Non-overlapping social and food reward representations in the basolateral amygdala

Abstract

The ability to consider and appraise positively valenced stimuli in the environment, such as food and social interaction, to guide appropriate action is important for survival of most animals. Several studies have compared how food and social rewards are represented in different regions involved in reward processing and found either overlapping or distinct representations. In the basolateral amygdala (BLA) there seems to be opposing evidence for both shared and unique encoding of social and nonsocial stimuli. In our recent work, we found that the medial prefrontal cortex (mPFC), a region reciprocally connected to the BLA, has distinct social and food representations using a novel self-paced two-choice assay. Given the BLA and mPFCs differing roles in reward processing, it is important to understand how these two nodes may differ in their encoding reward types within the same assay. To resolve how the BLA encodes social and food information, we recorded the activity of individual BLA neurons in female and male mice during a two-choice social-sucrose operant task. We found that BLA neurons robustly and distinctly respond to social and food reward. In contrast to the mPFC, BLA neurons did not show a bias towards social reward responsiveness and instead showed equal social/sucrose representation, in males, or a sucrose reward bias, in females. BLA neurons were sensitive to internal state - water deprivation increased the proportion of sucrose reward responsive neurons. Additionally, sucrose reward responsive BLA neurons were differentially sensitive to reward omissions, such that neurons that were excited by sucrose reward were more sensitive to reward omissions compared to those inhibited by reward. Together, these findings demonstrate distinct, heterogeneous response profiles within the BLA to social and food rewards, in a manner different from the mPFC.