Hearing Deficit Due to Auditory Neuropathy

描述（由申请人提供）：本提案将研究一种最近被认可的听力障碍形式，称为听神经病变（AN），这是由于听神经功能障碍而存在正常的耳蜗受体活动。AN受试者耳蜗外毛细胞活动测量正常，但从听神经开始的中枢听觉通路功能测量异常。听力障碍对语言理解的影响与纯音丧失的影响不成比例，尤其是在噪声环境下的语音识别。AN并不罕见，占新生儿听力损失的10%，在儿童和成人中也会发生。成人听神经障碍常伴有周围神经病变。此外，AN和感觉性听力损失同时发生。神经同步性丧失和听神经输入减少被认为是听力障碍的主要机制。最近发现听神经异常部位位于听神经节细胞及其轴突（I型AN）或远端位于听外周，在那里听神经末梢、内毛细胞和内毛细胞与神经末梢之间的突触非常接近（II型AN）。我们的长期目标是了解AN的潜在机制和伴随的听力损害，为减轻AN受试者的听力缺陷提供科学依据。我们提出了四个实验，使用心理物理和电生理技术，将帮助我们实现这些目标。我们将描述(1)中枢听觉通路的重组发生在听神经输入改变的反应中；(2)失同步和听觉输入减少是AN的病理生理机制；(3)人工耳蜗植入AN受试者听觉颞叶过程改善的客观生理和心理物理测量；(4)利用新的听觉处理技术改善语音识别。我们的研究结果可能对听神经病变的诊断、分类、认识和治疗有重要影响。

DESCRIPTION (provided by applicant): This proposal will study a recently recognized form of hearing disorder called auditory neuropathy (AN) that is due to a disorder of auditory nerve functions in the presence of normal cochlear receptor activities. AN subjects have normal measures of cochlear outer hair cell activities but abnormal measures of the central auditory pathway functions beginning with auditory nerve. The hearing disorder typically affects speech comprehension out-of-proportion to the pure tone loss, particularly speech recognition in noise. AN is not rare and accounts for 10 percent of newborns identified as having hearing loss and also develops in childhood and in adults. In adults the disorder of auditory nerve is commonly associated with a peripheral neuropathy. In addition, AN and sensory hearing loss occur together. Loss of neural synchrony and decreased auditory nerve input are proposed as cardinal mechanisms underlying the hearing disorder. The sites of abnormality along auditory nerve have recently been identified at auditory ganglion cells and their axons (Type I AN) or distally in the auditory periphery where auditory nerve terminals, inner hair cells, and the synapses between inner hair cells with nerve terminals are in close approximation (Type II AN). Our long-term goals are to understand the underlying mechanisms of AN and the accompanying hearing impairments to provide a scientific basis for alleviating the hearing deficit in AN subjects. We propose four experiments using both psychophysical and electrophysiological techniques that will help us achieve these goals. We will characterize (1) the reorganization of central auditory pathway occurring in response to altered auditory nerve input; (2) the contributions of dysynchronization and decreased auditory input as pathophysiological mechanisms underlying AN; (3) the objective physiological and psychophysical measures of improved auditory temporal processes in cochlear implanted AN subjects, and (4) the improvement of speech recognition using new auditory processing techniques. The results of our studies could have major impact on the diagnosis, classification, understanding, and treatment of auditory neuropathy.