Temporal Resolution of Cochlear and Auditory Nerve Responses in Older Adults

描述（由申请人提供）：老化损害听者处理时间复杂的声学刺激（如语音）的能力。这种时间处理能力下降的来源包括中枢听觉神经系统中与年龄相关的变化。外周听觉系统内的听觉神经纤维活动也随着年龄的增长而变得更加异步。此外，许多老年人患有耳蜗听力损失，这可能通过降低耳蜗非线性而有效地限制时间处理能力。本研究的长期目标是确定衰老引起的言语理解缺陷的听觉基础。本申请的目的是确定在何种程度上的异常感知随时间变化的语音线索的结果与年龄有关的变化或之前的水平的听觉神经。核心假设是，老化改变了耳蜗的机械和听觉神经反应，从而干扰了理解语言的能力。这一假设是基于证据表明，非线性耳蜗反应和同步神经反应参与编码的时间语音功能。评估周边（耳蜗机械和听觉神经）的时间处理在老年人是必要的，因为它是不知道周边的时间赤字有助于异常感知的时间言语线索。该方法是测量生理反应，修改最近发布的用于评估时间分辨率和基底膜压缩的心理物理技术。这些措施，然后将进行比较，在同一组的老年人和年轻人正常或听力受损的时间言语任务的性能。具体目标1将基于使用前向掩蔽范例获得的听觉神经复合动作电位（CAP）测量时间分辨率。特定目标2将根据刺激频率耳声发射（SFOAE）估计耳蜗机械压缩和传播时间。SFOAE和CAP反应的比较将确定在老年人的听觉系统中外毛细胞功能改变听觉神经反应的幅度和时间的程度。具体目标3将确定时间言语任务的表现是否取决于耳蜗机械和听觉神经反应。这项工作的基本原理是，一旦减少时间处理的来源是已知的，助听器的装配和康复训练策略可以设计，补救个别患者的时间处理问题。所提出的生理测量不受认知或记忆中与年龄相关的变化的干扰。因此，这项研究具有额外的意义，因为它可能导致临床工具的开发，这些工具将针对减少时间处理的来源。

DESCRIPTION (provided by applicant): Aging impairs the ability of listeners to process temporally complex acoustic stimuli, such as speech. Sources of this decline in temporal processing ability include age-related changes in the central auditory nervous system. Auditory nerve fiber activity within the peripheral auditory system also becomes more asynchronous with age. Furthermore, many older adults suffer from cochlear hearing loss, which may effectively limit temporal processing ability by reducing cochlear nonlinearity. The long-term goal of this research is to determine the auditory basis of speech understanding deficits imposed by aging. The objective of this application is to determine the extent to which abnormal perception of time-varying speech cues results from age-related changes at or before the level of the auditory nerve. The central hypothesis is that aging alters cochlear mechanical and auditory nerve responses, thereby interfering with the ability to understand speech. This hypothesis is based on evidence that nonlinear cochlear responses and synchronized neural responses are involved in the encoding of temporal speech features. Evaluation of peripheral (cochlear mechanical and auditory nerve) temporal processing in older adults is necessary because it is not known how peripheral timing deficits contribute to abnormal perception of temporal speech cues. The approach is to measure physiological responses, modifying recently-published psychophysical techniques used to assess temporal resolution and basilar membrane compression. These measures will then be compared to performance on temporal speech tasks in the same groups of elderly and young adults with normal or impaired hearing. Specific Aim 1 will measure temporal resolution based on auditory nerve compound action potentials (CAPs) obtained using a forward-masking paradigm. Specific Aim 2 will estimate cochlear mechanical compression and travel time from stimulus-frequency otoacoustic emissions (SFOAEs). Comparisons of SFOAE and CAP responses will determine the extent that the amplitude and timing of auditory nerve responses is altered by outer hair cell function in the auditory systems of older adults. Specific Aim 3 will determine whether performance on a temporal speech task depends on cochlear mechanical and auditory nerve responses. The rationale for this work is that once sources of reduced temporal processing are known, hearing aid fitting and rehabilitative training strategies can be devised that remediate the temporal processing problems of individual patients. Proposed physiological measures are free from confounding by age-related changes in cognition or memory. Therefore, this research has additional significance in that it may lead to development of clinical tools that will target sources of reduced temporal processing.