A rare condition may help researchers understand the origins of laugher in the brain, a new study says.
The study involved patients with gelastic epilepsy, an uncommon condition characterized by seizures that manifest as uncontrollable laughing spells. Researchers knew patients with this condition have lesions in an area of the brain called the hypothalamus. The new study pinpointed these lesions in a specific region in the back of the hypothalamus.
By honing in on a precise region, the researchers said they hope to get a better idea of what parts of the brain are involved in laughing, which may be possible to ascertain by looking at the parts of the brain that are connected to this specific region of the hypothalamus.
"It's almost like a big city," said study researcher Josef Parvizi, an assistant professor of neurology at Stanford University."We want to know exactly which district in the city is involved," Parvizi said. "It tells us exactly where to look for the network of laughter."
Parvizi and colleagues reviewed brain imaging information from 100 patients with gelastic epilepsy. Because the condition is so rare, ahe study of this size was hard to achieve, Parvizi said.
In every case, the patient's brain lesions were centered in an area of the hypothalamus called the mammillary bodies. The findings suggest laughing involves the mammillary bodies and areas connected to them.
The researchers also found that the longer patients had had their seizures, the more likely they were to have a more severe form of gelastic epilepsy, in which patients develop additional types of seizures in addition to laughing seizures.
Gelastic epilepsy usually begins at age 3 or 4, according to Epilepsy Action, an epilepsy advocacy organization in the United Kingdom. The study suggests "if you let patients go untreated, the child's seizures will get worse," Parvizi said. "The sooner you stop it, the better it is."
The laughter in gelastic epilepsy usually occurs suddenly and is out of place, according to Epilepsy Action. The laughter is often abnormal, and usually described as being "hollow," "empty" and not very pleasant, Epilepsy Action says.
The new study was presented Sunday (Dec. 4) at the American Epilepsy Society meeting in Baltimore.
Pass it on: A region of the brain's hypothalamus may be involved in human laughter.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.