Auditory event-related potentials during phonetic and semantic processing in children.

This study was designed to follow the time course of different levels of linguistic processing using auditory event-related potentials (AERPs). A hierarchical set of acoustically controlled stimuli was used to elicit AERPs in 20 normal children who performed discrimination tasks involving pure tones, phonetic 'easy' and 'difficult' stimuli and semantic stimuli. Results show that (1) AERP latencies were similar for phonetic 'easy' and 'difficult' stimuli, (2) prolonged P(2), N(2) and P(3) latencies characterized semantic processing compared to phonetic processing, (3) a late negativity was elicited during semantic processing only, (4) P(3) amplitudes were larger over the left compared to right scalp during linguistic processing (phonetic and semantic) but were similar during nonlinguistic processing (pure tones) and (5) reaction time was found to be longest for semantic processing whereas performance accuracy was found to be an insensitive measure. These results provide insight into brain processes underlying the perception of speech. Furthermore, they support a dual model of speech perception that includes parallel and serial processing.