We may think of laughter as a particularly human trait, but scientists have known since 2016 that rats have the ability to “laugh” when they are tickled or take part in a game of chase. Although these high-pitched vocalizations are beyond the range of human hearing, they can be detected with specialized microphones.
More recent research, conducted at Germany’s Humboldt University of Berlin, has identified an area of the rodent’s midbrain that appears to become activated when they play or are tickled. A team of neuroscientists led by Prof. Michael Brecht recorded the vocalizations of rats in a laboratory setting while being tickled on their backs or bellies, chasing the researchers’ hands, or socializing with other rats.
Implanted electrodes revealed that when the rats laughed, the periaqueductal gray area in their midbrain became especially active. The converse was true when the researchers inhibited this part of the brain with drugs: the rats seemed to lose interest in both laughter and play. Similarly, there was much less activity in this brain region when the rats were stressed after being moved to a different enclosure; unsurprisingly, they also stopped squeaking. These findings suggest that the desire to play is innate, hardwired deep into the mammalian brain.
Brecht and other researchers have stressed the need for more research to scrutinize the important yet often overlooked subject of play. These findings contribute to an existing body of research suggesting that a lack of play can result in depression, anxiety, the inability to form relationships, and a loss of resilience. It may even be detrimental to brain development.
Play like a rat:
- The Humboldt University scientists hope that by studying the brains of rats during times of play and laughter, they’ll develop a better understanding of the human brain at play.
- Like humans, rats appear to have a surprisingly well-developed ability to play; in previous studies, they were taught to play (and apparently enjoy) games of hide-and-seek with the researchers.
- In addition to its role in play, the periaqueductal gray area is also thought to be involved in the fight-or-flight response.
