Roles of the basolateral amygdala and hippocampus in social recognition in rats.

Lesions of the amygdala or hippocampus have a large impact on social behavior of rats. In this study we investigated whether a social recognition test was also affected by those lesions. An NMDA-induced lesion of the basolateral amygdala did not impair the ability to distinguish a familiar from an unfamiliar juvenile rat. It was argued that the cortico-medial amygdala may be more important for social recognition than the basolateral amygdala. Fimbria-transected rats could no longer distinguish a familiar from an unfamiliar juvenile. Moreover, during all encounters they spent less time investigating the juvenile. The precise nature of this deficit, especially the reason for the overall reduced social investigation time, could not be specified with the classical procedure of the social recognition test.