Effects of resocialization on post-weaning social isolation-induced abnormal aggression and social deficits in rats.

As previously shown, rats isolated from weaning develop abnormal social and aggressive behavior characterized by biting attacks targeting vulnerable body parts of opponents, reduced attack signaling, and increased defensive behavior despite increased attack counts. Here we studied whether this form of violent aggression could be reversed by resocialization in adulthood. During the first weak of resocialization, isolation-reared rats showed multiple social deficits including increased defensiveness and decreased huddling during sleep. Deficits were markedly attenuated in the second and third weeks. Despite improved social functioning in groups, isolated rats readily showed abnormal features of aggression in a resident-intruder test performed after the 3-week-long resocialization. Thus, post-weaning social isolation-induced deficits in prosocial behavior were eliminated by resocialization during adulthood, but abnormal aggression was resilient to this treatment. Findings are compared to those obtained in humans who suffered early social maltreatment, and who also show social deficits and dysfunctional aggression in adulthood.