COCHLEAR HAIR CELL TRANSDUCTION

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A variety of experiments are designed to examine the operation of the two types of sensory receptor cells of the mammalian hearing organ: inner hair cells and outer hair cells. It is now known that inner hair cells communicate auditory information to the brain, whereas outer hair cells modify the mechanical environment in the cochlea thereby producing amplification. In this work electrical responses to sound are recorded intracellularly from hair cells and extracellularly for their immediate environment in the organ of Corti of anesthetized guinea pigs. A significant portion of the proposed work is aimed at an investigation of the connections between single outer hair cell receptor potentials (their electrical response to sound) and gross extracellular electrical responses. It is proposed that the latter may influence the amplification process at high frequencies. Further, contemporary descriptions are sought of cochlear electroanatomy (its electrical impedance pattern), particularly at high frequencies, and of the organ of Corti proper. Finally, we aim to continue studies designed to evaluate cochlear nonlinear processes (two-tone suppression, low-frequency biasing, combination tone and harmonic production) as reflected in receptor potentials and as influenced by longitudinal location along the cochlear spiral. Aside from its intrinsic interest in describing cochlear nonlinear processing, much of this work is also used diagnostically to evaluate inner versus outer hair cell function and the sources of extracellular responses. A subset of these studies is aimed at finally resolving the long-standing discrepancy in the production of intracellular tonic receptor potentials, generated by outer hair cells in the high versus low frequency regions of the cochlea.