Neural Mechanisms of Interaural Time Difference Coding

耳间时差编码的神经机制

• 批准号: 7019964
• 负责人: KENNETH E HANCOCK
• 金额: $ 7.37万
• 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/7019964
• 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.

声音在略有不同的时间到达了两个耳朵，从而在声源的位置创造了一个间的时间差（ITD）提示。我们建议使用细胞外和细胞内技术来记录蒙古语沙鼠内侧橄榄（MSO）中ITD敏感神经元的记录。 MSO主细胞充当双耳兴奋性输入的巧合探测器，因此显示出发射速率的敏感性。拟议的研究集中于两种可能将不同的MSO神经元调节到不同ITD的机制。首先，stereausis利用了耳蜗延迟对特征频率（CF）的依赖性，从而通过系统地使双耳输入的CF与MSO进行了系统不匹配来创建ITD调整。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骨usis模型。其次，通过使神经膜更快地整合兴奋性事件和/或防止巧合检测机制在高声音水平上饱和，可以通过部分取消兴奋性输入来影响MSO中ITD编码的ITD编码。在几项使用切片制剂的研究中，已经测量了抑制性突触电位，但从未体内。我们将制作细胞内记录，以表征听觉诱发的抑制对Gerbil中MSO神经元的影响。 ITD代码不仅可以作为声音源位置的提示，而且用于从背景噪声中提取信号。一个熟悉的例子是“鸡尾酒会效应”，尽管许多其他演讲者在场，但可以轻松理解一位演讲者的演讲。对于听力受损的听众，在这种环境中理解语音尤其麻烦。对听觉系统如何编码ITD的更全面了解可能有助于改善耳蜗植入物的助听器或信号处理策略，从而改善在挑战性的声学环境中听力受损的听众的经验。