RP301 - Electrophysiological Perspectives on Age-Related Changes in Auditory Function in Older Adults

Abstract:
The study examined electrophysiological markers of age-related auditory dysfunction and deteriorated speech-in-noise perception in older adults, and assessed the interrelationship between early and late stages of auditory neural processing using amplitudes and latencies. Auditory middle and late latency responses were recorded in young and older adults. Findings suggest that aging, combined with hearing loss, exacerbates the deterioration of auditory processing at central levels. Age-related enhancement in suprathreshold Pa amplitudes and prolonged N2 latencies serve as electrophysiological indicators of deteriorated speech-in-noise perception in older adults. Age-related variations in AEP amplitudes and latencies each may reflect distinct neural mechanisms in the auditory system.

Summary:

Background:
Age-related auditory changes at the cochlear level may affect neural processing across the auditory pathway in the aging auditory system, potentially leading to a decline in speech-in-noise perceptual ability in older adults. The study proposes three specific aims: (1) to investigate electrophysiological indicators of age-related changes in auditory neural processing, specifically examining the differential and compound effects of aging and hearing loss; (2) to identify electrophysiological correlates of declines in speech-in-noise perception in older adults; and (3) to explore the potential interrelationship between early and later stages of auditory neural processing in the aging auditory system.

The study included 30 young normal-hearing adults (YNH, M=21 years), 26 older adults with normal or near-normal hearing (ONH, M=63.9 years), and 26 older adults with age-related hearing loss (OHL, M=72.8 years). Auditory middle latency responses (AMLR) and auditory late latency responses (ALLR) were monaurally and ipsilaterally recorded at rates of 11.1/s and 0.71/s, respectively, in separate runs. The synthesized speech /ba/ was presented at 110 dB peSPL in quiet and 12-talker babble noise conditions set at 65 dBA. Pa of AMLR and N1-P2-N2 of ALLR were analyzed and correlated with low-predictability (LP) scores of the revised Speech Perception in Noise (R-SPIN) test. The correlations between the Pa component of AMLR and the N1, P2, and N2 components of ALLR were computed for both amplitudes and latencies.

Results:
The effects of aging revealed significantly enhanced Pa and N1 amplitudes and significantly prolonged Pa, P2, and N2 latencies in ONH relative to YNH group. The effects of hearing loss revealed significantly prolonged N2 latencies in OHL relative to ONH group. The compound effects of age-related hearing loss revealed significantly enhanced amplitudes and significantly delayed latencies across all AEP components in OHL relative to YNH group, indicating a stronger impact on age-related changes in auditory neural processing. In the babble noise, all groups demonstrated reduced AEP responses with a marked delay in latency, indicating noise-induced neural disruption. This effect was more pronounced in older groups, especially in the OHL group. Enhanced Pa amplitudes and prolonged N2 latencies were significantly correlated with lower R-SPIN scores in both older groups. Significant amplitude-based correlations were found in both older groups, but not in the young group. This suggests that young adults efficiently filter out irrelevant neural information in auditory centers, while there's an information overload in the aging auditory pathway. Latency-based correlations were significant in all groups, indicating the impact of subcortical neural timing on neural transmission time along the auditory pathway.

Conclusions:
The study suggests that when aging interacts with hearing loss, it amplifies the age-related deterioration in auditory neural processing at subcortical and cortical levels. Age-related enhancements of suprathreshold Pa amplitudes and age-related prolongations of N2 latencies may serve as electrophysiological correlates of age-related declines in speech-in-noise perceptual ability. Age-related enhancement in suprathreshold Pa amplitudes suggests suprathreshold auditory processing deficits and prolonged N2 latencies indicate slower temporal processing speed. Age-related variations in AEP amplitudes and latencies may reflect distinct neural mechanisms in the auditory system.