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

最近在动物身上的研究表明，暴露在噪声环境中导致听觉阈值的暂时性变化可以 导致耳蜗内毛细胞之间的突触连接受到永久性的严重损害 和听神经。如果这种“听觉性突触”发生在人类身上，就不会被电流检测到 标准的听力测试，但可以潜在地解释为什么许多人抱怨说 在嘈杂的背景下理解语言，尽管听力临床正常。这个项目的目标是 是确定听觉突触是否发生在人类身上，如果是的话，开发临床上可行的测试 来诊断它，以及研究它的感知后果的研究工具。该项目确定了三个 被认为可能患有听觉性突触的人群：1)患有 噪声暴露后出现耳鸣，但临床听力正常(即正常听力阈值) 在250至8000赫兹之间)；2)报告有接触过大声音的历史，但有 临床听力正常；3)高频(&gt；2 khz)有轻度至中度听力损失的人，但 临床上低频听力正常。这三个小组的结果将与来自 年龄和性别匹配的对照组，听力正常，没有耳鸣或过度耳鸣的报告 噪音暴露。该项目有三管齐下的方法，涉及生理、感知和言语- 基于标准的措施。第一个目的是研究突触对两种听觉反射的潜在影响： 中耳肌肉反射(MEMR)和内侧橄榄耳蜗肌反射(MOCR)。试点数据表明， 与之前的动物研究一致，听觉性突触病患者的MEMR严重减少。这个 第二个目的是通过测量对基本信息的敏感性来研究突触的潜在知觉后果 具有和不具有背景噪声的声学属性，如幅度和频率调制。试点数据 提示可能患有听觉突触的人特别容易受到噪音的影响，甚至 如果他们安静时的表现是正常的。第三个目的是研究不同背景下的言语感知 情况，包括噪声和语音干扰，有和没有增加混响。实验测试 这一预测认为，突触功能将受到影响，尤其是在大脑中 背景噪声是可变的和不可预测的，以及目标和干扰语音的位置 只能通过基频或空间位置上的微小差异来区分。结果来自于 该项目将提供重要的新信息和对潜在影响的疾病进行临床相关测试 美国和世界各地数以百万计的人。听性突触的可靠指标和诊断 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.