Event-related potentials elicited in mothers by their own and unfamiliar infants' faces with crying and smiling expression.

Crying by an infant signals an urgent desire for care and protection. Because of the special relationship between a mother and her infant and the signal value of her crying, it is plausible to suggest that the maternal brain efficiently processes crying by infants. In the present study, we examined this hypothesis by measuring event-related potentials in mothers while they observed crying or smiling by their own or unfamiliar infants embedded within a train of neutral expressions. We found that the amplitude of the face-specific N170 component was enlarged for crying regardless of familiarity. The P300 component, which reflects a later cognitive evaluation stage of stimulus processing, was decomposed into functionally distinct components by temporal principal component analysis. The amplitude of the third temporal factor, which corresponds to the earliest portion of the P300, was larger when a mother observed her own infant crying than for the other conditions. Moreover, onset latency of P300 was shortest when mothers observed their own infant crying. These results indicate that mothers process their own infant's crying more efficiently than smiling by their own infant or crying by an unfamiliar infant.