Department of Communication Sciences and Disorders, University of South Florida, USA.
Department of Communication Sciences and Disorders, University of South Florida, USA.
Hear Res. 2018 Nov;369:79-89. doi: 10.1016/j.heares.2018.05.001. Epub 2018 May 5.
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.
多年来，人们一直在动物模型和人类中研究衰老对听觉功能的影响，以描述感知和生理方面与年龄相关的变化。在这里，我们回顾了衰老如何影响人类听力者对双耳和空间线索的神经编码和处理，重点介绍了作者及其他研究人员的最新研究成果。从检测间隙和时间精细结构辨别能力的测量结果来看，与双耳任务所需的精确时间处理相关的单耳时间处理随年龄的下降，与较差的双耳任务表现相关。在侧化和定位任务中，以及在噪声中的信号检测中，行为和电生理测量都显示出与年龄相关的显著变化，并归因于随年龄增长而出现的神经同步性下降和中枢抑制减少。然而，这些机制的证据受到任务（被动与注意）和刺激范式（例如，静态与连续与动态变化）的影响。也就是说，与年轻人相比，老年人对静态的两耳时间差（ITD）的听觉皮层诱发电位（CAEP）较大，这与抑制减少有关，而对于具有动态 ITD 变化的连续刺激，老年人的反应较小，表明神经同步性较差。此外，与年轻人相比，老年人的皮质活动分布较宽且不对称性较小，这与认知老化的老年人半球不对称性减少模型一致。当老年听众关注自由场中选定的目标位置时，他们的 CAEP 成分（N1、P2、P3）相对于年轻听众再次变小，皮质活动分布的不对称性减小保持不变。随着这项研究的成熟，空间听力变化的适当神经生物标志物可以提供损伤的客观证据，并为矫正提供目标。未来的研究应集中于开发和评估有效方法，以矫正与衰老和听力损失相关的这些空间处理缺陷。
