OLIVOCOCHLEAR EFFERENT SYSTEMS

多年来，人们一直不知道橄榄耳的内侧是如何 仅终止于外毛细胞的神经元可以强烈地 抑制有髓听神经纤维的活动， 仅起源于内毛细胞。最近，有一种 关于外毛细胞作用的思考发生了根本性的变化 在耳蜗力学中，以及耳蜗学的演示中 传出能在耳蜗内产生机械性变化。 这些都导致了一种假设，即对 内侧橄榄耳蜗区传出活动的听神经纤维 通过毛细胞水平的机械耦合来调节。 然而，几乎没有数据表明 产生这种耦合的机制或 耦合。我们的目标是确定这些属性，并 了解耦合是如何实现的。另一个目标是 确定传出活动可能发生的条件 在功能上意义重大。通过这些因素的结合，我们 试图了解中枢神经系统是如何影响 耳蜗机能。 提出了两个方面的工作。第一个项目的目标是 测量耳蜗骨的宏观力学变化 通过内侧橄榄耳蜗传出的活动，使用 在过去两年中发展了方法论。要做到这点， 传出引起的耳道声压变化将是 量过了。具体的实验将确定基本的 这些机械变化的属性，沿着 发生变化的耳蜗的长度，以及 它们提供声音放大的度量的程度 在耳蜗里。第二个项目试图确定 橄榄耳蜗声诱发活动对耳蜗声刺激的影响 传出物。这将通过测量声音引起的变化来完成 在耳道声压和复合动作电位中 听觉神经的损伤。

For many years it was unknown how medial olivocochlear neurons, which terminate only on outer hair cells, can strongly suppress activity of myelinated auditory-nerve fibers, which originate only from inner hair cells. Recently there has been a fundamental change in thinking about the role of outer hair cells in cochlear mechanics, and the demonstration that cochlear efferents can produce mechanical changes within the cochlea. These have led to the hypothesis that the suppression of auditory-nerve fibers by medial olivocochlear efferent activity is mediated through mechanical coupling at the hair cell level. There are almost no data, however, which indicate the mechanisms which produce this coupling or the properties of the coupling. Our goals are to determine these properties and to understand how the coupling is achieved. Another goal is to determine the conditions under which efferent activity might be functionally significant. Through the combination of these, we seek to learn how the central nervous system is able to influence cochlear function. Work in two areas is proposed. The first project is aimed at measuring the macromechanical changes in the cochlea produced by activity in medial olivocochlear efferents, using a methodology developed during the past two years. To do this, efferent-induced changes in ear-canal sound pressure will be measured. Specific experiments will determine the basic properties of these mechanical changes, the extent along the length of the cochlea over which the changes occur, and the degree to which they provide a measure of sound amplification within the cochlea. The second project seeks to determine the effects on the cochlea of sound-evoked activity of olivocochlear efferents. This will be done by measuring sound-evoked changes in ear-canal sound pressure and in the compound action potential of the auditory nerve.