Within- and Between-Channel Gaps Elicit Mismatch Negativity in the Aging Brain

This study examined how older and younger adults process silent gaps in auditory stimuli by recording cortical evoked potentials using a multi-deviant paradigm that is compared to a psychophysical gap detection task. Participants passively listened to pairs of noise markers separated by silent intervals. Markers were either spectrally identical (within-channel) or spectrally distinct (between-channel) narrowband noises. Seven gap durations served as deviants in a multi-deviant sequence. The deviance-related negativity (DRN) and the P2/P3a were recorded from fronto-central electrodes. Thirty-two participants with normal hearing or minimal hearing loss participated in this study. They were separated into an older adult (mean age = 63 years) and younger adult (mean age = 24 years) group. Gapped deviants elicited DRN in both within- and between-channel conditions. Age effects emerged in the DRN and peak-to-peak DRN-P2/P3a measure. Older adults showed longer DRN latencies and reduced amplitudes compared to the younger group. Condition effects showed contrasting DRN latency patterns between groups. P2/P3a responses alone did not show any condition or age-specific effects. Behavioral gap detection thresholds did not differ across conditions in older adults. Overall, results demonstrate that electrophysiological indices reveal subtle neural alterations in temporal resolution that may precede behavioral decline.