A comprehensive assay of social motivation reveals sex-differential roles of ASC-associated genes and oxytocin

Social motivation is critical to the development of healthy social functioning. Autism spectrum condition (ASC) is characterized in part by challenges with social communication and social interaction. The root of these challenges is hypothesized to be a deficit in social motivation, specifically in one or more subcomponents (e.g. social reward reward seeking or social orienting). Current social behavior assays lack the ability to quantitatively measure both social reward seeking and social orienting simultaneously. We have developed an automated socially-rewarded operant conditioning task coupled with video tracking, to quantify effort to achieve access to a social partner and concurrent social orienting behavior in mice. We established that adult wildtype mice will work for access to a social partner, that male mice exhibit greater social motivation compared to females, and there is high test-retest reliability in the task across multiple days. We then benchmarked the method with two test-case manipulations. We first tested a mouse model of Phelan-McDermid syndrome, a neurodevelopmental disorder associated with ASC. These Shank3B mutants failed to show social reward seeking and exhibited reduced social orienting. Next, we demonstrated that oxytocin receptor antagonism decreased social motivation in wildtype mice, consistent with its role in social reward circuitry. Intriguingly, only male mice were vulnerable to Shank3B mutation, while females were more vulnerable to oxytocin blockade, a double dissociation suggesting separate circuits for social motivation in male and female brain. Overall, we believe this method provides a valuable addition to the assessment of social phenotypes in rodent models of ASC and the mapping of potentially sex-specific social motivation circuits in the brain.