The effects of neonatal lesions in the amygdala or ventral hippocampus on social behaviour later in life.

Disruption of normal social behaviour is seen in psychiatric neurodevelopmental disorders like schizophrenia or autism. In a rat model of neurodevelopmental disorders we investigated the social behavioural changes after damage of limbic brain areas, at two early stages of life. The effects of ibotenic acid lesions made on day 7 or 21 of life in the amygdala (AM) ((baso)lateral/medical) or ventral hippocampal area on social play behaviour, social behaviour unrelated to social play behaviour early in life, and social behaviour in adulthood were assessed. Lesions of the AM, but not lesions of the ventral hippocampal area, resulted in decreased social play behaviour, and no differences were found between lesions made on day 7 or 21 of life. Social behaviour unrelated to social play behaviour early in life and in adulthood was decreased in animals lesioned in the AM on day 7 but not in animals lesioned on day 21 of life. This effect was particularly present in animals with an additional lesion in the medial nuclei of the AM. Lesions in the ventral hippocampal area did not affect social behaviour. It is concluded that the AM is an important structure for social play behaviour. The effects on social behaviour that are dependent on the day of lesioning (day 7 vs. 21) are an indication of a neurodevelopmental deficit of structures connected to the (medial part) of the AM. Copyright 2002 Elsevier Science B.V.