Olivocochlear Efferent Systems and Cochlear Physiology

描述（由申请人提供）：我们的目标是了解外毛细胞（ohc）如何产生哺乳动物听觉的高灵敏度。在了解离体耳蜗羟基碳化物的特性方面已经取得了很大的进展，但关于羟基碳化物如何在完整耳蜗中起作用仍有一些基本的未解问题。内侧耳蜗（MOC）传出神经元支配ohc，为理解ohc机制提供了重要工具。为了研究OHCs在体内的机械效应，我们将测量基底膜（BM）运动和听神经（AN）放电模式，以及电刺激MOC传出神经在这些反应中产生的变化。

DESCRIPTION (provided by applicant): Our goal is to understand how outer hair cells (OHCs) produce the high sensitivity of mammalian hearing. Great progress has been made in understanding the properties of isolated OHCs, but there are fundamental unanswered questions about how OHCs work in intact cochleas. Medial olivocochlear (MOC) efferent neurons innervate OHCs and provide an important tool for understanding OHC-based mechanisms. To study the mechanical effects of OHCs in vivo, we will measure basilar-membrane (BM) motion and auditory-nerve (AN) firing patterns and the changes produced in these responses by electrical stimulation of MOC efferents. Our recent work provides strong evidence for the existence of a second traveling wave along the cochlea, a wave that may couple OHC motility to BM motion. The proposed work will characterize the properties of this second wave and its relationship to the classic transverse traveling wave. This wil be done (1) at frequencies well below the local characteristic frequency (CF), where stiffness dominates the mechanical response and the effects of the two traveling waves can be studied without the complications produced by cochlear amplification, and (2) at frequencies near CF where the cochlear amplifier has its primary effects. Our work, and that of others, has shown that the "slow effect" of MOC stimulation is due to a decrease in OHC stiffness. This stiffness change will be exploited to determine how OHC stiffness affects cochlear properties such as CF, and to test the OHC piezoelectric theory, a theory that may account for how OHC somatic motility can be effective at frequencies above the OHC membrane cut-off frequency. The results of the proposed work will help to flesh out a new picture of cochlear mechanics. Mechanics is a key area of cochlear function that is disrupted by many of the pathologies that affect hearing. Understanding cochlear mechanics, and the role of OHCs in cochlear mechanics, is essential for progress in almost all aspects of hearing.