Event-related potentials in year-old infants: relations with emotionality and cortisol

Event-related potentials (ERPs) were recorded from year-old infants presented with sets of familiar faces presented frequently and infrequently, and a set of novel faces presented infrequently. The normative response of infants in this sample was a late positive slow wave to the Infrequent Familiar faces, and a return to baseline to the Frequent Familiar and Infrequent Novel faces (although there was a tendency for some infants to show a positive slow wave to the latter events). A factor score based on data from frontal and central leads that reflected this normative pattern was significantly associated with infant emotional behavior and cortisol. Infants scoring higher on the normative ERP factor were more distressed during separation, were reported by their parents to smile and laugh more, and had lower cortisol concentrations during ERP testing. These data were interpreted as reflecting the coordination of adaptive responding among different physiological and behavioral systems.