Scientists are tickling giggly rats to crack the mysteries of laughter (link)
At parties and bars, he introduces himself as a "rat tickler."
The title makes Shimpei Ishiyama sound like he belongs in some forgotten guild of yore, with the Victorian "pure-finders," who collected dog dung for a living, and the "flankers and flaggers," who kept partridges in the range of hunters' guns.
But he is, in actual fact, a neuroscientist, and his rat-tickling is anything but antiquated. By trying to titillate these rodents — and recording how their neurons respond — Ishiyama and his adviser are unraveling a mystery that has puzzled thinkers ever since Aristotle posited that humans, given their thin skin and unique ability to laugh, were the only ticklish animals.
Aristotle was wrong, it turns out. In a study published Thursday in Science, Ishiyama and his adviser, Michael Brecht, not only found that rats squeaked and jumped with pleasure when tickled on their backs and bellies, but also that these signs of joy changed according to the rodents' moods. And, for the first time, they pinpointed a cluster of neurons that makes this sensation so powerful that it causes an individual being tickled to lose control.
"It's truly innovative and groundbreaking," said Jeffrey Burgdorf, a neuroscientist at Northwestern University who reviewed the paper. "It takes the study of emotion to a new level."article continues....