Olivocochlear Reflex in Humans

描述(由申请人提供)：尽管在了解激活内侧橄榄耳蜗区(MOC)传出到外毛细胞(OHC)的许多外周效应以及这些效应背后的分子机制方面取得了进展，但MOC传出在人类听力中的功能意义仍然存在争议。对MOC反射的基本性质，如频率特异性，人们知之甚少。对人类注意的传出功能以及对信号的检测和/或辨别的研究，给出了似乎相互矛盾的结果，但没有研究系统地改变参数来努力解决这些问题。MOC纤维改变了OHC的状态，从而影响耳声发射(OAE)的产生。我们的方法是使用耳声发射作为正常人类受试者MOC激活水平的非侵入性分析，并比较各种听环境中的激活水平。实质性的技术进步允许我们只使用一个低水平的探测音，我们可以证明它只引起很少或根本没有MOC活动，来测量由对侧和/或同侧声音反射性地引起的MOC激活，或者由更高的大脑中枢引起的MOC激活，并确定这些影响是由MOC传出还是由中耳肌肉产生。为了了解人类MOC系统的功能组织，我们将在人类中确定探测频率的函数：(Aim 1a)同侧、对侧和双侧MOC反射的相对强度，(Aim 1b)MOC反射的频率特异性，以及(Aim Lc)根据耳蜗敏感度的变化而产生的MOC反射强度。为了确定传出活动是否影响耳蜗调优，我们将(目标2)测量传出活动所产生的耳蜗调优变化。为了解决MOC系统的功能意义，我们将系统地测量心理物理任务中MOC的激活水平(目标3a)，在这些任务中，我们预测MOC的激活将有助于表现(辨别噪声中的瞬时信号)和那些预期没有益处的任务，以及(目标3b)在选择性注意听觉与视觉刺激或听觉刺激的一个成分的过程中。我们的实验结果将首次对人类MOC系统的功能组织进行全面评估，并应对MOC系统在人类听力中的功能意义提供重要的洞察。

DESCRIPTION (provided by applicant): Despite advances in understanding many peripheral effects of activating medial olivocochlear (MOC) efferents to outer hair cells (OHCs), as well as the molecular mechanisms underlying those effects, the functional significance of MOC efferents in human audition remains controversial. Basic properties of the MOC reflexes, such as their frequency specificity, are poorly understood. Studies of human efferent function in attention, and detection and/or discrimination of signals, have given seemingly contradictory results, but no study has systematically varied parameters in an effort to resolve these issues. MOC fibers alter the state of the OHCs and thereby affect the generation of otoacoustic emissions (OAEs). Our approach is to use OAEs as a non-invasive assay of MOC activation levels in normal human subjects, and to compare activation levels in a variety of listening contexts. Substantial technical advances allow us to use only a single low-level probe tone, which we can demonstrate evokes little or no MOC activity, to measure MOC activation elicited reflexly by contralateral and/or ipsilateral sounds, or elicited by higher brain centers, and to determine whether these effects are produced by MOC efferents or middle-ear-muscles. To understand the functional organization of the human MOC system, we will determine in humans as functions of probe frequency: (Aim la) the relative strength of the ipsilateral, contralateral and bilateral MOC reflexes, (Aim lb) the frequency specificity of MOC reflexes, and (Aim lc) MOC reflex strength in terms of the changes in cochlear sensitivity produced. To determine if efferents affect cochlear tuning, we will (Aim 2) measure the changes in cochlear tuning produced by efferent activity. To address the functional significance of the MOC system, we will systematically measure MOC activation levels (Aim 3a) in psychophysical tasks in which we predict that MOC activation will aid performance (discrimination of transient signals in noise) and those in which no benefit is anticipated, and (Aim 3b) during selective attention to auditory vs. visual stimuli, or to one component of an auditory stimulus. The results of our experiments will provide the first comprehensive assessment of the functional organization of the human MOC system and should provide significant insight into the functional significance of the MOC system in human audition.