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.

声音到达两只耳朵的时间略有不同，从而产生了指示声源位置的耳间时间差(ITD)提示。我们建议使用细胞外和细胞内技术记录蒙古沙土鼠内侧上橄榄(MSO)的ITD敏感神经元。MSO主细胞作为双耳兴奋性输入的符合探测器，其放电频率对ITD表现出敏感性。这项拟议的研究集中在两种机制上，这两种机制可以调整不同的MSO神经元适应不同的ITD。首先，立体声利用耳蜗行波延时对特征频率(CF)的依赖关系，通过系统地使双耳输入的CF值与MSO不匹配来创建ITD调谐。我们将通过定量评估神经最佳ITD与耳朵之间的CF差异的相关程度来检验立体声模型。其次，抑制性输入可能通过部分取消兴奋性输入、通过使神经膜更快地整合兴奋性事件和/或通过防止符合检测机制在高声电平时饱和来影响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剂进行了测量，但从未在体内进行过。我们将制作细胞内记录，以表征声诱发抑制对沙土鼠MSO神经元的影响。ITD编码不仅用作声源位置的提示，而且还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”，即一个发言者的演讲在许多其他发言者在场的情况下也很容易被理解。对于听力受损的听众来说，在这样的环境中理解语音尤其困难。对听觉系统如何编码ITD的更全面的了解可能有助于改进助听器或人工耳蜗的信号处理策略，从而改善听力受损的听者在具有挑战性的声学环境中的体验。