The medial and lateral cell groups of the sexually dimorphic area of the gerbil hypothalamus are essential for male sex behavior and act via separate pathways.

Male reptiles, birds and mammals do not copulate if the medial preoptic area (MPOA) is destroyed but the MPOA cell groups necessary for male sexual behavior were not known. Here, two cell groups essential for copulation are identified in the sexually dimorphic area (SDA) of the gerbil (Meriones unguiculatus) MPOA. Bilateral cell-body lesions of either the medial or lateral SDA eliminated mating in sexually experienced male gerbils given testosterone. Nearby MPOA lesions did not. The medial and lateral SDA affect sex behavior via separate pathways since lesioning the medial SDA on one side of the brain and the lateral SDA on the other did not stop sexual behavior.