Cortical Representation of Auditory Space

描述（由申请人提供）：正常的空间听力是听觉场景分析的关键，它帮助听者在存在竞争声音的情况下听出信号。这种能力的丧失可以说是轻度至中度听力损失患者最大的残疾之一。我们描述了人类心理物理学中场景分析的客观测量，并研究了麻醉猫的听觉皮层中一些自下而上的机制。现在，我们建议研究听觉场景空间分析的自上而下的皮层机制，利用密切协调的人类和猫的心理物理学，同时对猫的行为进行皮层记录。具体目标1解决空间流隔离，由听众解开多个交错的声音序列。在麻醉状态下，皮层神经元通过优先同步来自不同声源位置的两个竞争声音序列中的一个或另一个，表现出空间流分离的第一步。那些被麻醉的神经元，当然不知道哪个序列对应于目标或掩蔽。现在，我们将验证这样一个假设，即在皮质录音的任务执行过程中，猫听者通过促进与目标同步的模块和/或抑制与掩蔽器同步的模块来选择与目标声音序列同步的皮质模块。人类和猫的心理物理学和猫的皮层生理学将在听者注意空间或非空间隔离提示的情况下评估空间敏能性。临床报告和我们最近的结果表明，声音定位和空间流分离是由不同的皮质区域完成的。我们将在人类身上进行测试，扩展我们的观察，即空间隔离和定位在依赖刺激条件方面存在显著差异。在猫中，我们将对比几个候选皮质区域之间的空间流分离。目标2解决了信息掩蔽的空间释放，这是通过从并发掩蔽器中分离信号来改善声音接收。特别是，信息掩蔽是在信号和掩蔽器之间没有频谱重叠时发生的掩蔽。在人类和猫的心理物理学中，我们将测量给各种掩蔽成分的每次试验权重，并评估各种成分和空间线索对空间释放的贡献程度。在行为猫的皮层记录中，我们将量化带外频率成分对神经信号检测的掩盖，以及信号和掩蔽物的空间分离对这些成分的拒绝的影响。本研究探讨了单耳和双耳空间线索在现实生活听觉场景分析中的应用。它将产生的结果将为设计助听器和人工耳蜗的声音处理策略提供信息。新的动物模型将产生对皮层空间表征自上而下的任务依赖调节的新理解，增强空间听力缺陷的诊断和治疗。

DESCRIPTION (provided by applicant): Normal spatial hearing is key to auditory scene analysis, which aids listeners in hearing out signals in the presence of competing sounds. Loss of this ability arguably is one of the greatest disabilities of people with mild-to-moderate hearin loss. We have characterized objective measures of scene analysis in human psychophysics and have examined some bottom-up mechanisms in auditory cortex in anesthetized cats. Now, we propose to examine the top-down cortical mechanisms of spatial aspects of auditory scene analysis, utilizing closely coordinated human and cat psychophysics with simultaneous cortical recordings in behaving cats. Specific Aim 1 addresses spatial stream segregation, by which listeners disentangle multiple interleaved sound sequences. In anesthetized conditions, cortical neurons exhibit the first steps of spatial stream segregation by synchronizing preferentially to one or the other of two competing sound sequences from differing source locations. Those anesthetized neurons, of course don't know which sequences correspond to target or to masker. Now, we will test the hypothesis that, during task performance with cortical recording, feline listeners select cortical modules synchronized to target sound sequences, either by facilitating modules synchronized to the target and/or by suppressing modules synchronized to the masker. Human and cat psychophysics and cat cortical physiology will evaluate spatial acuity in conditions in which listeners attend to spatial or to non-spatial segregation cues. Clinical reports and our recent results suggest that sound localization and spatial stream segregation are accomplished by different cortical areas. We will test this in humans by extending our observations that spatial segregation and localization differ markedly in their dependence on stimulus conditions. In cats, we will contrast spatial stream segregation among several candidate cortical areas. Aim 2 addresses spatial release from informational masking, which is the improvement in sound reception by spatial separation of a signal from a concurrent masker. Informational masking, in particular, is the masking that occurs in the absence of spectral overlap between signal and masker. In human and cat psychophysics, we will measure the trial-by-trial weights given to various masker components and will evaluate the degree to which various components and spatial cues contribute to spatial release. In cortical recordings from behaving cats, we will quantify masking of neural signal detection by out-of-band frequency components and the effects of spatial separation of signal and masker on rejection of such components. This work explores the monaural and binaural spatial cues for real-life auditory scene analysis. It will yield results that will inform design of sound processing strategies for hearing aids and cochlear implants. The new animal models that are introduced will yield new understanding of top-down task-dependent modulation of cortical spatial representation, enhancing diagnosis and treatment of spatial hearing deficits.