Pathophysiological Research of Cochlear efferent System

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1)Investigation of cochlear physiology under derangement of efferent control system was conducted using otoacoustic emissions(OAEs)as an objective measure of the cochlear function. As the first step, an acoustic measuring system for known 4 classes of OAEs was constructed. In this series of research, many spontaneous OAE signals from guinea pigs, that had been regarded as extremely rare phenomenon, were closely examined. Basic features of guinea pig SOAEs were described and published. Efferent system did not look to affect on the SOAE in this animal.2)As an application of the acoustic measuring system which was established in the starting ear of the project, the distortion-product(DP)OAE was measured in normal and hearing-impaired ears. The DP audiogram was proved to be an excellent indicator of cochlear functional integrity. It provides frequencyspecific information of the cochlear physiology. However, the DP audiometry was not powerful enough to specify particular origin of a cochlear pathology. Further investigation seemed to be necessary before we can extract such an information from the DP audiometry.