How aging impacts the encoding of binaural cues and the perception of auditory space

Abstract

Over the years, the effect of aging on auditory function has been investigated in animal models and humans in an effort to characterize age-related changes in both perception and physiology. Here, we review how aging may impact neural encoding and processing of binaural and spatial cues in human listeners with a focus on recent work by the authors as well as others. Age-related declines in monaural temporal processing, as estimated from measures of gap detection and temporal fine structure discrimination, have been associated with poorer performance on binaural tasks that require precise temporal processing. In lateralization and localization tasks, as well as in the detection of signals in noise, marked age-related changes have been demonstrated in both behavioral and electrophysiological measures and have been attributed to declines in neural synchrony and reduced central inhibition with advancing age. Evidence for such mechanisms, however, are influenced by the task (passive vs. attending) and the stimulus paradigm (e.g., static vs. continuous with dynamic change). That is, cortical auditory evoked potentials (CAEP) measured in response to static interaural time differences (ITDs) are larger in older versus younger listeners, consistent with reduced inhibition, while continuous stimuli with dynamic ITD changes lead to smaller responses in older compared to younger adults, suggestive of poorer neural synchrony. Additionally, the distribution of cortical activity is broader and less asymmetric in older than younger adults, consistent with the hemispheric asymmetry reduction in older adults model of cognitive aging. When older listeners attend to selected target locations in the free field, their CAEP components (N1, P2, P3) are again consistently smaller relative to younger listeners, and the reduced asymmetry in the distribution of cortical activity is maintained. As this research matures, proper neural biomarkers for changes in spatial hearing can provide objective evidence of impairment and targets for remediation. Future research should focus on the development and evaluation of effective approaches for remediating these spatial processing deficits associated with aging and hearing loss.

Auditory motion tracking ability of adults with normal hearing and with bilateral cochlear implants

“…Aging effects have also been reported for binaural sensitivity measures, but more so for sensitivity to ITD than to ILD (e.g., Babkoff et al, 2002), thus, to the extent that listeners relied on ILDs to solve the task, older listeners may have had a disadvantage compared with younger listeners. Some insight can also be gleaned from studies showing aging effects on electrophysiological measures related to processing of spatial cues (Briley and Summerfield, 2014;Ozmeral et al, 2016; for a comprehensive review, see Eddins et al, 2018). On a more global functional scale, aging has been associated with a decline in a number of factors that might have contributed to the tasks in the present study.…”

Speech-in-Noise Recognition With More Realistic Implementations of a Binaural Cochlear-Implant Sound Coding Strategy Inspired by the Medial Olivocochlear Reflex

“…This is unlikely problematic because all participants were able to perform the task and the study explored within-subject effects only (the main factors were processing strategy and spatial configuration). In other words, if any factor had made children perform differently from adults (e.g., Dubno et al 2008 ; Eddins et al 2018 ), the factor(s) in question would have affected all processing strategies equally.…”

Evaluating the Impact of Age, Acoustic Exposure, and Electrical Stimulation on Binaural Sensitivity in Adult Bilateral Cochlear Implant Patients

“…Aging during adulthood can also play a role in binaural sensitivity, as seen in human studies conducted with older adults. Both behavioral and electrophysiological measures have shown that aging leads to declines in the ability to process binaural cues including ITDs and interaural phase differences (IPDs) in individuals with normal audiometric thresholds [ 17 , 18 ]. Behavioral measures with older listeners have shown that ITD thresholds measured using a 100-Hz acoustic pulse train are typically double that of younger listeners, particularly at very low sensation levels [ 19 , 20 , 21 ].…”

“…Electrophysiological measures have been used in prior studies to understand the physiological correlates of sensitivity to interaural differences in older and younger listeners, specifically for ITDs. For example, cortical responses to ITDs differ in older (mean = 70.0 years) versus younger (mean = 24.9 years) listeners [ 17 ]. In older adults, larger cortical auditory evoked potential magnitudes are measured in response to static ITDs compared to younger listeners.…”

“…In older adults, larger cortical auditory evoked potential magnitudes are measured in response to static ITDs compared to younger listeners. Conversely, significantly longer latencies with smaller magnitudes for the first negative peak (N1) and second positive peak (P2) are observed for older versus younger listeners when a dynamically changing ITD is presented to listeners, suggesting poorer neural synchrony [ 17 , 24 ]. Additional work has found that the ability to use interaural temporal information to aid in the release from masking (e.g., binaural masking level differences; BMLDs) also declines with increasing age [ 19 ].…”