Neuroscientist Michael Brecht publishes a study identifying a basic brain area that activates when rodents play, suggesting that playful behavior is an instinct.
Neurons in midbrain
On a regular workday, neuroscientist Michael Brecht enters his laboratory at the University of Humboldt in Berlin, dons his lab coat, and starts tickling his rats. It’s fun work—especially for the rats—but it’s also serious. Brecht leads a research team aiming to identify the part of the brain responsible for laughter and play.
This area is believed to be located in the periaqueductal gray, a group of neurons surrounding the midbrain, according to a study published this week in the journal Neuron.
Vocalizations like laughter
It’s the same brain region that controls sounds and the fight-or-flight response (which also activates during physical play). “We know that vocalizations like laughter are very important in play,” explains Brecht via video call. “That’s why we looked in that area.” When we play, laughter coordinates and directs the process.
It serves as a receipt of humorous intentionality, distinguishing between a fight and a game, a chase and a tag. It’s what turns a politically incorrect comment into a joke, the contextual backdrop that disarms a threat.
This also happens with rats. They laugh, in their way. They emit ultrasonic vocalizations at 50 kilohertz when playing or being tickled. But they only do so if they have a certain bond with the scientists. That’s why Brecht and his team needed an adaptation period with the rodents, and only then did they start tickling them with their fingers on the back and belly.
Measuring brain activity
They measured their squeaks and brain activity and discovered strong neural responses both to tickling and play in the lateral column of the periaqueductal gray.
Play as an Instinct “We had already observed that some of the high-level structures of the sensory cortex were activated during play,” explains the scientist. “But in this new study, we chose to analyze a more basic brain structure and saw that even by inhibiting high-level brain structures, the animals can still play.” This would demonstrate that play is a basic mechanism and an instinct.
Humor in animals
Humor is one of the least understood and studied animal behaviors, laments Brecht. “I think there has been a bias against studying it scientifically,” he says. “Most studies focus on understanding negative emotions like depression, anxiety, pain… and I have nothing against that, but positive emotions are also an important part of life,” he reflects. That’s why he’s committed to tickling rats.
Evolution of the characteristic panting
Play and humor are common traits among many mammals. Dogs, meerkats, and rats laugh. Primates do too. In fact, our laughter is believed to be an evolution of the characteristic panting that great apes do when playing.
Psychologist Marina Davila-Ross, from the University of Portsmouth (UK), analyzed digital recordings of tickle-induced panting in chimpanzees, bonobos, gorillas, and orangutans and found that the vocal similarities between the species matched their evolutionary relationships. Chimpanzees and bonobos, our closest relatives, have laughter most similar to humans.
What makes things funny
Caleb Warren, co-director of the Humor Research Lab at the University of Colorado, has been studying what makes things funny for 15 years. His conclusions with humans are not very different from what Brecht has compiled with rats. “People laugh with a violation of the status quo,” he points out in a video conference.
“When they perceive a transgression, but at the same time, they believe it’s harmless and has no significant consequences,”
Caleb Warren
Warren has developed this idea in the study “Benign Violations: Making Immoral Behavior Funny.”
Try tickling yourself!
This theory could help understand abstract concepts such as the boundaries of black humor and political correctness. But it also applies to something much more basic and primitive, like tickling. “It’s a physical attack, but delivered in a way that doesn’t hurt. And it comes from someone you trust,” he explains.
“Try tickling yourself: it doesn’t work, there’s no threat. If a stranger on the street approaches you and tries to tickle you, it’s not funny, it’s rather unsettling. That’s where there’s a transgression, but it’s not harmless.”
A form of communication
Laughter, in this way, is understood as a primitive form of communication. “It’s one of the few sounds we use to communicate before speaking, along with crying and screaming,” says Warren. “It predates verbal language in humans. And other animals laugh, but they don’t have verbal language. So, it probably conveyed something very important.”
Brecht doesn’t know if the noise rats make could be considered laughter, but it does share with it that it’s an unequivocal sign of happiness. This fact could be used to test the effectiveness of antidepressants in rodents or to understand how stress can affect our humor. The ultrasonic laughter of rats can tell us a lot about the mechanisms of play and humor.
Original source: This information was Initially covered by Elpais.com and has been translated for our readers.