ACTIVE FILTERING IN THE COCHLEA

最近的实验证据表明，外毛细胞的 哺乳动物的耳蜗充当机电放大器， 听觉灵敏度提高一百倍拟议的长期目标 研究是为了证实这一假设，并澄清我们的理解 潜在的机制。这项建议的具体目的是为了获得 实验证据支持一个详细的假设描述 耳蜗放大器的功能。我们的假设是， 外毛细胞受体电流调节力产生过程 其位于毛细胞索马中。这个力的生成过程是 耦合到行波传播的两种模式。的速率 两种模式不同，除了在有限的耳蜗区域上， 平等在这个等速放大区， 对内毛细胞的机械刺激显著增加。 我们计划通过以下方式来描述外毛细胞产生的力： 刺激电压依赖性外毛细胞长度的变化，通过 将交流电注入耳蜗的中阶。的 所产生的机械响应将被测量为耳声 发射以及移动的基底膜与光纤 位移探头我们还将研究其他耳蜗 操作，如传出刺激和同时声学 刺激.我们将寻找第二种模式的直接证据， 通过我们的力探头测量刚度进行行波传播， 我们的位移探头的位移梯度。 所提出的实验的结果以及先前的实验， 我们自己和其他人将被解释的援助计算 模型将使用两种类型的模型：微机械和 宏观力学的计算模型将基于物理， 包括器官的机械性能的具体描述， 皮层和顶盖膜以及毛细胞的机械-电 转导和外毛细胞运动。

Recent experimental evidence suggests that the outer hair cells of the mammalian cochlea act as electromechanical amplifiers which increase hearing sensitivity one-hundred fold. The long term goal of the proposed research is to confirm this hypothesis and to clarify our understanding of the underlying mechanisms. The specific aim of this proposal is to obtain experimental evidence in support of a detailed hypothesis describing the function of the cochlear amplifier. Our specific hypothesis is that the outer hair cell receptor current regulates a force-generation process which is located in the hair cell soma. This force generation process is coupled to two modes of traveling-wave propagation. The velocities of the two modes differ except over a limited cochlear region where they are equal. In this region of equal velocity amplification takes place and the mechanical stimulus to the inner hair cells is significantly increased. We plan to characterize the forces produced by outer hair cells by stimulating voltage-dependent outer hair cell length changes through the injection of alternating-current into the scala media of the cochlea. The resulting mechanical response will be measured both as an otoacoustic emission as well as movement of the basilar membrane with a fiber-optic displacement probe. We will also study the effects of other cochlear manipulations such as efferent stimulation and simultaneous acoustic stimulation. We will search for direct evidence of a second mode of traveling wave propagation by measuring stiffness with our force probe and displacement gradients with our displacement probe. The results of the proposed experiments as well as previous experiments by ourselves and others will be interpreted with the aid of computational models. Two types of models will be used: micromechanical and macromechanical. The computational models will be physically based and include specific descriptions of the mechanical properties of the organ of Corti and tectorial membrane as well as hair cell mechano-electric transduction and outer hair cell motility.