The cortico-medial amygdala in the central nervous system organization of agonistic behavior.

Previous studies suggested that the corticomedial amygdala is involved in agonistic behavior by affecting social learning processes. The present study shows that deficits in the avoidance of a dominant male rat conditioned by defeat were only observed after bilateral lesions restricted to the medial amygdala and not after destroying the cortical portion. These results are related to the specific afferent and efferent connections of the medial amygdala with other brain structures involved in the control of agonistic behavior. Within the corticomedial amygdala the medial amygdaloid nucleus was found to be a major recipient of afferents from the accessory olfactory bulb, but also a source of efferent projections to the ventrolateral aspects of the ventromedial hypothalamic nucleus and the ventral premammillary nucleus. A strong reciprocity exists in the connections between ventromedial hypothalamus and premammillary nuclei with the medial amygdala. The connections between the ventromedial hypothalamic and dorsal premammillary nucleus with the midbrain periaqueductal grey suggest an important role for the periaqueductal gray in the descending output in the anatomical substrate for agonistic behavior.