Auditory Cortical Processing in Hearing Loss

项目总结 拟议的实验旨在确定非对称性听力损失(AHL)的后果 在听觉皮质中影响允许听者分析和解码前景声音的神经过程 背景噪音。急性淋巴细胞性耳聋是最常见的听力障碍之一，它深刻地破坏了 空间听力和在噪声中处理信号的能力(正弦)。跨听力领域的残疾是 AHL患者通常比同等的对称性感音神经性耳聋患者更严重 (SNHL)。因此，急性淋巴细胞性白血病对健康有广泛的影响，包括耳鸣、认知障碍和减少 生活质量。我们最近发现，听觉的同侧和对侧的皮质半球 不对称声损伤后损失恢复不同。具体地说，声音的频谱首选项 AHL后约6个月内双耳在对侧大脑半球重新对齐，但仍存在 同侧大脑半球未对齐。无论是动态的还是功能上的后果 在SIN处理或中枢增益适应等关键听觉功能上的半球差异 为人所知。此外，我们最近发现，正常听觉皮质中的神经元在 它们对背景噪音的容忍程度。一些神经元实际上在存在的情况下改善了它们的处理 噪音。这种多样性创造了一个机会来确定决定大脑皮质对噪声的耐受性的因素 神经元和急性淋巴细胞性白血病的后果。 我们建议对以下的双侧皮质重组进行多方面的纵向分析 AHL。抑制性中间神经元的作用特别令人感兴趣，因为抑制性失调一直是 作为听力损失的原因和后果而牵连的。我们的目标将决定(1)AHL如何影响 皮层回路对背景声音的敏感性，(2)AHL如何影响皮质神经元的能力 适应刺激水平和对比度的变化，以及(3)AHL的功能变化与结构的关系 以及大脑皮层网络中抑制的功能表达。我们将估计频谱和时间调谐 属性、兴奋性-抑制性平衡和时间背景能力，这些都是优化 言语感知。我们将提供AHL中皮层SIN处理中断的第一次检查 研究在一系列相互竞争的背景噪声水平上的单声道和双声道信号解码能力。 我们将在神经解剖学上将急性髓系白血病引起的功能加工改变的程度和时间进程联系起来。 确定了两个大脑半球核心皮质区域间神经元密度的变化。财富 这一方法产生的新见解将解决许多悬而未决的问题 AHL及其动态时间进程的重组，为临床研究人员提供新的和更明确的 AHL的中央生物标志物，促进改进康复策略的发展，并提供新的 了解大脑如何在听力正常和受损时从噪音中提取信号的方法。

PROJECT SUMMARY The proposed experiments aim to determine how the consequences of asymmetric hearing loss (AHL) in auditory cortex affect the neural processes that allow listeners to parse and decode foreground sounds in background noise. AHL is one of the most common forms of hearing impairment, and it profoundly disrupts spatial hearing and the ability to process signals in noise (SIN). Disabilities across hearing domains are generally more severe in AHL patients than in equivalent cases of symmetric sensorineural hearing loss (SNHL). Thus, AHL has broad implications for health, including tinnitus, cognitive impairment, and reduced quality of life. We recently discovered that the cortical hemispheres ipsilateral and contralateral to the hearing loss recover differently after asymmetric acoustic trauma. Specifically, spectral preferences for sounds emanating from the two ears realign in the contralateral hemisphere within ~6 months after AHL but remain misaligned in the ipsilateral hemisphere. Neither the dynamics nor the functional consequences of these hemispheric differences on SIN processing or crucial auditory functions such as central gain adaptation are known. Furthermore, we recently discovered that neurons in normal auditory cortex are considerably diverse in how well they tolerate background noise. Some neurons actually improving their processing in the presence of noise. This diversity creates an opportunity to identify the factors that determine the noise tolerance of cortical neurons and the consequences of AHL. We propose to conduct a multifaceted, longitudinal analysis of bilateral cortical reorganization following AHL. The role of inhibitory interneurons is of special interest because inhibitory dysregulation has been implicated as both a cause and consequence of hearing loss. Our Aims will determine (1) how AHL affects the sensitivity to background sounds in the cortical circuits, (2) how AHL affects the ability of cortical neurons to adapt to changes in stimulus level and contrast, and (3) how functional changes in AHL relate to the structural and functional expression of inhibition in cortical networks. We will estimate spectral and temporal tuning properties, excitatory-inhibitory balance, and temporal context capabilities, which are all critical for optimal speech perception. We will provide the first examination of disrupted cortical SIN processing in AHL by studying monaural and binaural signal decoding abilities over a range of competing background noise levels. We will relate the degree and time course of AHL-induced functional processing changes to neuroanatomically determined alterations in the interneuron density across core cortical fields in the two hemispheres. The wealth of new insights generated by this approach will resolve numerous outstanding questions regarding central reorganization in AHL and its dynamic time course, equip clinical researchers with new and better-defined central biomarkers of AHL, facilitate the development of improved rehabilitation strategies, and provide a new way to understand how the brain extracts signals from noise in normal and impaired hearing.