Mother recognition and preference after neonatal amygdala lesions in rhesus macaques (Macaca mulatta) raised in a semi-naturalistic environment.

Attachment to the caregiver, typically the biological mother, is crucial to young mammals' socio-emotional development. Although studies in nonprimate species suggest that the amygdala regulates social preference and attachment development, its role in primate filial attachment development has been little investigated and has produced mixed results. This study assessed the effects of neonatal amygdala- (Neo-A, N = 16) and sham- (Neo-C, N = 12) lesions on mother recognition and discrimination in macaques raised in species-typical social groups. Neonatal amygdalectomy did not affect social discriminative abilities and mother preference at 3 and 6 months of age, strongly suggesting that the amygdala is not involved in the cognitive processes underlying the development of filial attachment at least when the amygdala damage occurred after the third to fourth weeks of age. Nevertheless, as compared to sham-operated controls, amygdalectomized infants initiated physical contact with their mothers less frequently. The findings are discussed in relation to the known contribution of the amygdala to filial attachment in both rodents and humans.