Neurobiology of pregnancy and the postpartum period in the common marmoset

Preclinical data suggest pregnancy is associated with neurobiological changes in brain regions relevant to maternal behavior. Unfortunately, there is an absence of basic neurobiological information about the effects of pregnancy and the postpartum on the human brain. Moreover, we lack relevant studies in non-human primates that track changes in brain systems across pregnancy and parturition and their associations with maternal behavior. To bridge this gap, we examined the potential relationship between brain structure and function, and maternal behavior across pregnancy in the common marmoset (Callithrix jacchus). Eight nulliparous females (4 pregnant; 4 non-pregnant controls) were studied at four time points: pre-pregnancy baseline, gestation 1 (50-70days), gestation 2 (105-125days), and postpartum (3-14days). Infant-directed behavior was assessed using a custom-built T-Maze designed to assess responsiveness towards two infants. The number of times the female approached either infant and the overall pattern of movement was tracked using EthoVision and compared to non-pregnant multiparous and postpartum controls. Structural (T1-weighted and DTI) and functional (awake resting-state) MRI scans were collected on a 7 T Bruker scanner. Our data thus far show that among nulliparous females, infant-directed behavior decreased across gestation. During the postpartum period, the now primiparous females showed behavior equivalent to postpartum controls. Our preliminary observations support previous findings of infant avoidance in nulliparous females prior to parturition and increased infant responsiveness during the postpartum. Future analysis of our multimodal neuroimaging data will help elucidate the relationship between pregnancy and the postpartum, maternal behavior, and putative changes in the brain.