Neuronal ensembles in the amygdala allow social information to motivate later decisions

Abstract

Social experiences carry tremendous weight in our decision making, even when social partners are not present. To determine mechanisms, we trained female mice to respond for two food reinforcers. Then, one food was paired with a novel conspecific. Mice later favored the conspecific-associated food, even in the absence of the conspecific. Chemogenetically silencing projections from the prelimbic subregion (PL) of the medial prefrontal cortex to the basolateral amygdala (BLA) obstructed this preference while leaving social discrimination intact, indicating that these projections are necessary for socially-driven choice. Further, mice that performed the task had greater densities of dendritic spines on excitatory BLA neurons relative to mice that did not. We next induced chemogenetic receptors in cells active during social interactions – when mice were encoding information that impacted later behavior. BLA neurons stimulated by social experience were necessary for mice to later favor rewards associated with social conspecifics, but not make other choices. This profile contrasted with that of PL neurons stimulated by social experience, which were necessary for choice behavior in social and non-social contexts alike. The PL may convey a generalized signal allowing mice to favor particular rewards, while units in the BLA process more specialized information, together supporting choice motivated by social information.SIGNIFICANCE STATEMENTSocial experiences color choices, even when social partners are not present. For instance, we might favor a restaurant because it is where we had a memorable first date. We demonstrate that projections from the prelimbic cortex (PL) to basolateral amygdala (BLA) are required for socially-driven decisions – that is, for mice to favor a familiar food previously associated with a conspecific. Neuronal ensembles in the BLA stimulated by social experience appear specialized to socially-driven choices, while ensembles in the PL are not. The BLA may form social memories, which, with PL input, enable organisms to prioritize social information in later action.