Sex differences in the neural circuitry of aggression

The social behavior neural network (SBNN) is a circuit composed of reciprocally connected limbic structures that regulate a range of social behaviors, including aggression. Although both males and females of many species display aggressive behavior, studies of the neural circuitry underlying aggression have focused almost exclusively on males. In the present study, we investigated sex differences in neuronal activation of the neural circuitry controlling aggression in Syrian hamsters (Mesocricetus auratus). We employed c-Fos immunohistochemistry to quantify neuronal activation following aggressive encounters between same-sex male and female dyads. Animals were tested in their home cage either alone (n=7 per sex) or with a same-sex, non-aggressive intruder (n=7 per sex) for 10 minutes. Our data revealed substantial sex differences in the neuronal activation of the SBNN following aggression. In some regions, neuronal activity changed in opposite directions in males and females compared to controls (e.g., posterior lateral septum), while in others, there was a change in neuronal activation in only one sex (e.g., medial amygdala). These findings support the hypothesis that the neural circuitry regulating aggression exhibits marked sexual differentiation.