Circuit and synaptic plasticity mechanisms of approach and avoidance social behavior.
Social behavior is defined as any modality of communication and interaction between two or more conspecifics. These behaviors, which include affiliative and antagonistic interactions, are exhibited by all sexually reproducing species, they are characterized by high-level complexity of communication through multiple sensory modalities and they are essential for survival. Humans and other animals living in groups continuously experience situations in which they need to select appropriate behavioral responses upon exposure to conspecifics. At the very basis of this social behavior, an individual needs to decide for example whether to approach (positive or appetitive) or avoid (negative or aversive) other individuals. Here, using mice, we will investigate the brain circuits and synaptic mechanisms involved in conspecific approach and avoidance behavior. The Nucleus Accumbens (NAc) is a key region of the mesocorticolimbic circuits for evaluating appetitive and aversive information. Recent studies have revealed the importance of NAc in social behavior, but which neurons within this structure are relevant and how they contribute to conspecific interaction is largely unknown. We hypothesize that different populations of neurons within the NAc orchestrate and integrate different types of socially relevant information to initiate the appropriate behavioral response. Using in vivo and ex vivo recordings and circuit-specific optogenetic manipulations in specific social interaction conditions, we will investigate how the NAc integrates information about conspecifics and how it incorporates learned associations to initiate conspecific approach or avoidance.  This study will thus identify and functionally characterize the circuit and synaptic mechanisms controlling socially appetitive and aversive stimuli, and hence pave the way for a causal understanding of the processes underlying disruption of complex social behaviors in psychiatric disorders.