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The Science of the Loving Touch

Researchers say certain nerves are designed to transmit pleasure from touching

FRIDAY, Aug. 2, 2002 (HealthDayNews) -- How do you feel when you're involved in a soft and slow caress? Does this kind of sensation thrill you more than touching a frying pan or a doorknob?

Researchers think they may have the reason why: Some nerves in the human body appear to be designed to specifically detect pleasurable sensations on the skin.

Scientists in Sweden found that a woman who had lost most of her sense of touch could still feel pleasure when someone stroked her skin with a soft paintbrush.

"This is an important first step in teasing out the complex anatomy that must govern the emotional aspects of our sense of touch," said Dr. James Grisolia, a neurologist at Scripps Mercy Hospital in San Diego.

While it may not get quite the amount of news coverage as each of its four sister senses, touch still attracts plenty of attention from scientists, some of whom are intrigued by its emotional aspects. Researchers have learned, for instance, that baby monkeys and humans need to be touched by their mothers in order to function properly.

"Everyone already knows that touch can convey many emotional messages -- threat, comfort, sexual urge, nurturing, etc. -- so there must be many powerful connections between sensory and emotional systems," Grisolia said. "But they are poorly understood.

Researchers do know that touch sensations travel to the brain at fast or slower speeds along different types of nerve fibers.

The Swedish researchers examined a woman who had lost the use of one type of "fast" nerve fibers, known as A fibers. These fibers transmit the fine details of touch, said study co-author Dr. Hakan Olausson, a neurophysiologist at Sahlgrenska University Hospital in Gothenberg.

The woman lost much of her sense of touch about 25 years ago after suffering from an inflammatory nerve disease, Olausson said. In order to live, she has to rely on sight instead of touch.

But the disease spared the woman's so-called C fibers, which transmit the sensations from light touch.

Researchers stroked her skin with a paintbrush and watched what happened. They report their results in the September 2002 issue of Nature Neuroscience.

The woman was able to feel a sense of pleasure, Olausson said, suggesting that the C fibers transmit that type of sensation and are especially sensitive to the feeling of slow stroking of the skin.

The next step is to test their theory about the C fibers by challenging it from the opposite direction, Olausson said. He wants to work patients whose C fibers don't function.

"If our hypothesis is right, these patients should feel less pleasure when being stroked on affected skin areas compared to unaffected skin areas," Olausson said.

As research in this area progresses, doctors may develop better ways to treat and rehabilitate stroke sufferers, Grisolia said.

It may even be possible to figure out "what goes wrong" in people who grow up deprived of a mother's touch, he said.

What To Do

Learn about different types of touch from Oregon State University.

Scientists now know that our emotions originate in the brain. For an original view of that, the National Institute of Mental Health offers Seeing Our Feelings.

SOURCES: James Grisolia, neurologist, M.D., Scripps Mercy Hospital, San Diego; Hakan Olausson, M.D., Ph.D., neurophysiologist, Sahlgrenska University Hospital, Gothenberg, Sweden; September 2002 Nature Neuroscience
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