Tickled rats reveal brain structure that controls laughter

Amazing stuff! Who says that science is mostly serious? 😊

"... Of all mammalian behaviors, play is one of the least understood ... “Neuroscience tends to focus very much on aversive things,” ... such as the brain regions behind aggression and fear. Play remains a mystery. “There’s relatively little research on positive emotions,” ... “which I tend to think is a mistake.” ...

The research that does exist shows rats will keep playing even after their entire cortex, the part of the brain essential for consciousness and higher level behaviors, has been destroyed. This suggests that play, like fear, is instinctual. Some studies propose that a structure called the periaqueductal gray (PAG), which plays a role in vocalization, the fight-or-flight response, and other behaviors, might be involved. When rats play fight with one another, they exhibit behaviors that mimic fear and aggression. ...

Rats are capable of particularly complex forms of play similar to those seen in humans ... In one previous experiment, ... team even taught the rodents to play hide and seek. At the beginning of the game, a rat was enclosed in a box while a researcher hid somewhere in the room. The researcher then opened the box using a remote control, allowing the animal to jump out and begin “seeking.” When the rat successfully found the hidden scientist, it was rewarded with—you guessed it—a tickle. The rats were also given the opportunity to hide while the researchers looked for them, and they proved to be especially good at coming up with creative hiding spots. Their ability to strategize was “almost spooky,” ...
Past experiments have shown that when certain animals are deprived of play, they become depressed, fail to form relationships, and are less resilient to stressful situations. Lack of play has even been shown to stunt brain development. ..."

Tickled rats reveal brain structure that controls laughter | Science | AAAS Rodents’ squeaks may shed light on the neural mechanisms of play in humans

Rats “laugh” when tickled, although this sound is too high- pitched for humans to hear