A developmental ERP study of verbal and non-verbal semantic processing.

To clarify how different the processing of verbal information is from the processing of meaningful non-verbal information, the present study characterized the developmental changes in neural responses to words and environmental sounds from pre-adolescence (7-9 years) through adolescence (12-14 years) to adulthood (18-25 years). Children and adults' behavioral and electrophysiological responses (the N400 effect of event-related potentials) were compared during the processing of words and environmental sounds presented in semantically matching and mismatching picture contexts. Behavioral accuracy of picture-sound matching improved until adulthood, while reaction time measures leveled out by age 12. No major electrophysiological changes in the N400 effect were observed between pre-adolescence and adolescence. When compared to adults, children demonstrated significant maturational changes including longer latencies and larger amplitudes of the N400 effect. Interestingly, these developmental differences were driven by stimulus type: the Environmental Sound N400 effect decreased in latency from adolescence to adulthood, while no age effects were observed in response to Words. Thus, while the semantic processing of single words is well established by 7 years of age, the processing of environmental sounds continues to improve throughout development.