Middlebrooks John C, Waters Michael F
Departments of Otolaryngology, Neurobiology and Behavior, Cognitive Sciences, and Biomedical Engineering, University of California, Irvine, Irvine, CA, United States.
Department of Neurology, Barrow Neurological Institute, Phoenix, AZ, United States.
Front Neurosci. 2020 Sep 16;14:571095. doi: 10.3389/fnins.2020.571095. eCollection 2020.
We live in complex auditory environments, in which we are confronted with multiple competing sounds, including the cacophony of talkers in busy markets, classrooms, offices, etc. The purpose of this article is to synthesize observations from a series of experiments that focused on how spatial hearing might aid in disentangling interleaved sequences of sounds. The experiments were unified by a non-verbal task, "rhythmic masking release", which was applied to psychophysical studies in humans and cats and to cortical physiology in anesthetized cats. Human and feline listeners could segregate competing sequences of sounds from sources that were separated by as little as ∼10°. Similarly, single neurons in the cat primary auditory cortex tended to synchronize selectively to sound sequences from one of two competing sources, again with spatial resolution of ∼10°. The spatial resolution of spatial stream segregation varied widely depending on the binaural and monaural acoustical cues that were available in various experimental conditions. This is in contrast to a measure of basic sound-source localization, the minimum audible angle, which showed largely constant acuity across those conditions. The differential utilization of acoustical cues suggests that the central spatial mechanisms for stream segregation differ from those for sound localization. The highest-acuity spatial stream segregation was derived from interaural time and level differences. Brainstem processing of those cues is thought to rely heavily on normal function of a voltage-gated potassium channel, Kv3.3. A family was studied having a dominant negative mutation in the gene for that channel. Affected family members exhibited severe loss of sensitivity for interaural time and level differences, which almost certainly would degrade their ability to segregate competing sounds in real-world auditory scenes.
我们生活在复杂的听觉环境中，在这种环境中我们会面临多种相互竞争的声音，包括繁忙市场、教室、办公室等场所中嘈杂的说话声。本文的目的是综合一系列实验的观察结果，这些实验聚焦于空间听觉如何有助于解开交织的声音序列。这些实验通过一个非语言任务“节奏掩蔽释放”统一起来，该任务应用于人类和猫的心理物理学研究以及麻醉猫的皮层生理学研究。人类和猫的听众能够从相隔仅约10°的声源中分离出相互竞争的声音序列。同样，猫初级听觉皮层中的单个神经元倾向于选择性地与两个相互竞争声源之一的声音序列同步，空间分辨率同样约为10°。空间流分离的空间分辨率在很大程度上取决于各种实验条件下可用的双耳和单耳声学线索。这与基本声源定位的一种测量方法——最小可听角度形成对比，最小可听角度在这些条件下显示出基本恒定的敏锐度。声学线索的差异利用表明，用于流分离的中枢空间机制与用于声音定位的机制不同。最高敏锐度的空间流分离源自双耳时间和强度差异。脑干对这些线索的处理被认为严重依赖于电压门控钾通道Kv3.3的正常功能。对一个在该通道基因中具有显性负突变的家族进行了研究。受影响的家族成员表现出对双耳时间和强度差异的严重敏感性丧失，这几乎肯定会降低他们在现实世界听觉场景中分离相互竞争声音的能力。
