Cortical auditory evoked potential in aging: effects of stimulus intensity and noise.

OBJECTIVE: Older adults often have more difficulty understanding speech than younger adults do, particularly in the presence of noise. Such age-related speech perception difficulties may be related to declines in central auditory processing. Additionally, it has been hypothesized that impaired auditory processing might be related to neural dysynchrony. The purpose of this study was to examine the effects of stimulus intensity and noise on the N1-P2 response in younger and older normal-hearing adults.

METHODS: Eight younger and 8 older normal-hearing adults participated in this study. Brief 100-ms tones (1.0 kHz, 100-60 dB SPL) in quiet and in continuous broadband noise (70 dB SPL) were used to evoke the N1-P2 responses. The N1-P2 components were analyzed as a function of stimulus intensity in both groups.

RESULTS: N1 latencies to tones in quiet for older adults were delayed only at 60 dB SPL compared with those for younger adults. Additionally, N1 latencies to tones in noise were prolonged in older adults compared with those in younger adults even at 70 dB SPL (SNR = 0). No significant age effects were observed for the P2 latencies and N1-P2 amplitudes between the groups.

CONCLUSION: N1 latency to tones with lower intensity and noise were delayed in older adults compared with those in younger adults. These stimulus intensity and noise issues can affect synchronized neural activity underlying the auditory processing and may provide a partial explanation for the difficulties shown by older adults in understanding speech.