Processing of novel and familiar faces in infants at average and high risk for autism

The study investigated whether infant siblings of children with autism (sibs-ASD) process familiar and novel faces differently from typical infants and whether sensitivity to face familiarity is associated with infants' social and communicative behaviors. Visual event-related potentials (ERPs) were recorded in 35 infants, age 9 months ± 15 days (20 typical infants, 15 sibs-ASD) using an oddball paradigm presenting photographs of infants' mothers (70% of trials) and an unfamiliar female (30% of trials). Eye tracking responses to a different unfamiliar face were recorded to determine whether differences in gaze patterns might account for any ERP differences found. There were no group differences in the distribution, number or duration of fixations. Both infant groups differentiated between mothers and strangers, as reflected in amplitude modulations of posterior N290/P400 and frontal/central Nc responses. Group differences were present in the latency of the P400 response, where a delayed response to the stranger face was observed only in typical infants. Across both groups, shorter Nc latency to mother's face was associated with parental reports of stronger interpersonal skills. Individual differences in the speed of processing for novel vs. familiar faces may be an informative early marker of risk for atypical social development.