Temporal weighting of auditory spatial cues

描述(由申请人提供)：这项研究将考察听者如何结合不同类型的双耳线索(耳间时间差[ITD]和耳间电平差[ILD])、时间和跨频率的听觉空间信息，以便更好地理解混响环境中潜在的空间听力的动态过程。ITD和ILD提供了一套主要的线索，允许听众在空间中定位声音并隔离竞争的声源。在理想情况下，这些线索在频率上和两种线索类型之间是一致的，因此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这些线索，降低本地化和语音理解能力。虽然正常的双耳系统通过强调声音的强健方面(如开始时的ITD)来进行补偿，但年龄较大、听力受损或使用人工耳蜗的听者在存在回声和混响时仍会遇到困难。确定这些听觉处理缺陷的具体性质是困难的，因为人们对听力正常的听者的补偿机制知之甚少。过去的研究已经研究了空间线索的影响如何随声音的时间进程而变化(从而强调声音的首声)，以及在其频谱上(通常强调低频携带的空间信息)，但一个关键问题仍然没有答案：双耳处理的时间进程是随着频率的变化而变化的，还是当存在多个频率时？相反，高频和低频的相对贡献是否会在刺激持续时间内发生变化？这项拟议的研究的具体目的是通过绘制听者对不同频率、带宽的声音的耳间差异的敏感度的时间进程以及不同频率的双耳线索的一致性来解决这个问题。听者会用时变的ITD和/或ILD来判断声音的空间位置，而多元回归将被用来衡量这些判断对ITD和/或ILD的依赖性。回归系数将被用来构建时间加权函数(TWF)，该函数说明ITD和ILD随时间和跨频率整合的神经机制的动力学。平行实验将使用听觉皮质和下丘的神经成像，以及听觉外周的计算机模型，以努力确定这些影响发生在什么听觉处理水平上。 公共卫生相关性：由于许多患者群体(老龄化、听力受损、人工耳蜗者)在嘈杂和混响的环境中聆听时会受到损害，对听力正常的个体处理回声和混响的机制的更好理解将改进(A)听觉处理缺陷的理论描述，以及(B)助听器和人工耳蜗术中信号处理的算法。具体地说，跨频率映射ITD和ILD的敏感度的时间进程可以指导数字信号处理资源的分布，以最有效地保存相关的空间信息，并不强调潜在的误导性信息。

DESCRIPTION (provided by applicant): This research will examine how listeners combine auditory spatial information across different types of binaural cues (interaural time differences [ITD] and interaural level differences [ILD]), over time, and across frequency in order to better understand the dynamic processes underlying spatial hearing in reverberant environments. 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 cues agree across frequency and between the two cue types, and therefore provide redundant information about auditory space. Echoes and reverberation, however, distort these cues over time, degrading localization and speech understanding. Whereas the normal binaural system compensates by emphasizing robust aspects of the sound (such as ITD at onset), listeners who are aging, hearing-impaired, or using cochlear implants continue to experience difficulty in the presence of echoes and reverberation. Identifying the specific nature of these auditory processing deficits is difficult because so little is known about the compensatory mechanisms at work in normal-hearing listeners. Past research has investigated how the influence of spatial cues varies over the time-course of a sound (thereby emphasizing sound onsets), and across its frequency spectrum (typically emphasizing spatial information carried by low frequencies) but a key question remains unanswered: does the time-course of binaural processing vary across frequency or when multiple frequencies are present? Conversely, do the relative contributions of high and low frequencies change over the duration of a stimulus? The specific aims of the proposed study address this question by mapping the time-course of listeners' sensitivity to interaural differences for sounds varying in frequency, bandwidth, and the agreement of binaural cues across frequency. Listeners will judge the spatial positions of sounds with time-varying ITD and/or ILD, and multiple regression will be used to measure the dependence of those judgments on ITD and/or ILD. Regression coefficients will be used to construct temporal weighting functions (TWFs) that illustrate the dynamics of neural mechanisms for integration of ITD and ILD over time and across frequency. Parallel experiments will use neuroimaging of the auditory cortex and inferior colliculus, along with computer models of the auditory periphery, in an effort to identify at what level of auditory processing these effects take place. 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. Specifically, mapping the time-course of sensitivity to ITD and ILD across frequency could guide the distribution of digital signal-processing resources to most effectively preserve relevant spatial information and de-emphasize potentially misleading information.