Olivocochlear Reflex in Humans

描述（由申请人提供）：尽管对激活内侧耳蜗（MOC）对外毛细胞（ohc）的传出神经的许多外周影响以及这些影响的分子机制的了解有所进展，但MOC传出神经在人类听力中的功能意义仍然存在争议。MOC反射的基本特性，如频率特异性，目前尚不清楚。人类在注意力和信号的检测和/或辨别方面的传出功能的研究给出了看似矛盾的结果，但没有研究系统地改变参数以努力解决这些问题。MOC光纤改变了OHCs的状态，从而影响了耳声发射（oae）的产生。我们的方法是使用oae作为正常人MOC激活水平的非侵入性检测，并比较各种听力环境下的激活水平。实质性的技术进步使我们能够仅使用单一的低水平探测音调，我们可以证明它很少或根本不会引起MOC活动，以测量由对侧和/或同侧声音反射性引起的MOC激活，或由更高的大脑中枢引起的MOC激活，并确定这些影响是由MOC传出神经产生的还是由中耳肌肉产生的。为了了解人类MOC系统的功能组织，我们将确定人类探针频率的函数：（Aim la）同侧、对侧和双侧MOC反射的相对强度，（Aim lb） MOC反射的频率特异性，以及（Aim lc） MOC反射强度在耳蜗敏感性变化方面的作用。为了确定传出是否影响耳蜗调谐，我们将（目标2）测量由传出活动产生的耳蜗调谐的变化。为了解决MOC系统的功能意义，我们将系统地测量MOC激活水平（Aim 3a）在心理物理任务中，我们预测MOC激活将有助于表现（在噪声中识别瞬态信号）和那些没有预期好处的任务，以及（Aim 3b）在选择注意听觉与视觉刺激或听觉刺激的一个组成部分时。我们的实验结果将首次全面评估人类MOC系统的功能组织，并为MOC系统在人类听觉中的功能意义提供重要的见解。

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.