As gregarious animals, humans value social decision-making, which is a challenging activity that requires us to make real-time judgments based on our partners’ behavior. Imagine you invited a person to go on a date and saw a flash of unwillingness on his/her face. Before the person said anything, you made a quick decision to declare that you were joking. What neural mechanisms enabled you to make this swift decision?
The synchronization of brain activities in humans during social engagement is believed to facilitate social decision-making. The medial prefrontal cortex (mPFC), a brain structure, is believed to be associated with the generation of this synchronization. Because its exact mechanism is unknown, Lyle Kingsbury and his colleagues investigated the mPFC’s activity during social interactions at the single-cell and cell-population level in the paper Correlated neural activity and encoding of behavior across brains of socially interacting animals.
The activities of the dorsal mPFC (dmPFC) of pairs of mice engaging in social interactions were recorded. Correlated brain activities were observed across these animals, confirming the crucial role of this synchronization during their interaction. Remarkably, the researchers found two populations of dmPFC neurons: subject cells, which encode the behavior of the mouse, and opponent cells, which encode that of its social partner. This observation implied that animals hold dynamic mental representations of their social partners during social interactions.
DmPFC activities also have predictive values. If an animal’s social decision is preceded by highly synchronized dmPFC activities, the other animal will be more likely to respond to the decision – compared to when the preceding correlation is low. Also, the animals’ dominance relationship can be inferred by their dmPFC activities. The dominant’s subject cells were more active than their opponent neurons, while the opposite was observed in the subordinate animal. In other words, both animals paid more attention to the dominant’s behavior, compared to that of the subordinate.
The present study revealed the neural mechanisms underlying the synchronization of socially interacting brains. Abnormal social interactions have been found in mental diseases, such as autism spectrum disorders and schizophrenia. The current study helped scientists better understand the causes of these abnormalities and contributed to the improvement of their treatments.
Reference
Kingsbury L, Huang S, Wang J, Gu K, Golshani P, Wu YE, Hong W. Correlated Neural Activity and Encoding of Behavior across Brains of Socially Interacting Animals. Cell. 2019 Jul 11;178(2):429-446.e16. doi: 10.1016/j.cell.2019.05.022.