Maturation of Cortical Auditory Evoked Potentials in Response to Tones and Noise During Adolescence and Young Adulthood

PURPOSE: Comprehension of speech in noise and noise-vocoded speech develops well into adolescence. To further understand the cortical maturation underlying these changes, we (a) compared cortical auditory evoked potentials (CAEPs) to tones and noise in adolescents and young adults and (b) examined if CAEPs predict degraded-speech perception. METHOD: Obligatory CAEPs were passively recorded in response to 1000-Hz pure tones and bandpass noise in 94 normal-hearing participants (aged 10-23 years). Listeners also repeated speech in noise and noise-vocoded sentences. RESULTS: P1 and N1 latencies shortened with age, whereas N2 latencies lengthened with age. P1 and N2 amplitudes decreased with age, whereas N1 and P2 amplitudes increased with age. The estimated age of maturation differed across the four peaks. Regardless of age, P2 latencies were shorter, N1 and P2 amplitudes were smaller, and N2 amplitudes were greater in response to noise, when compared to tones. Differences in CAEP responses to noise versus tones predicted noise-vocoded speech perception, although the major predictor for both forms of degraded speech was age. CONCLUSIONS: Consistent with previous work, CAEPs continued to mature throughout adolescence. Differences in CAEP responses to tones and noise were similar across age, suggesting that adolescents' neural responses were not disproportionately affected by noise. Differences in the neural encoding of tones and noise contributed to the perception of noise-vocoded speech but not of speech in noise, suggesting that different mechanisms underlie the processing of these two types of degradation. These results have implications for understanding auditory cortical development and degraded-speech perception.