Effects of Sensorineural Hearing Loss on Robust Speech Coding

描述（申请人提供）：听力损失程度相似的人可能有不同的语音识别能力，这是诊断和治疗听力障碍的一个巨大挑战。先前的研究已经确定，常见的听力损失是由内部和外部毛细胞损伤引起的。内部毛细胞和外部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，即内部和外部毛细胞功能障碍程度的差异导致了患者之间语言感知的差异。最近的心理物理学研究表明，感觉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下降。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争论，并可能对提高助听器和人工耳蜗在噪音中恢复语言感知的能力具有重要意义。所提出的神经生理学实验将通过直接量化感音神经丧失对听神经时间编码的影响，提供有价值的数据。将使用耳毒性药物研究选择性内或外毛细胞损伤的影响。噪声性听力损失将用于研究更常见的混合性毛细胞损伤。组织病理学分析和功能反应措施将用于表征单个动物的毛细胞病变。具体目标1是量化选择性毛细胞损伤对纤维内和纤维间时间编码的影响。创新的分析避免了以往跨光纤时间编码研究中的实验限制，将用于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，即感觉神经损失对精细结构的纤维间编码的影响大于纤维内编码。具体目的2是确定感觉神经丧失是否影响语音编码中精细结构和包络线索的神经编码。听力正常和受损的听者在理解语音编码的能力上存在差异，这表明他们在使用TFS线索时存在感知缺陷。这些感知结果的生理基础很难评估，因为窄带耳蜗过滤限制了在耳蜗输出处分离精细结构和包膜的能力。神经相互关系数将直接量化感音神经损失对噪声中语音编码精细结构和包络编码保真度的影响。模型支持在精细结构和包络响应中都发生显著退化的假设。具体目标3是量化感觉神经损失对并发复杂音调基频时间编码的影响。听力受损的听众利用音高差异来区分两个相互竞争的说话者的能力下降。据推测，估计两个并发复杂音调的基频的能力下降主要是由于时间精细结构的丧失，而不是由于未解析谐波的包络编码的退化。

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.