Social behaviors are crucial to all mammals. Most previous research on social behavior has focused on the brain's circuits for hardwired behaviors, like aggression, sex, or mothering. Although the prelimbic cortex (PL, part of medial prefrontal cortex) has been implicated in social behavior, it is not clear which neurons are relevant or how they contribute.
In their experiments, the team gave two mice a chance to socialize in a cage that limited the mobility of one of the mice (the "social target"), so the test mouse could choose whether or not to go to the target for friendly behaviors like sniffing and grooming. Later, the test mouse was reintroduced to the test cage. When the researchers used optogenetics, a biological technique which involves the use of light to control neurons, to inhibit the key social-spatial pathway they had identified in the brain, the test mouse wandered freely through the space. When they didn't inhibit that circuit, the test mouse preferred to spend time where it remembered socializing with the other mouse.
Authors show that PL-NAc neurons encode a conjunction of social and spatial information and PL-NAc neurons bidirectionally modulate social-spatial learning.