Temporal weighting of interaural time and level differences

描述（由申请人提供）：本提案是对no - od -09-058号通知的回应：NIH宣布为竞争性修订申请提供恢复法案资金。拟议的研究将检查人类听觉皮层（AC）如何随时间对不同类型的双耳信息（特别是来自耳间时间差异（ITD）和耳间水平差异（ILD）的信息）的组合做出反应。ITD和ILD提供了一组主要的线索，使听者能够在空间中定位声音并分离竞争的声源。在理想情况下，这两种线索彼此一致，提供了关于听觉空间的冗余信息。然而，回声和混响会随着时间的推移扭曲过渡段和ILD值，降低定位和语音理解。这些影响在衰老、听力受损和使用人工耳蜗时尤为严重，可能反映了正常代偿机制的功能障碍，这些机制强调声音的某些方面（如开始时的过渡段）对回声的影响更强。该领域之前的研究已经调查了空间敏感性如何随着声音的时间过程而变化，一些研究表明，交流皮层维持着听觉空间线索的多种表征，并以一种对混响环境特征敏感的方式将这些线索上的信息结合起来。提出的修订使用功能性磁共振成像（fMRI）来测量交流反应对双耳刺激结构变化的敏感性。具体目的是研究交流皮层的活动是否对双耳信息的时间结构表现出敏感性（例如，交流皮层是否对声音开始时所包含的线索作出反应，而不是对声音的后半部分作出反应？）以及交流皮层的活动是否反映了刺激的感知或物理结构（当两者不同时）。目的进一步探讨各种候选空间线索（发病时和发病后的ITD和ILD）是否共同或独立地影响AC反应，以及这些贡献是否在人类AC的不同功能子区域中有所不同。

DESCRIPTION (provided by applicant): This proposal is in response to Notice Number NOT-OD-09-058: NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications. The proposed research will examine how the human auditory cortex (AC) responds to combinations of different types of binaural information (specifically, information from interaural time differences, or ITD, and interaural level differences, or ILD) over time. ITD and ILD provide the major set of cues that allow listeners to localize sounds in space and to segregate competing sound sources. In ideal situations, the two cues agree with one another, providing redundant information about auditory space. Echoes and reverberation, however, distort ITD and ILD values over time, degrading localization and speech understanding. These effects are especially severe in aging, hearing impairment, and cochlear-implant use, possibly reflecting dysfunction in normal compensatory mechanisms that emphasize aspects of sound (such as ITD at onset) that are more robust to effects of echoes. Previous research in this area has investigated how spatial sensitivity varies over the time-course of a sound, and some studies have suggested that the AC maintains multiple representations of auditory spatial cues, combining information across these cues in a manner that is sensitive to characteristics of the reverberant environment. The proposed revision uses functional magnetic resonance imaging (fMRI) to measure the sensitivity of AC responses to changes in the binaural configuration of a stimulus. The specific aims of address whether activity in the AC exhibits sensitivity to the temporal structure of binaural information (for example, does the AC respond to cues contained in the onset of a sound more than later parts of a sound?) and in turn whether AC activity reflects the perception or the physical configuration of a stimulus (when the two differ). The aims further address whether various candidate spatial cues (ITD and ILD at onset and thereafter) contribute together or independently in shaping AC responses, and whether those contributions vary across functionally distinct sub-regions of human AC. PUBLIC HEALTH RELEVANCE: Because a number of patient populations (aging, hearing impaired, cochlear implant users) are impaired when listening in noisy and reverberant environments, an improved understanding of the mechanisms that allow normal-hearing individuals to deal with echoes and reverberation will improve (a) theoretical descriptions of auditory processing deficits, and (b) algorithms for signal processing in hearing aids and cochlear implants. Furthermore, mapping the sensitivity of auditory cortical regions to variation in binaural parameters will improve our current understanding of how the brain processes sound, and how auditory cortex is organized, in normal and disordered populations.