Neural Pathophysiology and Suprathreshold Processing in Young Adults with Normal Thresholds

项目3摘要-摘要 我们实验室最近的动物研究表明，毛细胞和 耳蜗神经末梢是内耳中最脆弱的元件， 老年性听力损失这种突触变性不影响毛细胞或阈值， 因此隐藏在正常听力图的后面。然而，这种“隐性听力损失”可能有助于 理解言语的能力下降，尤其是在嘈杂的环境中。它也可能是一个潜在的 耳鸣和听觉过敏的原因。对于动物来说，隐性听力损失可以通过测量 ABR波I的阈上振幅，耳蜗神经的声诱发活动。 我们已经开始将这些见解从动物研究转化为人类研究。我们有飞行员 对听力正常年轻人的研究显示， 耳蜗电图测量与耳蜗突触病一致， 语音识别任务。 在这里，我们建议将我们的试点研究扩展到大规模的横截面（目标1）和纵向 (Aim 2）听力正常大学生隐性听力损失的研究， 通过问卷调查量化，在听觉虐待方面存在广泛差异的生活方式。目标1： 测试隐藏的听力损失的假设，定义为困难词的表现缺陷， 识别任务，与耳蜗突触病一致的生理反应缺陷相关 以及估计的寿命噪声剂量。我们的结果将是噪音测试。一 统计模型将测试这些结果与噪声暴露史和 一系列生理或心理物理测量，用于探测听觉的不同阶段 处理，即畸变产物耳声发射和高频测听，SP/AP比 以及对高调制频率的音调的响应后的包络，中耳肌肉或 内侧橄榄耳蜗反射，频率的几个变种以下的反应探测单耳和 双耳时间精细结构加工，随机理论的时间整合测试 耳蜗突触病、耳鸣严重程度/障碍和响度不适的采样不足 水平/听觉过敏。使用主成分分析，聚类分析和自适应LASSO，我们将 找到最能预测结果的测试组合，并评估相对贡献 外周与中枢病理生理学对所观察到的性能缺陷的影响。在目标2中，我们将测试 假设年轻人在定期和持续的声学检查中会发生隐性听力损失 通过跟踪一批学生在这个项目的五年期间使用相同的 如目标2所述测试电池。

Project 3 Summary – Abstract Recent animal work from our laboratories suggests that the synapses between hair cells and cochlear nerve terminals are the most vulnerable elements of the inner ear in both noise-induced and age-related hearing loss. This synaptic degeneration does not affect hair cells or thresholds and, therefore, hides behind a normal audiogram. However, this “hidden hearing loss” likely contributes to decreased ability to understand speech, especially in noisy environments. It may also be an underlying cause of tinnitus and hyperacusis. In animals, hidden hearing loss can be diagnosed by measuring the suprathreshold amplitude of ABR wave I, the sound-evoked activity of the cochlear nerve. We have begun translating these insights from animal work to human studies. We have a pilot study from audiometrically normal young adults showing significant correlations between electrocochleographic measures consistent with cochlear synaptopathy and performance on difficult speech recognition tasks. Here we propose to extend our pilot study into large-scale cross-sectional (Aim 1) and longitudinal (Aim 2) studies of hidden hearing loss in college students with normal audiometric thresholds and widely differing lifestyle with respect to aural abuse, as quantified by questionnaire. For Aim 1, we will test the hypotheses that hidden hearing loss, defined as performance deficits on difficult word- recognition tasks, is correlated with physiologic response deficits consistent with cochlear synaptopathy and with estimated lifetime noise dose. Our outcome measures will be speech-in-noise tests. A statistical model will test the correlation of these outcomes with noise-exposure history and with a battery of physiological or psychophysical measures chosen to probe different stages of auditory processing, i.e. distortion product otoacoustic emissions and high-frequency audiometry, SP/AP ratio and envelope following responses to tones at high modulation frequencies, middle ear muscle or medial olivocochlear reflexes, several variants of frequency following response probing monaural and binaural temporal fine-structure processing, a temporal integration test of theories on stochastic undersampling in cochlear synaptopathy, and tinnitus severity/handicap and loudness discomfort level/hyperacusis. Using principal components analysis, cluster analysis and adaptive LASSO, we will find the test combination that best predicts the outcome measures and assess the relative contributions of peripheral vs. central pathophysiology to the observed performance deficits. In Aim 2, we will test the hypothesis that hidden hearing loss progresses in young adults with regular and continued acoustic overexposure by tracking a cohort of students over the five-year period of this project using the same test battery as described in Aim 2.