Neurodevelopmental trajectories of face processing in infants: A review and future directions.

Face perception is integral for social development in infancy, and for skills such as joint attention, recognition, and emotion processing. This review synthesizes research findings over the past 25 years related to ERP biomarkers of face perception in infants. We review this literature as it relates to face perception in neurotypical infants and those at risk for, or diagnosed with, autism spectrum disorder (ASD). Future research may be able to utilize these neural signatures of face processing as 'biomarkers' to predict which infants are most likely to develop ASD, which is important for early diagnosis and intervention. The N290, P400, and Nc have all been highlighted as ERP components which relate to face processing. We discuss how nuances in these three components respond to face versus non-face stimuli and to emotional facial expressions in neurotypical (NT) infants. Evidence suggests that infants at high risk for ASD and those who go on to develop ASD have measurable differences in brain activity in response to faces compared to those at low risk and who do not go on to have ASD. Although differences in brain activity while viewing faces may not be observed between infants at high risk for ASD and those without at a single time point, longitudinal studies, studies with more varied stimuli, and studies utilizing source localization have uncovered differences. Finally, we present a novel hypothesis about developmental trajectories in both neurotypical children and those with ASD related to both face and non-face processing.