The study had three Rhesus monkeys sit around a rotary table and take turns to offer an apple slice to one of the other two monkeys. At the same time, the researchers recorded the activity of individual neurons in a brain area known to play a role in social cognition, called the dorsomedial prefrontal cortex (dmPFC).
During these interactions, the monkeys reciprocated past offers of an apple slice and retaliated when they did not receive a slice from another. The researchers’ recordings identified distinct neurons in the dmPFC that responded to the actions of other monkeys in the group. Certain neurons were activated with a particular action and outcome of specific individuals within the group (such as a neighbor monkey offering an apple slice leads to the outcome of receiving the reward). Many of the neurons encoded information not only about the actions and outcomes of specific individuals but also about their past behavior. This information about past interactions with group members influenced an animal’s upcoming decisions to reciprocate or retaliate, and investigators could use the neuronal information to predict which monkey would receive an apple slice from a particular monkey even before it was offered.
“This finding suggested that the dmPFC plays a role in strategic decisions. To test this idea, we disrupted the normal activity in this area and found that the animals were less likely to reciprocate,” says lead author Raymundo Báez-Mendoza, PhD, an investigator in the Department of Neurosurgery at MGH.
The results suggest that the dmPFC plays an important role in mapping out our actions and outcomes as well as the actions of others. “In neuropsychiatric conditions in which this ability is compromised, treatments aimed at improving the functioning of this brain area, either directly or indirectly, might improve peoples’ lives,” says senior author Ziv Williams, MD.
Co-authors include Emma P. Mastrobattista, and Amy J. Wang, MD.
Funding for the study was provided by the National Institutes of Health, the Brain & Behavior Research Foundation, the MGH Fund for Medical Discovery, and the Howard Hughes Medical Institute.
About the Massachusetts General Hospital
Massachusetts General Hospital, founded in 1811, is the original and largest teaching hospital of Harvard Medical School. The Mass General Research Institute conducts the largest hospital-based research program in the nation, with annual research operations of more than $1 billion and comprises more than 9,500 researchers working across more than 30 institutes, centers and departments. In August 2021, Mass General was named #5 in the U.S. News & World Report list of “America’s Best Hospitals.”