Experimental study of the cochlear amplifier

描述（由申请人提供）作为液压机械频率分析仪， 复杂的环境声音，哺乳动物的耳蜗能够处理 振幅，相位，和频率变化的声音在一个广泛的动态范围， 高频率和时间分辨率。这些能力是由于 耳蜗的灵敏度、非线性和尖锐的调谐。到 为了了解耳蜗如何工作，已经提出了耳蜗放大器（CA 一些研究者认为，这会放大基底膜（BM）的振动 唤起！通过低水平的声音和增强机械频率的选择性。的 CA被提议通过从外毛细胞（OHC）获得能量来工作， 以周期为基础，导致BM增强或抑制 振动通过正反馈或负反馈，这取决于频率。 本研究的目的是通过实验测试CA是否存在， 使用我们新开发的信号处理方法，并研究反馈 通过观察BM振动的相位关系， 由声音和电刺激引起的。以下具体目标将 被调查： i）EEOAE的长延迟分量（LDC）是否来自 特征频率在BM上的位置，ii）LDC的量是否 声能随耳蜗敏感性而变化，以及iii）CA是否 增益在数值上大于1，以及它是否取决于电平 电流或EEOAE声压。（4）振幅 由声和电刺激引起的BM速度的相位将 被测量为频率和强度的函数。的相位关系 OHC下面的将用于测试频率和电平依赖 CA的反馈机制。由于非侵入性方法， EEOAE的频率响应特性和固有的自测试特性 在该方法中，在本研究中CA的增益测量是 期望准确可靠。该项目提供了基本的 这些实验数据既能促进我们对耳蜗机制的理解 并将多组分分析方法作为一种重要工具， 听觉研究和临床诊断。

DESCRIPTION (provided by applicant) As a hydromechanical frequency analyzer of complex environmental sounds, the mammalian cochlea is capable of processing amplitude, phase, and frequency-varying sounds in a wide dynamic range and with a high degree of frequency and time resolution. These capabilities are due to the remarkable sensitivity, nonlinearity, and sharp tuning of the cochlea. To understand how the cochlea works, a cochlear amplifier (CA) has been proposed by some investigators, which amplifies the basilar membrane (BM) vibration evoked ! by low level sound and enhances mechanical frequency selectivity. The CA is proposed to work by obtaining energy from the outer hair cells (OHCs) on a cycle-by-cycle basis, resulting in enhancement or suppression of the BM vibration through either positive or negative feedback, depending on frequency. The aim of this study is to experimentally test if the CA exists through the use of our newly developed signal processing method and to study the feedback hypothesis of the CA by observing the phase relationships of the BM vibrations evoked by acoustical and electrical stimuli. The following specific aims will be investigated: i) whether the long delay component (LDC) of the EEOAE comes from the characteristic frequency place on the BM, ii) whether the amount of LDC acoustical energy changes with cochlear sensitivity, and iii) whether the CA gain is numerically greater than one and whether it is dependent on the level of electrical current or the EEOAE sound pressure. Finally, iv) the amplitude and phase of the BM velocity evoked by acoustical and electrical stimuli will be measured as functions of frequency and intensity. The phase relationship beneath the OHCs will be used to test the frequency and level dependent feedback mechanism of the CA. Because of the noninvasive approach, the wide frequency response feature of the EEOAE, and the inherent self-testing property of the method, the gain measurement of the CA in this proposed study is expected to be accurate and reliable. The project provides fundamental experimental data both for advancing our understanding of cochlear mechanisms and for using multiple component analysis method as an important tool for auditory research and clinical diagnosis.