PARTNER IDENTITY EFFECTS ON CEA-VTA CIRCUIT FUNCTION DURING SOCIAL INTERACTION

Social encounters are strongly influenced by partner-related factors including familiarity, sex, age, and social hierarchy. How neural circuits integrate these partner features and maintenance of social contact remains incompletely understood. We demonstrated that the CeA to VTA projection is essential for sustaining social interaction. We extend these findings by examining how this pathway contributes to maintaining contact with different types of social partners, including individuals of varying social status. Given the VTA’s central role in reward processing, we hypothesized that CeA-VTA signaling supports partner- dependent social motivation. To monitor reward-related neural activity during social encounters, adult C57BL/6J mice expressing GCaMP in the VTA were implanted with wireless fiber photometry. This approach allowed us to record population-level VTA activity during dyadic interactions with distinct partner categories, including familiar and unfamiliar
males of known hierarchical rank, juveniles, and females. Photometry revealed robust engagement of VTA networks during social contact, with activity patterns varying depending on partner identity and social context. To test the role of CeA-VTA projections, we optogenetically inhibited this pathway using eOPN3 expressed in CeA neurons with optical fibers targeting the VTA. Suppression of CeA-VTA signaling altered social dynamics in a context- and partner-dependent manner, reducing social contact duration and modifying approach behavior, while leaving object exploration unaffected. These results show that VTA population activity differs across social partners, reflecting partner-dependent engagement during interaction, while selective inhibition of CeA inputs to the VTA demonstrates that this pathway is crucial for maintaining ongoing social contact in a socially relevant context.