The Medial Extended Amygdala in Male Reproductive Behavior A Node in the Mammalian Social Behavior Network

ABSTRACT: Hormonal and chemosensory signals regulate social behaviors in a wide variety of mammals. In the male Syrian hamster, these signals are inte-grated in nuclei of the medial extended amygdala, where olfactory and vomer-onasal system transmission is modulated by populations of androgen- and estrogen-sensitive neurons. Evidence from behavioral changes following le-sions and from immediate early gene expression supports the hypothesis that the medial extended amygdala and medial preoptic area belong to a circuit that functions selectively in male sexual behavior. However, accumulated behavioral, neuroanatomical, and neuroendocrine data in hamsters, other ro-dents, and other mammals indicate that this circuit is embedded in a larger in-tegrated network that controls not only male mating behavior, but female sexual behavior, parental behavior, and various forms of aggression. In this context, perhaps an individual animal’s social responses can be more easily un-derstood as a repertoire of closely interrelated, hormone-regulated behaviors, shaped by development and experience and modulated acutely by the environ-mental signals and the hormonal milieu of the brain