Developmental trajectories of the default mode, executive control, and salience networks from the third trimester through the newborn period

Social cognition is critical to early learning. Functional imaging studies in adults and older children suggest the involvement of the default mode (DMN), executive control (ECN), and salience (SAL) networks in social cognition. These networks are vulnerable to environmental insults, and abnormalities of intra- and inter-network connectivity of the three are emerging as biomarkers of neurobehavioral disorders. However, the developmental trajectories of the DMN, ECN, and SAL across the third trimester of gestation and perinatal transition remain largely unknown. Employing resting-state functional MRI studies at 30-32, 34-36, and 40-44 weeks postmenstrual age (PMA), we tested the hypothesis that both intra- and inter-network functional connectivity in the DMN, ECN, and SAL develop across the 30-46 weeks PMA time interval in a longitudinal/cross-sectional sample of 84 fetuses and neonates. A secondary analysis addressed the impact of maternal mental health assessed at 28 weeks PMA on tri-network development from 30-46 weeks PMA. The DMN, ECN, and SAL develop across the third trimester of gestation and the first postnatal month. At the intra-network level, significant increases occurred between 36 to 44 weeks PMA for all three, with network strength values significantly different from 0 beginning at 40 weeks PMA for all. Functional connectivity increased less rapidly in the DMN than in the ECN and SAL networks, suggesting slower maturation of the network subserving social interactions. In contrast, significant inter-network DMN-ECN connectivity greater than 0 was found from 36 weeks PMA through the first postnatal month, suggesting the emergence of inter-network functional connectivity in the fetal brain. Finally, higher maternal mental health symptoms measured at the beginning of the third trimester negatively affected the developmental trajectory of the SAL network across the critical time interval of 30 weeks to 44 weeks PMA. Together, these data provide a framework to compare fetuses and neonates at risk for neurobehavioral disorders and assess the impact of the environment on the developing brain. ### Competing Interest Statement The authors have declared no competing interest.