PROJECT SUMMARY/ABSTRACT Affiliative caregiving behaviors are essential for the survival and well-being of a social species. Specifically, prosocial comforting behavior can improve the physical and mental health of distressed individuals. Similarly, parental care is critical for offspring survival and also benefits the welfare of offspring. However, despite the importance of both empathetic prosocial behaviors and parental caregiving for developing and maintaining social bonds, their underlying neural circuitry remain incompletely characterized. While prosocial care is primarily directed towards adult animals, a long-standing proposal for the origin of prosocial care points to potential evolutionary roots in parental care: the need to support helpless offspring drove the development of neural, chemical, and psychological sensitivity to detect contextual cues of others’ needs. The proposed research will explore the shared neural circuits underlying these behaviors, providing insight into the fundamental principles subserving social affiliation. While much is known about the positive control of parenting, the neural circuitry of comforting prosocial behavior is not as well defined. The medial preoptic area (MPOA) is a key region for regulating parenting behaviors. Recent evidence suggests the MPOA may also be involved in modulating prosocial comforting behavior in rodents. Other lines of evidence implicate the dopaminergic system in affiliative and parenting behavior through inhibitory inputs to the ventral tegmental area (VTA). This proposal hypothesizes that the inhibitory MPOA-VTA circuit is functionally significant as a shared node for prosocial and parental behaviors in mice. My central hypothesis will be tested in two specific aims: (1) determine if inhibitory MPOA neurons projecting to the VTA control affiliative allogrooming and parental behavior, and (2) characterize how these encode social sensory cues as well as offspring-directed and conspecific-directed caregiving behavior. Collectively, these experiments will expand our understanding of the neural circuits shaping both prosocial and parenting behaviors, which are critical to the formation of fundamental social bonds. A more robust mechanistic understanding of the MPOA-VTA and its functions in prosocial and parental circuits will offer insights into the long-postulated role of parental care in mammals as the origin of social affiliation.