PP1002 - Aging Effects on the Pre-Attentive and Attentive Auditory Event-Related Potentials

Abstract:
The primary aim of this study was to use a series of auditory event-related potentials (ERPs) in groups of young and older adults to determine aging effects on auditory processing at the pre-attentive and the attentive levels. The secondary aim of this study was to determine the correlations among ERPs, subjective evaluation of hearing, and cognitive function. Twenty-six normal hearing (NH) young listeners (Y: aged 20-30 years) and ten older NH listeners (O: aged 50-60 years) participated. All participants were assessed with ERPs, psychoacoustic tests, the 5-item Speech, Spatial and Qualities of Hearing Scale (SSQ5) questionnaire, and cognitive tests.

Summary:
Rationale:
Hearing involves bottom-up and top-down auditory processes that work together to allow individuals to perceive sounds in our everyday environments. The bottom-up process involves the auditory system transmitting sound information from the auditory periphery to the cortex for pre-attentive sound registration, automatic sound differentiation, and higher-level processes. The top-down process involves a descending pathway exerting cognitive influences such as attentional control on the auditory cortex and lower levels of bottom-up processing to achieve optimal auditory perception. These auditory processes may be affected by aging, one of the most common causes of hearing dysfunction.
Using a variety of auditory event-related potentials (ERPs) that provide information on hierarchical auditory processing, one can specifically examine auditory functions at different levels, which is impossible if only behavioral testing is used, as the behavioral performance is the result of mixed effects of both bottom-up and top-down processes.
There are several studies examining aging effects on ERPs, but the authors reported mixed results. Some studies suggested that aging affects peripheral processing, which results in poorer ERPs in older adults; other studies suggested aging alone affects the top-down process more than the peripheral process. The primary aim of this study was to use auditory ERPs, including the late latency auditory evoked potential (LAEP), mismatch negativity (MMN), P3a, and P3b in groups of young and older adults with normal hearing to determine aging effects on auditory processing at the pre-attentive and the attentive levels. The secondary aim of this study was to determine the correlations among ERPs, subjective evaluation of hearing, and cognitive function.

Methods:
Twenty-six normal hearing (NH) young listeners (Y: aged 20-30 years) and ten older NH listeners (O: aged 50-60 years) participated. ERPs were recorded in response to an oddball stimulus paradigm consisting of a standard stimulus (750 Hz tone) and a deviant stimulus (1000 Hz tone) under passive and attentive listening conditions, respectively. Frequency discrimination ability was also performed using a standard psychoacoustic procedure. The 5-item Speech, Spatial and Qualities of Hearing Scale (SSQ5) questionnaire was used to assess subjective hearing. A series of computerized cognitive tests were administered to assess memory, attention, and executive function.

Results:
Compared to the Y group, the O group showed a larger amplitude and shorter latency in the peak components of the LAEP, smaller amplitudes, and longer latencies in the MMN, P3a, and P3b. In addition, the O group had poorer cognitive function (memory, attention, executive function) and expended more listening effort in daily life (SSQ question 5) compared to the Y group. Despite these group differences, the O group performed similarly in frequency discrimination compared to the Y group.

Conclusion:
The ERP findings can be explained by the decline of top-down control over the bottom-up process in the O group. The current results suggested that aging-related decline in cognitive function constitutes an important impact of aging on the auditory system.