Differential sex-independent amygdala response to infant crying and laughing in parents versus nonparents

Background: Animal and human studies implicate fore-brain neural circuits in maternal behavior. Here, we hypothesized that human brain response to emotional stimuli relevant for social interactions between infants and adults are modulated by sex- and experience-dependent factors. Methods: We used functional magnetic resonance imaging and examined brain response to infant crying and laughing in mothers and fathers of young children and in women and men without children. Results: Women but not men, independent of their parental status, showed neural deactivation in the anterior cingulate cortex, as indexed by decreased blood oxygenation level-dependent signal, in response to both infant crying and laughing. The response pattern changed fundamentally with parental experience: in the amygdala and interconnected limbic regions, parents (independent of sex) showed stronger activation from crying, whereas nonparents showed stronger activation from laughing. Conclusions: Our data show sex- and experience-dependent modulation of brain response to infant vocalizations. Successful recognition and evaluation of infant vocalizations can be critical for bonding mechanisms and for offspring well-being and survival. Thus, the modulation of responses by experience seems to represent an adaptive mechanism that can be related to reproductive fitness.