ACTIVE FILTERING IN THE COCHLEA

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DESCRIPTION (provided by applicant): Recent experimental evidence suggests that the outer hair cells (OHC) of the mammalian cochlea act as part of an electromechanical amplifier that increases 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 goals of this proposal are: to determine which properties of the organ of Corti are responsible for the cochlear frequency map, to establish how the OHCs amplify the traveling wave, to determine how the motion of the cochlear partition is coupled to IHC stereocilia motion, to establish how otoacoustic emissions relate to cochlear partition motion, and to develop a better understanding of the mechanisms of acoustic trauma. To achieve these goals we plan to develop quantitative anatomical models of the cochlea, to measure the mechanical impedance of the cellular and extracellular elements of the organ of Corti, to image the motion of the elements of the organ of Corti in response to electrical and mechanical stimulation in excised cochleas, and to conduct physiological experiments in live animals. The results of the proposed experiments together with 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 as physically based as possible and will include specific descriptions of the mechanical properties of the organ of Corti, basilar membrane and tectorial membrane, hair cell mechanoelectric transduction and QHC motility, and inner hair cell physiology.