Individual differences in supra-threshold sound encoding

描述（由申请人提供）：一个长期存在的难题是，为什么听力正常的听众在其他听觉任务中表现出如此巨大的差异。当任务涉及分离多个声源时，例如当听众必须依赖选择性听觉注意时，“正常听力”听众之间的差异特别明显。最近的动物研究表明，噪声暴露可以损害听觉神经纤维的突触功效，而不会永久改变听力阈值，产生听神经病。低自发率的听觉神经纤维，这是特别重要的编码的时间内容的阈上声音，可能会优先受到影响。与动物研究相一致，我们的初步结果表明，在正常阈值的听众之间的选择性注意任务的表现差异与心理物理和生理措施，旨在揭示在阈上水平的时间编码的保真度。我们假设听神经病可能比以前认识到的更常见：听力正常的年轻听众可能在听觉神经纤维编码阈上时间信息的保真度上有所不同，从而影响他们在日常环境中的沟通能力。声音暴露会导致动物阈上缺陷，而没有阈值偏移;因此，我们还假设， 常规定义的噪声暴露导致的听力损失也可能遭受阈上缺陷，这实质上导致了交流困难。这个项目的主要目标是量化一群年轻的“正常听力”听众的听神经病。我们还将探讨如何阈上编码有助于提高阈值，由于噪声暴露的听众的性能差异。我们将：目的1）表征听觉通路皮层下部分阈上声音编码的个体差异;目的2）表征选择性注意能力的个体差异，并将其与 编码保真度的差异;和目标3）表征超阈值声音编码保真度如何有助于轻度至中度高频听力损失的收听者的性能差异。我们将比较生理（脑干反应，畸变产物耳声发射和皮层反应）和行为措施，从相同的听众和使用计算模型来解开这些指标之间的关系。我们的研究结果将量化阈上声音的外周编码在正常和升高阈值的听众之间的差异，并将确定阈上差异如何影响在常见社交环境中的沟通能力。我们的研究结果可能会导致临床 超阈值听力保真度测试，量化导致具有相似听力图的听众之间的沟通能力差异的一个因素。

DESCRIPTION (provided by applicant): A long-standing puzzle is why listeners with normal hearing thresholds show such enormous variation in performance on other auditory tasks. Differences among "normal hearing" listeners are particularly pronounced when tasks involve separating multiple sound sources, such as when listeners must rely on selective auditory attention. Recent animal work shows that noise exposure can damage the synaptic efficacy of auditory nerve fibers without permanently altering hearing thresholds, producing auditory neuropathy. Low-spontaneous rate auditory nerve fibers, which are especially important for encoding the temporal content of supra-threshold sound, may be preferentially affected. Consistent with animal studies, our preliminary results in listeners with normal thresholds suggest that inter-subject performance differences on selective attention tasks correlate with psychophysical and physiological measures designed to reveal the fidelity of temporal coding at supra-threshold levels. We hypothesize that auditory neuropathy may be much more common than previously recognized: young listeners with normal hearing thresholds may differ in the fidelity with which their auditory nerve fibers encode supra-threshold temporal information, affecting their ability to communicate in everyday settings. Sound exposure leads to supra-threshold deficits in animals without threshold shifts; thus, we also postulate that listeners with conventionally defined hearing loss from noise exposure likely also suffer from supra-threshold deficits that contribute substantially to communication difficulties. The main objective of this project is to quantify auditory neuropathy in a cohort of young, "normal hearing" listeners. We will also explore how supra-threshold encoding contributes to performance differences in listeners with elevated thresholds due to noise exposure. We will: Aim 1) characterize individual differences in supra-threshold sound encoding in subcortical portions of the auditory pathway; Aim 2) characterize individual differences in the ability to selectively attend, and relate them to differences in coding fidelity; and Aim 3) characterize how supra-threshold sound encoding fidelity contributes to performance differences for listeners with mild to moderate high-frequency hearing loss. We will compare physiological (brainstem responses, distortion product otoacoustic emissions, and cortical responses) and behavioral measures from the same listeners and use computational models to unravel the relationships between these metrics. Our results will quantify how peripheral encoding of supra-threshold sound differs across listeners with both normal and elevated thresholds, and will establish how supra-threshold differences affect the ability to communication in common social settings. Our results could lead to a clinical test of supra-threshold hearing fidelity, quantifying one factor leading to differences in communication ability amongst listeners with similar audiograms.