The Brain Gears Up for Processing Faces Well Before Birth

Newborn babies are naturally drawn to faces, a trait which helps them bond with their mothers and other caregivers. New Yale research has now found that the functional brain network involved in processing dynamic faces in adults can be observed as early as the third trimester of pregnancy.

For many functional brain networks, development largely occurs after birth. The findings, recently reported in Imaging Neuroscience, offer the first evidence that the brain pathway that typically supports perception of socially engaging faces can already be detected in the womb.

Studying how this pathway unfolds during the fetal and neonatal periods may help researchers understand how neurodevelopmental disorders arise, the scientists say. This includes autism spectrum disorder, which has been associated with differences in social attention.

“For newborns, being able to orient toward socially engaging faces—smiling, vocalizing, making eye contact—is a very important survival skill, because it helps them bond with their caregivers,” says Katarzyna Chawarska, PhD, Emily Fraser Beede Professor of Child Psychiatry and the study’s first author. “In older individuals this function is supported by the social perception pathway. We now demonstrate that this pathway begins to assemble before birth.”

Last year, the researchers discovered that a brain network that processes dynamic faces, gaze, and speech—known as the social perception pathway—is detectable at birth. They also found that infants who had stronger connectivity in this pathway paid more attention to faces at 4 months old, which in turn predicted fewer social difficulties at 18 months.

“This was the first demonstration showing not only that this pathway may be present in elementary form at birth, but that it provides the scaffold for the development of social orienting skills in infancy,” Chawarska says.

In the latest study, the researchers explored whether the social perception pathway is also present during fetal development. Because there is considerable variability in how brains develop, the team needed to study a large number of participants to fully understand their developmental trajectories. So, they turned to the Developing Human Connectome Project, an open-source database that is collecting brain connectivity measurements from fetuses and neonates between 20 and 44 weeks post-conception. In total, they analyzed functional magnetic resonance imaging (fMRI) data from 167 fetuses and 477 neonates.

The scientists specifically looked at the activity of the social perception pathway involved in processing dynamic, speaking faces, as well as one other network associated with static face recognition known as the ventral pathway. Their analyses revealed that both pathways were active as early as 30 weeks into pregnancy, the beginning of the third trimester, but that the social perception pathway showed particularly robust growth during the pre- to postnatal transition and a high level of interconnectivity shortly after birth.

Across the third trimester, the fetal brain triples in weight. This period of growth is when many important brain networks begin to form, but for many of the functional networks, the assembly becomes apparent after birth. It is notable that the social perception pathway has already begun developing before the babies are born, adds Laura Ment, MD, professor of pediatrics (neurology) and senior author of the study.

The team’s next step is to follow infants from birth through toddlerhood to examine whether early characteristics of the social perception pathway are linked with later development in social engagement and communication.

“Our goal is to move beyond simply describing how these networks are organized at birth,” says Chawarska. “We want to understand what early brain organization can tell us about the processes through which children develop ways of engaging with and responding to the social world.”