Auditory Cortical Processing in Hearing Loss

项目摘要 拟议的实验旨在确定不对称听力损失（AHL）的后果如何 在听觉皮层影响神经过程，使听众解析和解码前景声音， 背景噪音AHL是最常见的听力障碍形式之一，它深刻地破坏了 空间听觉和在噪声中处理信号的能力（SIN）。听力障碍是 AHL患者的严重程度通常高于对称性感音神经性听力损失的同等病例 （SNHL）。因此，AHL对健康具有广泛的影响，包括耳鸣，认知障碍和减少 生活质量我们最近发现听觉同侧和对侧的大脑皮层 不对称声损伤后损失的恢复不同。具体来说，声音的频谱偏好 在AHL后约6个月内，从双耳发出的信号在对侧半球重新排列， 在同侧半球错位无论是动力学还是功能性后果， 大脑半球在SIN处理或关键听觉功能（如中枢增益适应）上的差异， 知道的此外，我们最近发现，正常听觉皮层中的神经元在听觉系统中是相当多样化的。 他们对背景噪音的容忍度有些神经元在有 噪声这种多样性创造了一个机会，以确定因素，决定噪音耐受性的皮层 神经元和AHL的后果。 我们建议对双侧皮质重组进行多方面的纵向分析， 啊。抑制性中间神经元的作用是特别感兴趣的，因为抑制性失调已经被证实。 这是听力损失的原因和后果。我们的目标将决定（1）AHL如何影响 （2）AHL如何影响皮层神经元的能力， 适应刺激水平和对比度的变化，以及（3）AHL的功能变化如何与结构变化相关。 以及皮层网络中抑制的功能表达。我们将估计光谱和时间调谐 属性，兴奋-抑制平衡和时间背景能力，这些都是最佳的关键 言语知觉我们将提供AHL中受损皮质SIN处理的第一次检查， 研究单声道和双耳信号解码能力在竞争的背景噪声水平的范围。 我们将从神经解剖学的角度， 确定了两个半球核心皮层区域中间神经元密度的变化。财富 这种方法产生的新的见解将解决许多悬而未决的问题， AHL及其动态时间过程的重组，为临床研究人员提供了新的和更好定义的 AHL的中心生物标志物，促进改善康复策略的发展，并提供新的 了解大脑如何从正常和受损听力的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.