Neural coding of sound location under normal and impaired hearing conditions

正常和听力受损条件下声音位置的神经编码

• 批准号: 8689281
• 负责人: MITCHELL LEE DAY
• 金额: $ 16.4万
• 依托单位: MASSACHUSETTS EYE AND EAR INFIRMARY
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-02-07 至 2017-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8689281
• 关键词: Acoustic Trauma; Address; Animals; Auditory; Auditory Brainstem Responses; Auditory system; Bilateral; Bilateral Hearing Loss; Brain; Brain Stem; Cell Nucleus; Code; Comprehension; Cues; Data; Ear; Environment; Hearing; Human; Individual; Inferior Colliculus; Location; Measures; Modality; Neurons; Noise; Oryctolagus cuniculus; Pattern; Performance; Population; Process; Property; Psychophysics; Scientist; Sensorineural Hearing Loss; Sensory; Sound Localization; Source; Speech; Stimulus; Testing; Time; Training; auditory pathway; awake; base; early onset; hearing impairment; interest; neuromechanism; public health relevance; relating to nervous system; research study; response; sensory system; sound

DESCRIPTION (provided by applicant): The binaural cues used to localize sound in the horizontal plane (i.e., azimuth) and the neural mechanisms by which these cues are encoded in the responses of neurons in the central auditory system are well known. What remains unclear is how the combined responses across neurons that are sensitive to ITD and ILD form a neural representation of azimuthal location that is robust to changes in natural auditory scenes. This proposal focuses on how the population response of neurons in the inferior colliculus (IC) encodes sound source azimuth with respect to two of these changes: 1) with changes in sound level, and 2) in the presence of a competing sound source. The third aim investigates changes in the population encoding of azimuth brought about by sensorineural hearing loss (SNHL). These aims will be addressed by collecting azimuth tuning functions from single-unit recordings in the IC of awake rabbits. Population IC responses will be used to train and test a maximum-likelihood decoder of source azimuth as a means to both evaluate the azimuth encoding ability of population activity, and to test whether patterns of population activity specific to source azimuth are robust to changes in other sound parameters (e.g., sound level). Experiments in Aim 1 will use azimuth tuning functions collected at multiple sound levels to test whether performance of the decoder is invariant to sound level; or in other words, whether the location-specific patterns of activity across IC neurons (or a subpopulation of neurons) remain largely similar between sound levels. Experiments in Aim 2 will investigate the neural coding of sound location in a multisource environment with different sound source onsets. When the onset of one sound source precedes another, IC neurons may adapt to the early-onset source and "unmask" azimuth information for the later arriving source. To test this hypothesis, azimuth tuning functions will be collected under target-alone and target-plus-interferer conditions (both simultaneous and onset difference). The decoder will be used to assess invariance of IC activity patterns when trained on target-alone data and tested on target-plus- interferer data. Finally, experiments in Aim 3 will test whether or not the azimuth encoding of IC neurons is degraded in rabbits with bilateral SNHL-the leading form of permanent hearing loss. SNHL will be induced in rabbits via high-level noise exposure. Following verification of permanent hearing loss two weeks after exposure, azimuth tuning functions will be measured in the IC. Decoder performance will be compared between noise-exposed rabbits and unexposed rabbits to evaluate whether there is a decrease in the ability of IC neurons to encode source azimuth following SNHL. Azimuth tuning will also be measured under conditions where only interaural time difference or interaural level difference varies with azimuth to assess any specific deficit i the neural representation of either binaural cue.

描述（由申请人提供）：用于在水平面中定位声音的双耳提示（即方位角）和这些提示在中央听觉系统中神经元响应中编码的神经机制是众所周知的。尚不清楚的是，对ITD和ILD敏感的神经元的组合反应如何形成方位角位置的神经表示，这对自然听觉场景的变化具有牢固的变化。该提案的重点是下丘（IC）（IC）中神经元的种群反应相对于其中两个变化编码声源方位角：1）随着声音水平的变化，以及2）在存在竞争性的声源的情况下。第三个目标调查了传感器听力损失（SNHL）带来的方位角编码的人群的变化。这些目标将通过从清醒兔子中的单单元录音中收集方位角调谐功能来解决。人群IC响应将用于训练和测试源方位角的最大样品解码器，作为评估人口活动的方位角编码能力的一种手段，并测试特定于源源方位角的模式是否对其他声音参数的变化具有鲁棒性（例如，声音级别）。 AIM 1中的实验将使用在多个声音级别收集的方位角调谐功能来测试解码器的性能是否不变到声级；或换句话说，在声音级别之间，IC神经元（或神经元亚群）跨IC神经元（或亚群）的活动模式是否在很大程度上相似。 AIM 2中的实验将调查具有不同声源的多源环境中声音位置的神经编码。当一个声源的发作在另一个声源之前，IC神经元可能会适应早期发作的源，并为后期到达源“揭示”方位角信息。为了检验这一假设，将在目标 - 单位和距离裂缝条件（同时和发作差异）下收集方位角调谐功能。解码器将用于评估IC活性模式的不变性，当对目标数据培训并在目标加人干扰器数据上进行测试。最后，AIM 3中的实验将测试IC神经元的方位角编码是否在双侧SNHL（永久性听力损失的领先形式）中降解。 SNHL将通过高级噪声暴露在兔子中诱导。在暴露两周后验证永久性听力损失后，将在IC中测量方位调节功能。将在噪声暴露的兔子和未暴露的兔子之间比较解码器的性能，以评估IC神经元在SNHL后编码源方位角的能力是否有降低。在只有在室内的时间差或手段间差异的条件下，方位角调整也将随着方位角而变化，以评估任何特定的赤字I i双耳提示的神经表示。