‘Giggling’ Rats Help Scientists Determine Our Moods And What Makes Us Ticklish

These “giggling” rats are doing it all for science, and they’re doing it because they’re in a good and ticklish mood. And, as a new study explains, the research involving the rats could explain what makes us humans ticklish in the first place.

The new study was conducted by Shimpei Ishiyama and Michael Brecht, two researchers from Germany’s Humboldt University who went on the “weirdest job ever,” tickling rats for the sake of scientific research. According to the findings of their study, rats only enjoy being tickled if they’re in a good mood at the time, and feeling safe from danger. Ishiyama and Brecht were also able to determine the part of a rat’s brain that triggers ticklishness, and were able to activate that spot to induce happy behavior in the animals.

Aside from their unusual form of giggling, which was so high-pitched it couldn’t be heard by humans, the rats quite interestingly leapt in the air at random while in a happier mood stimulated by the tickling. These happy leaps were dubbed as Freudensprunge, or “joy jumps.”

Giggling lab rats teach scientists about how tickling works: https://t.co/r6UnoXMBqx http://pic.twitter.com/BYrkWjNCNf

— Discover Magazine (@DiscoverMag) November 12, 2016

“This is the only deep scientific approach we currently have to understanding the evolutionary sources of our own emotions, which are very important for deepening psychiatric understanding and treatment of affective disorders,” said neuroscientist Jaak Pansepp in an interview with Popular Science.

While not involved in the new study, Panskepp was the first researcher to discover rats are ticklish, having done so in 1999. He had found that rats, once tickled, would let out high-pitched squeaks that they would usually make when confronted with food, a chance to play, and other positive stimuli. And while the human ear wouldn’t be able to pick up their giggling, the rats’ “ultrasonic vocalizations” are as close as they get to resembling laughter.

According to a report from The Smithsonian, the giggling rats were so happy with the tickling that they had chased the researchers’ hands around.

“They were so excited,” said lead author Ishiyama, speaking to The Smithsonian. “They were jumping around and they chased my hand. Pretty much like human kids, giggling and chasing around, playing rough and tumble.”

Conversely, things were very different for the rats when they were exposed to stressful situations. Ishiyama and Brecht tried tickling the rats while bright lights were shone above them to provoke the nocturnal creatures. With the lights stressing the animals out, they were much less likely to giggle, joy jump, or express any feelings of happiness.

The Smithsonian report also cited a long-ago study from Charles Darwin, where he wrote in his 1872 book The Expressions of the Emotions in Man and Animals that a creature’s mind “must be in a pleasurable condition” for tickles to actually cause laughter. But the true scientific link between tickling and laughter had long been a mystery, and one that the researchers sought to solve.

To this end, Ishiyama and Brecht inserted a wire into the rats’ brains to track neuron activity during the tickling sessions. As it turned out, the most active part of the brain was the somatosensory cortex, which is normally linked to direct touch. But this only applied to times when the animals were giggling; when the rats were under stress, the region was much less active.

Rats ARE ticklish – but they only 'laugh' when they are in a good mood https://t.co/gcUEkvjVo0

— Daily Mail Online (@MailOnline) November 11, 2016

All told, the researchers believe that the somatosensory cortex may play a much larger role in determining one’s mood and reaction to tickles, not only for rats, but maybe also for humans.

“Traditionally the somatosensory cortex is known to represent just the tactile information on the body surface,” Ishiyama said. “Mood is thought to be handled somewhere else in the brain. But the somatosensory cortex is actually doing more.”

But what about creatures that don’t respond to tickles as well as rats and humans do? Bowling Green State University researcher Jeffrey Burgdorf, who served as a peer reviewer on the Humboldt University study, said that tickling is a “pro-social” behavior, hence the presence of giggling rats (and a variety of other animals who enjoy being tickled), as well as animals such as mice that don’t show ticklishness.

[Featured Image by Taylor Weidman/Getty Images]

‘Giggling’ Rats Help Scientists Determine Our Moods And What Makes Us Ticklish is an article from: The Inquisitr News