the electrodes, because it's loaded with nerves and bathed in electrically conductive saliva. Furthermore, the tongue requires only 3 percent of the voltage the fingertip does for stimulation.

To avoid cables connected to cameras and computers from going into people's mouths, the researchers plan on using short-range radio-frequency transmitters that wirelessly broadcast signals across the cheek.

After 10 hours of training, the researchers found that there was "crossover" -- volunteers felt sensations delivered in their minds instead of in their mouths. With at least 100 hours training, subjects could execute complex tasks such as hitting a ball they could not see that was rolling down a ramp.

The researchers are currently working conceptually on devices about the size of a retainer that could help people who have lost their sense of balance. The devices have tiny pitch-and-roll sensors pasted onto them that were originally placed inside artillery shells in order to evaluate their trajectories. The scientists said the next stage of that research will be to help pilots with spatial disorientation, particularly in the dark.

"The device would give you valuable information to tell which way is up, which is important when you're not headed up," Bach-y-Rita said.

Other possible applications include:

• A surgical technique called sensate cardiac robotics, in which heart surgeons using a robotic arm could actually feel what they were doing.
  
  
• Sensate robotic hands, in which quadriplegics could feel objects they pick up or hold. The sensory device itself might even help people with injured spinal cords regain feeling during sexual intercourse.
  
  
• Navigation for the blind. The scientists said colleagues in France have received a $1 million grant to help guide blind babies using the technology.
  
  
• A third sense in the video gaming industry, allowing players to feel things as well as see and hear them.
  

The scientists emphasized, however, that the balance-aiding device is in the early stages of conceptual design right now and at least two years away. Any other applications may be even farther down the line.

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