New mouse study has revealed neurons in the brain that drive competitive interactions between individuals and play an important role in defining group social behavior. The findings, published in Nature by a team led by investigators at Massachusetts General Hospital (MGH), will be useful not only for scientists interested in human interactions, but also for those studying neurocognitive conditions characterized by altered social behavior, such as autism spectrum disorder and schizophrenia.
“Social interactions in people and animals most typically occur in big groups, and these group interactions play a key role in sociology, ecology, psychology, economics, and political science,” says lead author S. William Li, an MGH MD/PhD student. “What mechanisms in the brain drive the complex dynamic behavior of social groups is still unknown, in part because much neuroscience research has concentrated on the behaviors of pairs of people interacting alone. We were able to examine group behavior by inventing a paradigm that wirelessly monitored huge cohorts of mice through thousands of distinct competitive group encounters.”
Li and his colleagues discovered that the animals’ social ranking in the group was closely related to the results of competition, and the team discovered that neurons in the anterior cingulate region of the brain store this social ranking information to inform future decisions by examining recordings from neurons in the brains of mice in real time.
“These neurons collectively held remarkably detailed representations of the group’s behavior and dynamics as the animals competed for food, in addition to information about the resources available and the outcome of their previous interactions,” says senior author Ziv M. Williams, MD, a neurosurgical oncologist at MGH. “Together, these neurons could even anticipate the animal’s own future success far before competition began, implying that they most likely influenced the animals’ competitive behavior depending on who they interacted with.”
Manipulation of the activity of these neurons, on the other hand, has the potential to artificially raise or reduce an animal’s competitive effort, and so regulate their capacity to compete effectively against others. “In other words, we could carefully adjust up and down the animal’s competitive drive without influencing other parts of its behavior such as basic speed or motivation,” Williams explains.
The results suggest that competitive success is not just determined by an animal’s physical fitness or strength, but is also heavily impacted by brain signals that promote competitive desire. “These one-of-a-kind neurons can combine information about the individual’s surroundings, social group circumstances, and reward resources to compute how to best behave under given situations,” Li explains.
Identifying the neurons that control these characteristics may help scientists design experiments to better understand scenarios in which the brain is wired differently, in addition to providing insights into group behavior and competition in various sociologic or economic situations and other settings. “Many disorders manifest in aberrant social behavior that covers many dimensions, including one’s capacity to recognize social norms and to exhibit acts that may match the dynamical structure of social groups,” Williams explains. “Developing a knowledge of group behavior and competition is relevant to various neurocognitive illnesses, but how this occurs in the brain has largely remained unexplored until now.”
Omer Zeliger, Leah Strahs, Raymundo Báez-Mendoza, Lance M. Johnson, and Adian McDonald Wojciechowski are also co-authors.
The National Institutes of Health, the Autism Science Foundation, an MGH-ECOR Fund for Medical Discovery Fellowship, and a NARSAD Young Investigator Grant from the Brain & Behavior Research Foundation all contributed to this study.