Neural Mechanisms of Interaural Time Difference Coding

耳间时差编码的神经机制

• 批准号: 6890528
• 负责人: KENNETH E HANCOCK
• 金额: $ 7.55万
• 依托单位: MASSACHUSETTS EYE AND EAR INFIRMARY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2008-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6890528
• 关键词: binaural hearing; cues; electrostimulus; gerbil /jird; histology; neural information processing; olivary body; sensory signal detection; sound perception; statistics /biometry

Sounds reach the two ears at slightly different times, creating an interaural time difference (ITD) cue to the location of the sound source. We propose to use extracellular and intracellular techniques to record from ITD sensitive neurons in the medial superior olive (MSO) of Mongolian gerbils. MSO principal cells function as coincidence detectors of binaural excitatory inputs, and as a result show ITD sensitivity in their firing rates. The proposed research focuses on two mechanisms that may tune different MSO neurons to different ITDs. First, stereausis exploits the dependence of the cochlear traveling wave delay on characteristic frequency (CF) to create ITD tuning by systematically mismatching the CFs of the binaural inputs to the MSO. We will test the stereausis model by quantitatively evaluating the extent to which neural best ITD is correlated with the CF difference between the ears. Second, inhibitory inputs may affect ITD coding in the MSO by partially canceling excitatory inputs, by causing the neural membrane to integrate excitatory events more rapidly, and/or by preventing the coincidence detection mechanism from saturating at high sound levels. Inhibitory synaptic potentials have been measured in a few studies using slice preparations, but never in vivo. We will make intracellular recordings to characterize the effects of acoustically-evoked inhibition on MSO neurons in the gerbil. The ITD code is useful not just as a cue to sound source location, but also for extracting signals from background noise. A familiar example is the "cocktail party effect," in which speech from one speaker can be understood easily despite the presence of many other speakers. Comprehending speech in such environments is particularly troublesome for hearing impaired listeners. A more complete understanding of how the auditory system encodes ITD may help improve hearing aids or signal processing strategies for cochlear implants and thus improve the experience of hearing impaired listeners in challenging acoustic environments.

声音到达双耳的时间略有不同，从而产生了一个耳间时间差（ITD）提示声源的位置。本研究拟采用细胞外和细胞内两种方法记录蒙古沙鼠内侧上级橄榄核（MSO）内ITD敏感神经元的活动。MSO主细胞作为双耳兴奋性输入的重合检测器，其结果显示ITD敏感性在其放电率。拟议的研究集中在两种机制，可能会调整不同的MSO神经元不同的ITD。首先，立体声利用耳蜗行波延迟对特征频率（CF）的依赖性，以通过将双耳输入的CF系统地失配到MSO来创建ITD调谐。我们将通过定量评估神经最佳ITD与耳朵之间的CF差异相关的程度来测试立体声模型。第二，抑制性输入可以通过部分地取消兴奋性输入、通过使神经膜更快速地整合兴奋性事件和/或通过防止重合检测机制在高声级下饱和来影响MSO中的ITD编码。抑制性突触电位已经在一些研究中使用切片制备进行了测量，但从未在体内进行。我们将进行细胞内记录来表征声诱发抑制对沙土鼠MSO神经元的影响。ITD码不仅可以作为声源定位的线索，还可以从背景噪声中提取信号。一个熟悉的例子是“鸡尾酒会效应”，其中一个发言者的讲话可以很容易地理解，尽管有许多其他发言者在场。在这样的环境中理解语音对于听力受损的听众来说特别麻烦。更全面地了解听觉系统如何编码ITD可能有助于改善助听器或人工耳蜗植入的信号处理策略，从而改善听力受损听众在具有挑战性的声学环境中的体验。