Neurobiology of Social Behavior Circuits

Our genetic manipulation of pheromone signaling led to a novel assessment of the respective roles of the vomeronasal organ (VNO) and the main olfactory epithelium (MOE) in pheromone-mediated behaviors. We discovered that, in contrast to previous thinking, VNO activity is not required for the initiation of male-female mating behavior in the mouse, and instead, ensures sex discrimination among conspecifics. In contrast, MOE signaling appears essential to trigger mating in the mouse. In a follow-up study, we showed that female mice lacking TRPC2, an ion channel specifically expressed in the VNO and essential for vomeronasal signal transduction, display unique characteristics of male sexual behaviors and show defects in female-typical behaviors. These data led us to propose that functional neuronal circuits underlying both male-and female-specific behaviors exist in the mouse female brain, and that, in normal females, the vomeronasal system controls the sex-specificity of social behaviors by activating female-specific effector circuits, while repressing male-specific circuits.