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Brain hampers self-tickling, study says NEW YORK (October 19, 1998 5:03 p.m. EDT http://www.nandotimes.com) -- Why is it so hard to tickle yourself? Because one part of the brain tells another: "It's just you. Don't get excited," say researchers who watched the brains of people trying to tickle themselves. The killjoy is the cerebellum, found in the lower back of the brain, the researchers suggest. The brain is already known to predict what a person will feel when his or her body does something. That way, it can ignore expected sensations like pressure on the soles of the feet while walking, and save its attention for more important things, like the feeling of a foot bumping a stone. Prior studies implicated the cerebellum in telling the brain what to expect from the body's own movements. The study on self-tickling was reported in the November issue of the journal Nature Neuroscience by researchers including Ph.D. student Sarah-Jayne Blakemore at University College London. "I think it's a wonderful step forward" in understanding how the body monitors its actions, said Deborah Yurgelun-Todd, director of the cognitive neuroimaging laboratory at McLean Hospital in Belmont, Mass. But it's too soon to say whether the cerebellum is the only brain region involved in dampening the tickle sensation, she said. Some other brain scientists were skeptical of the finding. Allan Smith of the University of Montreal said his monkey studies disagree with the new research on how the cerebellum reacts to a touch on the hand. For the new study, six volunteers lay on their backs in a brain-scanning machine with their eyes closed. Nearby was a device with a piece of soft foam attached to a plastic rod. When the rod moved up and down, it tickled the volunteers' left palms with the foam. With the brain scanner running, the volunteers and an experimenter took turns moving the rod, so the volunteers were either tickling themselves or being tickled. On some occasions, the foam was secretly removed so that the volunteers would move the rod with their right hands but feel nothing on their left hands. The researchers compared activity in different parts of the brain during the various experimental situations. The results suggest that during self- tickling, the cerebellum tells an area called the somatosensory cortex what sensation to expect, and that this dampens the tickling sensation, they said. By Malcolm Ritter, AP Science Writer Copyright 1998 Nando.net Copyright 1998 The Associated Press janet paterson - 51/10 - almonte/ontario/canada http://www.newcountry.nu/pd/members/janet/ [log in to unmask]