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Researchers Find Way to Enhance Touch Sensitivity - 2003-07-03

The sense of touch is crucial to almost everything we do, from buttoning a shirt to using a keyboard. But some people lose sensitivity in their fingers, making it difficult to carry out routine tasks. Now, German researchers say they have come up with a way to enhance fingertip sensitivity.

The sense of touch guides us through a maze of everyday activities, from dressing ourselves to preventing burn injuries. But we lose touch sensitivity as we age and it is deadened in some people who have suffered a stroke.

German researchers have found they can improve touch sensitivity by turning on molecules, known as NMDA receptors, in the brain.

In a paper published in the journal Science, the researchers describe a combination therapy in which they applied a mild electrical current for three hours to the index fingers of more than two dozen elderly, healthy volunteers and gave them a drug.

Some of the volunteers received a stimulant known as an amphetamine that increased the activity of the NMDA receptors. And to prove that they could switch on and off the receptors, researchers gave other volunteers a compound that blocks NMDA, which made their fingers less sensitive.

Scientists then measured touch sensitivity in the volunteers with pins.

Lead author Hubert Dinse of Ruhr University in Bochum, Germany says the experiment temporarily doubled finger sensitivity in the group that got the amphetamine.

"With this protocol, we were able to bring the acuity of an 80-year-old subject to that of a 50-year-old, which is quite a remarkable achievement," he said.

Mr. Dinse says the combination of electrical stimulation and amphetamines appears to reorganize parts of the brain associated with touch in a positive way.

"There will be ways that right now sound like science fiction or once thought it would not be possible [to affect touch]," he said. "But it is very clear that such techniques like [a] combination of electrical stimulation with drugs will be very, very effective."

But the study volunteers lost their improved finger acuity one to two days after the combination therapy was stopped. The challenge now for researchers is to find a way to make the improvement permanent.