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

描述(申请人提供)：听力损失的人在嘈杂的环境中往往很难听懂语言，即使有助听器的帮助。知觉研究表明，快速变化的精细结构在时间处理上的缺陷是原因之一。然而，动物的神经生理学研究通常没有发现时间加工的缺陷。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，因为他们测量了安静条件下的时间加工，并且主要只检查了一种常见的听力损失形式(噪声引起的)。此外，这些研究没有考察对宽带刺激的时间反应的频率调谐。拟议的龙猫听觉神经纤维反应的神经生理学研究通过(1)量化背景噪声中的时间处理，(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，解决了这些限制。Aim 1使用声过度暴露来研究噪声性听力损失(NIHL)，而Aim 2使用速尿注射来研究代谢性听力损失(MHL；速尿注射模拟这种常见的与年龄相关的听力损失，效果良好)。声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从混洗的相关图计算的新的相关指数来量化。最后，Aim 3将使用对白噪声的时间响应的Wiener核分析来研究患有NIHL和MHL的动物的时间处理的频率调谐。拟议中的实验结果将被用来检验三个假设。首先，听力损失预计会导致背景噪声中时间处理的缺陷。这一假设是基于信号处理模型的，该模型预测随着听觉过滤器带宽的增加(即在处理任务期间更多的噪声能量进入过滤器，从而增加掩蔽)，背景噪声对信号的响应会产生更强的影响。第二，基于听觉知觉的相关研究，听力损失对时间精细结构加工的影响大于对幅度包络的影响。最后，对于给定程度的听力损失，NIHL预计会导致比MHL更大的噪声时间处理缺陷。这一假设是基于之前在NIHL研究中观察到的带有超敏尾巴的调谐曲线，而不是MHL。超敏感的尾巴应该允许更多的噪声能量在信号处理期间进入，从而在更大程度上降低时间编码。这项拟议的研究将促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了解。这项研究和其他研究确定的具体缺陷可以用来指导新技术的发展(例如助听器和人工耳蜗设计)，旨在恢复听力损失人在现实世界听力条件下的言语感知。 公共卫生相关性：要实现听力损失患者提高语言清晰度的长期目标，需要详细了解与听力损失相关的听觉处理缺陷。拟议中的龙猫听觉神经纤维反应研究通过量化两种常见形式的听力损失对(1)在嘈杂的真实世界听力条件下的时间处理和(2)对宽带刺激的时间反应的影响来推进这一知识。这项拟议的研究和其他研究提供的详细知识将有助于指导新技术的发展，如助听器和旨在恢复听力损失人的言语感知的人工耳机设计。

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. PUBLIC HEALTH RELEVANCE: Achieving the long term goal of greater speech intelligibility in people with hearing loss will require a detailed knowledge of the deficits in auditory processing associated with hearing loss. The proposed study of auditory nerve fiber responses in chinchillas advances this knowledge by quantifying the effects of two common forms of hearing loss on (1) temporal processing under noisy, real-world listening conditions and (2) temporal responses to broadband stimuli. The detailed knowledge provided by the proposed study and others will help guide the development of new technologies such as hearing-aid and cochlear implant designs aimed at restoring speech perception in people with hearing loss.