PROJECT SUMMARY Positive social interactions are critical for mental wellness and physical health. Many mental and neurodevelopmental disorders affect or are affected by the motivation to socially engage. This motivation is influenced by a myriad of factors that include external environment, particularly social context, as well as internal factors such as stress, reproductive status, and energetic state. Typically, the influence of these factors on social motivation are studied in isolation; however, we know that outside of the laboratory these factors interact and are integrated with one another. This proposal makes use of a novel system, Alston’s singing mouse (Scotinomys teguina), to investigate the neural circuit integrating social context and one important dimension of internal state: perceived energy balance. Singing mice are an ideal species in which to investigate these questions, as manipulations to social environment (e.g. exposure to potential mates or playback of conspecific song) and hormonal state (e.g. androgens, glucocorticoids, and leptin) can all influence vocal engagement. Through three aims, I will test the hypothesis that cues of social context and energy balance are integrated in specific cell types in the paraventricular hypothalamus. In Aim 1, I will work in the lab of Peter Strick at the University of Pittsburgh, using rabies virus tracing of inputs to laryngeal muscle to identify the brain circuit underlying singing mouse vocalization. This aim will confirm that energetic-sensing nuclei sit upstream of the paraventricular hypothalamus in the singing mouse vocal circuit or allow me to refine my hypothesis and choose a new target nucleus if necessary. Next, I will work in the lab of my sponsor Steven Phelps, at the University of Texas-Austin to identify neurons integrating social context and perceived energetic state. In Aim 2 I will use the neural activation marker, phospho-S6, to test the hypothesis that paraventricular hypothalamus neurons increase activity in response to exposure to females, leptin injections, or both. Then, I will use PhosphoTRAP, a method of sequencing RNA from recently active neurons, to identify transcripts expressed by neurons of the paraventricular hypothalamus that are activated by female exposure, leptin injection, or both. Finally, in Aim 3, I will use single-nucleus RNA-sequencing of the paraventricular hypothalamus to identify cell types in the region and relate these to candidate markers found in Aim 2. This will allow me to determine whether transcripts enriched in active cells correspond to specific cell types. Together, these aims will identify a circuit and specific cell types within it that integrate social and internal cues that influence vocal effort, enhancing our understanding of the complex processes that drive social motivation and laying the groundwork for future studies of social motivation and mammalian vocalization using this novel species. Through this fellowship I will gai...