Effects of noise-induced and metabolic hearing losses on temporal coding in noise

描述（由申请人提供）：听力损失的人在嘈杂的环境中通常很难理解言语，即使有助听器的帮助。知觉研究表明，赤字的时间处理迅速变化的精细结构是负责。然而，动物的神经生理学研究一般没有发现时间处理的缺陷。因此，语音清晰度差的基础仍然不清楚。然而，现有的神经生理学研究是有限的，因为它们测量了安静条件下的时间处理，并且主要检查了一种常见的听力损失形式（噪声引起的）。此外，这些研究没有检查宽带刺激的时间响应的频率调谐。所提出的对龙猫听觉神经纤维反应的神经生理学研究通过以下方式解决了这些限制：（1）量化背景噪声中的时间处理，当前助听器经常失败，（2）检查两种形式的听力损失，以及（3）量化时间反应的频率调谐。目标1使用声学过度暴露来研究噪声性听力损失（NIHL），而目标2使用呋塞米注射来研究代谢性听力损失（MHL;呋塞米注射模拟这种常见形式的年龄相关性听力损失，结果良好）。声学刺激将包括纯音和调幅音。时间处理将使用经典的矢量强度和新的相关指数计算洗牌相关图进行量化。最后，目标3将采用维纳核分析的时间响应白色噪声研究频率调谐的时间处理在动物与NIHL和MHL。实验的结果将被用来测试三个假设。首先，听力损失预计会导致在背景噪声中的时间处理的缺陷。该假设基于信号处理模型，其预测在听觉滤波器带宽增加之后背景噪声对信号响应的更强影响（即，在处理任务期间更多噪声能量进入滤波器，从而增加掩蔽）。第二，基于听觉感知的相关研究，听力损失对时间精细结构的影响要大于对幅度包络的影响。最后，对于给定程度的听力损失，NIHL预计会导致更大的赤字在噪声中的时间处理比MHL。这一假设是基于先前在NIHL研究中观察到的具有超敏感尾部的调谐曲线，而不是MHL。在信号处理过程中，超敏感的尾部应该允许更多的噪声能量进入，从而在更大程度上降低时间编码。拟议的研究将推进我们对与两种常见形式的听力损失相关的听觉处理缺陷的认识。这项研究和其他研究确定的具体缺陷可用于指导新技术的开发（例如助听器和耳蜗植入设计），旨在恢复听力损失患者在真实世界听力条件下的言语感知。

DESCRIPTION (provided by applicant): People with hearing loss often have great difficulty understanding speech in noisy environments, even with assistance from a hearing aid. Perceptual studies suggest that a deficit in temporal processing of rapidly varying fine structure is responsible. However, neurophysiological studies in animals have generally not found a deficit in temporal processing. Hence, the basis for poor speech intelligibility remains unclear. The existing neurophysiological studies are limited, however, because they measured temporal processing under quiet conditions and primarily examined only one commonly occurring form of hearing loss (noise- induced). Furthermore, these studies did not examine the frequency tuning of temporal responses to broadband stimuli. The proposed neurophysiological study of auditory nerve fiber responses in chinchillas resolves these limitations by (1) quantifying temporal processing in background noise, where current hearing aids often fail, (2) examining two forms of hearing loss, and (3) quantifying the frequency tuning of temporal responses. Aim 1 uses acoustic overexposures to study noise-induced hearing loss (NIHL), while Aim 2 uses furosemide injections to study metabolic hearing loss (MHL; furosemide injections simulate this common form of age-related hearing loss with good results). Acoustic stimuli will include pure tones and amplitude modulated tones. Temporal processing will be quantified using classical vector strength and novel correlation indices computed from shuffled correlograms. Finally, Aim 3 will employ Wiener kernel analyses of temporal responses to white noise to study the frequency tuning of temporal processing in animals with NIHL an MHL. The results of the proposed experiments will be used to test three hypotheses. First, hearing loss is expected to result in a deficit in temporal processing in background noise. This hypothesis is based on models of signal processing, which predict a stronger effect of background noise on the response to a signal following an increase in auditory filter bandwidth (i.e. more noise energy enters the filter during the processing task, thereby increasing masking). Second, based on the related studies of auditory perception, hearing loss should degrade processing of temporal fine structure more than the amplitude envelope. Finally, for a given degree of hearing loss, NIHL is expected to result in a greater deficit in temporal processing in noise than MHL. This hypothesis is based on previous observations of tuning curves with hypersensitive tails in studies of NIHL, but not MHL. The hypersensitive tails should allow more noise energy to enter during signal processing, thereby degrading temporal coding to a greater degree. The proposed research will advance our knowledge of the deficits in auditory processing associated with two common forms of hearing loss. The specific deficits identified by this and other studies can be used to guide the development of new technologies (e.g. hearing-aid and cochlear-implant designs) aimed at restoring speech perception under real-world listening conditions in people with hearing loss.