Proceedings of Meetings on Acoustics

We investigated the morphology of the N1-P2 auditory evoked potential (AEP) to changes in amplitude rise time (ART) and rate of formant transition (RFT) of consonant-vowel pairs (CVs) in 4-6-year olds and adults. In the AEP session, individuals listened passively to the CVs /ba/, /wa/, and a /ba/ with a superimposed slower-rising /wa/ envelope (/ba/wa). In the behavioral session, individuals listened to the same stimuli and judged whether they heard a /ba/ or /wa/. In 6-year olds and adults, the N1-P2 amplitude reflected a change in RFT (/ba/wa and /wa/) but not in ART (/ba/ and /ba/wa). In contrast, in the 4-5-year olds, the poorly developed N1-P2 did not show specificity to changes in RFT or ART. Behaviorally, 6-year olds and adults relied more strongly on RFT cues (classified /ba/wa as /ba/) during phonetic judgments, as opposed to 4-5-year olds which utilized both cues equally (chance level). Our findings suggest that following age 4-5, the development of the N1-P2 AEP, representing maturation of synaptic connections in the superficial layer of the auditory cortex, reflects a shift toward weighting of spectral dynamics more than amplitude dynamics during /ba/ /wa/ phonetic categorization.