- In mouse studies, researchers have discovered how different areas of the brain help process information related to social status, competition, and other group dynamics.
- Understanding these mechanisms could help to better understand competitive behavior and certain mental health conditions and neurological disorders.
Most social species, including humans, naturally fall into hierarchies when in groups. An individual’s placement in these hierarchies can affect their behavior. Researchers are just beginning to understand how the brain responds to and helps drive complex group dynamics, including competition, dominance, and social norms.
In two new NIH-funded studies, researchers explored how the brain tracks social status and whether that predicts how well mice compete for resources. The results were published on March 16, 2022 in Nature.
In one study, a team led by Dr. Kay Tye, a Howard Hughes Medical Institute researcher at the Salk Institute, examined the brain activity of mice as they competed to drink a sweet liquid. The team housed mice together until a social order emerged. Next, the researchers trained each mouse alone for the liquid to appear in the cage after a sound was emitted. Next, the researchers tracked the mice’s brain activity as they competed in pairs to drink the liquid after it appeared. Dominant mice generally drank more fluid than subordinate mice.
The researchers found that the activity of neurons in a part of the brain called the medial prefrontal cortex (mPFC) differed during competition depending on the social rank of the opposing mouse. Brain activity in the mPFC could predict a mouse’s social ranking with 90% certainty. These brain patterns could also predict which mouse would win before the competition began. Although the dominant mice were usually the predicted winners, they weren’t always. This indicates that other factors, such as motivation and confidence, also played a role.
Other work found that information about social competition was routed from the mPFC to another area of the brain called the lateral hypothalamus. This region plays a role in many social behaviors. A group of cells connecting the two brain regions showed more activity when the mice drank the liquid during a competition than when they were alone.
In the other study, a team led by Dr. Ziv Williams of Massachusetts General Hospital tracked mice that foraged competitively for food. The team used wireless recording devices capable of picking up signals from single neurons in the brain.
They found that the activity of individual neurons in a region of the brain connected to the mPFC, called the anterior cingulate cortex (ACC), changed in relation to the social rank of competing mice.
ACC activity increased when an animal was most socially dominant in competition and decreased when it was not. The success with which the animals searched for food depended on their rank relative to their competitor. The more dominant ones were generally more successful.
The activity of ACC neurons also changed depending on whether the mouse had competed successfully in the past. This suggests that cells play a role in making decisions when mice encounter similar scenarios.
When the researchers used drugs to manipulate the activity of these neurons, they could influence the mice’s competitive strength. But this competitive drive was further influenced by the social rank of other foraging mice.
“Collectively, these neurons contained remarkably detailed representations of group behavior and their dynamics as the animals competed for food, in addition to information about available resources and the outcome of their past interactions,” Williams says. “Together, these neurons could even predict the animal’s future success long before competition began, meaning they likely drove the animals’ competitive behavior based on the people they interacted with.”
“Most social species organize themselves into hierarchies that guide the behavior of each individual,” Tye explains. “Understanding how the brain handles this can help us understand the interplay between social rank, isolation, and psychiatric illnesses, such as depression, anxiety, or even substance abuse.”
—by Sharon Reynolds
References: Cortical sets orchestrate social competition through hypothalamic outputs. Padilla-Coreano N, Batra K, Patarino M, Chen Z, Rock RR, Zhang R, Hausmann SB, Weddington JC, Patel R, Zhang YE, Fang HS, Mishra S, LeDuke DO, Revanna J, Li H, Borio M, Pamintuan R, Bal A, Keyes LR, Libster A, Wichmann R, Mills F, Taschbach FH, Matthews GA, Curley JP, Fiete IR, Lu C, Tye KM. Nature. Mar 2022;603(7902):667-671. doi: 10.1038/s41586-022-04507-5. Published online March 16, 2022. PMID: 35296862.
Funding: NIH National Institute of Mental Health (NIMH), National Institute of Neurological Disorders and Stroke (NINDS), National Center for Complementary and Integrative Health (NCCIH), and Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD); JPB Foundation; Dolby Family Fund; Simons Center for the Social Brain; Ford Foundation, L’Oréal for Women in Science; Burroughs Welcoming Fund; AI Institute; Shanghai Jiao Tong University; Shanghai Qi Zhi Institute; Shanghai Municipal Grand Science and Technology Project; Meta Technology Group; Autism Science Foundation; MGH-ECOR Fund; Brain and Behavior Research Foundation.