Effects of Sensorineural Hearing Loss on Robust Speech Coding

描述（申请人提供）：诊断和治疗听力障碍的一个巨大挑战来自这样一个事实，即听力损失程度相似的人可能具有不同的语音识别能力。以前的研究已经确定，常见形式的听力损失是由内毛细胞和外毛细胞损伤的混合物引起的。内毛细胞和外毛细胞以根本不同的方式促进听力的概念框架激发了一般假设，即内毛细胞和外毛细胞功能障碍程度的差异导致了患者言语感知的差异。最近的心理物理学研究表明，感音神经性听力损失的听者在言语感知中使用时间精细结构线索的能力降低。这些研究引发了关于时间编码在正常和受损听力中的作用的积极辩论，并可能对提高助听器和人工耳蜗植入物在噪声中恢复言语感知的能力具有重要意义。所提出的神经生理学实验将提供有价值的数据，直接量化的感觉神经损失的影响，在听觉神经的时间编码。将使用耳毒性药物研究选择性内毛细胞或外毛细胞损伤的影响。噪声引起的听力损失将被用于研究更常见的混合毛细胞损伤的情况。将使用组织学分析和功能反应测量来表征个体动物的毛细胞病变。具体目标1是量化选择性毛细胞损伤对纤维内和跨纤维时间编码的影响。创新的分析，避免以前的实验限制在跨光纤时间编码的研究将被用来量化精细结构和包络编码，以及行波延迟。初步数据支持我们的假设，感觉神经损失影响跨纤维编码的精细结构比内纤维编码。具体目标2是确定是否感觉神经损失影响语音编码的精细结构和包络线索的神经编码。听力正常和受损的听众之间理解声码语音的能力差异已被用来表明在使用TFS线索的感知缺陷。这些感知结果的生理基础难以评估，因为窄带耳蜗滤波限制了在耳蜗的输出处隔离精细结构和包络的能力。神经互相关系数将直接量化噪声环境中感觉神经损失对声码语音精细结构和包络编码保真度的影响。建模支持的假设，即显着的退化发生在精细结构和包络响应。具体目标3是量化感觉神经损失对并发复杂音调中基频时间编码的影响。有听力损失的听众利用音高差异来区分两个竞争的谈话者的能力下降。假设估计两个并发复音调的基频的能力主要由于时间精细结构的损失而劣化，而不是来自未解析谐波的劣化包络编码。 公共卫生相关性：长期的目标，拟议的工作是获得一个更好的理解的生理基础，强大的语音感知，这具有重要的理论和临床意义。在拟议的实验中收集的数据将提供有关内耳损伤对感知相关声音的神经编码的差异影响的基础知识。这些知识将有助于制定诊断和康复策略，以改善听力损失患者的日常生活。

DESCRIPTION (provided by applicant): A great challenge in diagnosing and treating hearing impairment comes from the fact that people with similar degrees of hearing loss may have different speech recognition abilities. Previous research has established that common forms of hearing loss arise from a mixture of inner- and outer-hair-cell damage. A conceptual framework that inner and outer hair cells contribute to hearing in fundamentally different ways motivates the general hypothesis that differences in the degree of inner- and outer-hair-cell dysfunction contribute to across-patient variability in speech perception. Recent psychophysical studies have suggested that listeners with sensorineural hearing loss have a reduced ability to use temporal fine-structure cues in speech perception. These studies have fueled an active debate about the role of temporal coding in normal and impaired hearing, and may have important implications for improving the ability of hearing aids and cochlear implants to restore speech perception in noise. The proposed neurophysiological experiments will provide valuable data by directly quantifying the effects of sensorineural loss on temporal coding in the auditory nerve. The effects of selective inner- or outer-hair-cell damage will be studied using ototoxic drugs. Noise-induced hearing loss will be used to study the more common case of mixed hair-cell damage. Histopathological analyses and functional response measures will be used to characterize hair-cell lesions in individual animals. Specific Aim 1 is to quantify the effects of selective hair-cell damage on within- and across-fiber temporal coding. Innovative analyses that avoid previous experimental limitations in the study of across-fiber temporal coding will be used to quantify fine-structure and envelope coding, as well as traveling-wave delays. Preliminary data support our hypothesis that sensorineural loss affects across-fiber coding of fine-structure more than within-fiber coding. Specific Aim 2 is to determine whether sensorineural loss affects neural coding of fine-structure and envelope cues in vocoded speech. Differences in the ability to understand vocoded speech between listeners with normal and impaired hearing have been used to suggest a perceptual deficit in the use of TFS cues. The physiological basis for these perceptual results is difficult to evaluate because narrowband cochlear filtering limits the ability to isolate fine-structure and envelope at the output of the cochlea. Neural cross-correlation coefficients will quantify directly the effects of sensorineural loss on the fidelity of fine-structure and envelope coding for vocoded speech in noise. Modeling supports the hypothesis that significant degradations occur in both fine-structure and envelope responses. Specific Aim 3 is to quantify the effects of sensorineural loss on temporal coding of fundamental frequency in concurrent complex tones. Listeners with hearing loss show a reduced ability to make use of voice-pitch differences to segregate two competing talkers. It is hypothesized that the ability to estimate the fundamental frequencies of two concurrent complex tones is degraded primarily due to the loss of temporal fine structure, rather than from degraded envelope coding of unresolved harmonics. PUBLIC HEALTH RELEVANCE: The long-term goal of the proposed work is to obtain a better understanding of the physiological bases for robust speech perception, which has important theoretical and clinical implications. The data collected in the proposed experiments will provide fundamental knowledge about the differential effects of inner ear damage on the neural coding of perceptually relevant sounds. This knowledge will benefit the development of diagnostic and rehabilitative strategies to improve the daily lives of people with hearing loss.