PROJECT SUMMARY/ABSTRACT Social perception is a fundamental feature of social communication. The ability to recognize social cues of others is critical to forming meaningful social relationships. Deficits in social perception can lead to impaired social coordination, resulting in loneliness and isolation that severely impacts well-being. This coordination is evident within the dynamic social interactions that occur in social hierarchies. In social hierarchies, individuals need to recognize social cues related to status (status signals) and use this information to determine how they socially interact. However, our knowledge of how the brain receives and transforms status signals into socially competent behavioral output remains limited. We have demonstrated that male and female mice form highly linear social hierarchies where each individual has a unique rank and shows appropriate social behavior to higher and lower ranked individuals. We have also found that the medial amygdala (MeA) and the ventral premammillary nucleus (PmV) show differential patterns of neural activity when individuals are exposed to dominant versus subordinate olfactory status signals. Based on these findings we hypothesize that social signal responsive neurons exist in the MeA and PmV that processes social status information before sending outputs to downstream hypothalamic nuclei which guide the expression of behavior. We will combine our innovative social hierarchy paradigm with cutting-edge molecular tools to test this hypothesis in males and females. In Specific Aim 1, we will test if the MeA and PmV contain neuronal subpopulations that are sensitive to status signals. Using single nucleus RNA-Seq (snRNA-Seq) we will measure the transcriptional activation of MeA and PmV cells. Using cellular compartment analysis of temporal activity by fluorescent in situ hybridization (catFISH) in conjunction with RNAScope we will characterize spatial and temporal transcription patterns in the MeA and PmV in response to status signals. Using this approach, we will be able to determine if distinct or overlapping neuronal subpopulations process dominant and subordinate social signals. In Specific Aim 2, we will use vivo morpholinos to directly test the role of oxytocin and vasopressin receptors in the MeA and PmV in coordinating social status perception. These receptors have a well-established role in social behavior and are expressed in the MeA and PmV. We will selectively reduce the translation of each receptor type, and then test how this manipulation impacts the ability of animals to engage in social discrimination and maintain social dominance relationships. If successful, results from these studies will establish a novel paradigm for understanding the neural processing of social perception, establish the MeA and PmV as key brain regions in the discrimination of social signals, identify subpopulations of neurons that respond to status cues, and determine the roles of oxytocin and va...