Rough-and-Tumble Play The Brain Sources of Joy
Authors: Panksepp Jaak 
Published: November 2023

Abstract
When children are asked what they like to do more than anything else, the most common answer is “to play!” It brings them great joy. And roughhousing play is the most fun of all, even though most investigators recognize other types such as “object play” and “fantasy play.” Although thousands of papers have been written on the topic, play is still considered a frivolous area of inquiry among most neuroscientists. Only recently have some become interested in the underlying brain issues. Now increasing numbers of investigators are beginning to realize that an understanding of play may reveal some major secrets of the brain and yield important insights into certain childhood psychiatric problems such as autism and attention deficit disorders (or hyperkinesis, as it used to be known). It is now certain that the brain does contain distinct neural systems devoted to the generation of roughhousing or rough-and-tumble (RAT) play. Indeed, one of the best species for systematic study of this behavior is the laboratory rat, and practically all the work summarized here is based on such play in rats. Although our knowledge about the underlying PLAY systems remains rudimentary, RAT play appears to be intimately linked to somatosensory information processing within the midbrain, thalamus, and cortex. Certain synaptic chemistries are especially effective in arousing play (e.g., acetylcholine, glutamate, and opioids), while others reduce playful impulses (e.g., serotonin, norepinephrine, and GABA), but neuro-pharmacological studies tell us little about the adaptive function(s) of play. There is an abundant theoretical literature regarding these functions, comparable to that found in dream research, but relevant data are decidedly scarce. The description from a leaflet in a box of Lego® toys says it all. Now it is necessary to judge the various possibilities with rigorously conducted experiments. Fortunately, roughhousing PLAY systems appear to be conserved in the brains of many mammalian species, and we should be able to obtain a credible answer to the functional questions, even for humans, by carefully analyzing animal models. We anticipate that play will be found to have many beneficial effects for both brain and body, including the facilitation of certain kinds of learning and various physical skills. Most important, play may allow young animals to be effectively assimilated into the structures of their society. This requires knowing who they can bully, and who can bully them. One must also identify individuals with whom one can develop cooperative relationships, and those whom one should avoid. Play probably allows animals to develop effective courting skills and parenting skills, as well as increasing their effectiveness in various aspects of aggression, including knowledge about how to accept defeat gracefully. It seems that most of the basic emotional systems may be recruited at one time or another during the course of play, and in higher organisms, play may encourage organisms to test the perimeters of their knowledge. In short, the brain’s PLAY networks may help stitch individuals into the social fabric that is the staging ground for their lives.