ELECTRICALLY EVOKED OTOACOUSTIC EMISSION

对于复杂环境声音的感知，正常哺乳动物的耳朵具有极宽的动态范围和很高的频率选择性。这些听觉能力是通过耳蜗的高灵敏度、非线性和敏锐的调谐来实现的。提出了一种耳蜗放大器，用来放大低声引起的基底膜振动，提高机械频率的选择性。一种被广泛接受的推测是，放大器是通过从外毛细胞获取能量来工作的。虽然体外分离的OHC电动率已经得到了广泛的研究，耳蜗放大器的理论也得到了普遍的接受，但OHC电动率在体内和敏感耳蜗处的作用还没有得到验证。这项拟议工作的长期目标是确定耳蜗放大器反馈系统是否利用OHC产生的能量。为了实现这一长期目标，有必要对电诱发耳声发射(EEOAE)进行表征。在这项初步研究中，将通过重点研究EEOAE的精细结构来研究EEOAE。我们的工作假设是，耳道测量的EEOAE是耳蜗电诱发机械反应的多个分量的矢量总和。EEOAE的精细结构是不同成分相互抵消和增强的结果，这种精细结构反映了敏感耳蜗力学性能的正常。为了保持耳蜗的敏感性，将使用耳蜗外电刺激动物模型来产生EEOAE。采用一种检测单频信号多分量的方法对EEOAE进行分析。本研究的具体目的是：1)EEOAE的精细结构是如何产生的；2)EEOAE的精细结构与耳蜗声敏感度之间有什么关系；3)EEOAE和声诱发立方失真产物耳声发射(DPOAE)的精细结构之间有什么对应关系。将观察到EEOAE的每个分量对耳蜗声敏感度变化和同时呈现的声刺激的响应。还将研究EEOAE和DPOAE之间多组分的相似性。实验结果将证明这种精细结构是EEOAE多组分相互作用的结果，多组分分析方法是量化耳声发射精细结构的可靠方法。

For the perception of complex environmental sounds, the normal mammalian ear has an extremely wide dynamic range and high frequency selectivity. These auditory capabilities are achieved by cochlear high sensitivity, nonlinearity and sharp tuning. A cochlear amplifier has been proposed to amplify the basilarmembrane vibration evoked by low level sound and enhance mechanical frequency selectivity. A widely accepted speculation is that the amplifier works by obtaining energy from the outer hair cells (OHCs). Although isolated OHC electromotility in vitro has been intensively studied and the cochlear amplifier theory is generally accepted, the role of the OHC electromotility in the cochlear amplifier has not been tested in vivo and in sensitive cochleae. The long-term objective of the proposed work is to determine whether a cochlear amplifier feedback system utilizes OHC-generated energy. In order to achieve the long-term goal, it is essential to characterize the electrically evoked otoacoustic emissions (EEOAE). The EEOAE will be investigated in this initial study by focusing on the fine structure of the EEOAE. Our working hypothesis is that the ear canal-measured EEOAE is a vector summation of the multicomponents of the electrically evoked mechanical response in the cochlea. The fine structure of the EEOAE results from the cancellation and enhancement of the different components, and the fine structure indicates normal mechanical properties of a sensitive cochlea. To preserve cochlear sensitivity, an extracochlear electrical stimulation animal model will be used to generate the EEOAE. A method for detecting multicomponents of a single frequency signal will be implemented to analyze the EEOAE. The specific aims of the proposed study are to investigate i) how the fine structure of the EEOAE is generated; ii) what the relationship is between the EEOAE fine structure and cochlear sensitivity; and iii) what the correspondence is between the EEOAE and acoustically evoked cubic distortion product otoacoustic emission (DPOAE) fine structures. The responses of each of the components of the EEOAE to cochlear sensitivity changes and a simultaneously presented acoustic stimulus will be observed. Similarity of the multiple components between the EEOAE and the DPOAE will also be studied. Results from the proposed experiments will provide evidence that the fine structure results from the interaction of the multicomponents of the EEOAE, and that the multicomponent analysis method is a reliable method for quantification of the fine structure of the otoacoustic emissions.