Physiological measures and perceptual consequences of noise-induced auditory synaptopathy in humans.

最近对动物的研究表明，噪声暴露导致听觉阈值暂时性变化， 导致耳蜗内毛细胞之间突触连接的永久性和严重损伤 和听觉神经。如果这种“听觉突触病”发生在人类身上， 标准的听力测试，但可能解释为什么许多人抱怨过度困难， 在嘈杂的背景下理解语音，尽管临床上听力正常。这个项目的目标 是确定人类是否会发生听觉突触病，如果是的话， 来诊断它沿着研究工具来研究它的感知后果。该项目确定了三个 被认为是潜在的听觉突触病患者的人群：1）患有 噪声暴露后的耳鸣，但具有临床正常听力的人（即，正常测听阈 在250和8000 Hz之间）; 2）报告有暴露于响亮声音的历史，但 临床听力正常; 3）在高频（> 2 kHz）下有轻度至中度听力损失，但 临床上正常的低频听力。这三组的结果将与 年龄和性别匹配的对照组听力正常，没有报告耳鸣或过度耳鸣。 噪声暴露该项目有一个三管齐下的方法，涉及生理，感知和语音- 基础措施。第一个目的是研究突触病对两种听觉反射的潜在影响： 中耳肌反射（MEMR）和内侧橄榄耳蜗反射（MOCR）。试点数据显示， 与先前的动物研究一致，听觉突触病患者的MEMR严重降低。的 第二个目的是通过测量对基本神经元的敏感性来研究突触病的潜在感知后果。 声学属性，例如振幅和频率调制，有或没有背景噪声。导频数据 这表明，潜在的听觉突触病患者特别容易受到噪音的影响， 如果他们在安静时的表现是正常的话。第三个目的是研究在多种背景下的言语知觉 环境，包括噪音和语音干扰，有和没有增加混响。实验测试 预测表现将受到突触病的影响，特别是在神经元的水平 背景噪声是可变的和不可预测的，并且目标和干扰语音 仅通过基频或空间位置的微小差异来区分。的结果 该项目将提供重要的新信息和临床相关的测试条件，可能影响 在美国和世界各地的数百万人。听觉突触病的可靠指标和诊断 人类将在开发治疗这种疾病的新药物方面发挥关键作用。

Recent studies in animals have shown that noise exposure causing temporary shifts in auditory thresholds can lead to permanent and severe damage to the synaptic connections between the inner hair cells in the cochlea and the auditory nerve. If such “auditory synaptopathy” occurs in humans, it would not be detected by current standard audiometric tests, but could potentially explain why many people complain of excessive difficulty in understanding speech in noisy backgrounds, despite having clinically normal hearing. The goal of this project is to determine whether auditory synaptopathy occurs in humans and, if so, to develop clinically feasible tests to diagnose it along with research tools to study its perceptual consequences. The project identifies three populations who are considered to be potential suffers of auditory synaptopathy: 1) People who suffer from tinnitus following noise exposure, but who have clinically normal hearing (i.e., normal audiometric thresholds between 250 and 8000 Hz); 2) People who report having a history of exposure to loud sound, but have clinically normal hearing; 3) People with mild-to-moderate hearing loss at high frequencies (> 2 kHz) but clinically normal hearing at low frequencies. Results from these three groups will be compared with those from an age- and gender-matched control group of people with normal hearing and no reported tinnitus or excessive noise exposure. The project has a three-pronged approach, involving physiological, perceptual, and speech- based measures. The first aim studies the potential effects of synaptopathy on two auditory reflexes: the middle ear muscle reflex (MEMR) and the medial olivocochlear reflex (MOCR). Pilot data suggest that potential sufferers of auditory synaptopathy have severely reduced MEMR, in line with previous animal studies. The second aim investigates potential perceptual consequences of synaptopathy by measuring sensitivity to basic acoustic attributes, such as amplitude and frequency modulation, with and without background noise. Pilot data suggest that potential suffers of auditory synaptopathy are particularly susceptible to the effects of noise, even if their performance in quiet is normal. The third aim studies speech perception in a variety of background situations, including noise and speech interference with and without added reverberation. The experiments test the prediction that performance will be affected by synaptopathy particularly in cases where the level of the background noise is variable and unpredictable, and where the target and interfering speech are distinguishable only by small differences in fundamental frequency or spatial location. The results from the project will provide important new information and clinically relevant tests of a condition that potentially affects millions of people in the US and worldwide. Reliable indicators and diagnoses of auditory synaptopathy in humans will be crucial in the development of new pharmaceutical treatments of the disorder.