Cochlear Mechanisms: Structure, Function, and Models

Great advances have been made in understanding hearing in recent years. In particular, the mechanical function of the cochlea has become the focus of intense interest. This started in one direction, with the discovery of otoacoustic emissions in 1978, which required active mechanical amplification processes, as first postulated by Gold in 1948. Direct evidence for the role of this mechanism in sharpening-up the otherwise poor, basilar membrane tuning properties, was provided in 1982; and in 1983, motility was shown in outer hair cells. In parallel, an immense amount of work has been done on the electrophysiology of hair cells, following the first intracellular recordings in 1977. Over a longer time scale, models of basilar membrane motion have been developed and refined, and recently much effort has been put into incorporating active mechanisms and non-linear processes. It seemed an opportune time to bring together the leading workers in these various areas, to take stock of the whole field and to stimulate further progress. This book represents the proceedings of a NATO ARW on the Mechanics of Hearing held at the University of Keele, 3-8 July, 1988. The conception of the meeting owes much to earlier meetings held in Boston in 1985 (Peripheral Auditory Mechallisms, Eds. J.B. Allen, J.L.

Contenu

1. Hair Cell Ultrastructure.- Structural organization of the mammalian auditory hair cells in relation to micromechanics.- Observations on the cytoskeleton and related structures of mammalian cochlear hair cells.- A comparative study of actin filaments in cochlear hair cells: outer hair cells in the apex of the guinea pig cochlea contain a unique ultrastructural feature.- The lateral walls of inner and outer hair cells.- Tip-link organization in relation to the structure and orientation of stereovillar bundles.- 2. Micromechanical measurements and models.- Hair cell mechanics controls the dynamic behaviour of the lateral line cupula.- Aminoglycoside antibiotics and lectins cause irreversible increases in the stiffness of cochlear hair-cell stereocilia.- Mechanical analysis of hair cell microstructure and motility.- A model for bidirectional transduction in outer hair cells.- A three-degree-of-freedom active micromechanical model of the cochlear partition.- Outer hair cells possess acetylcholine receptors and produce motile responses in the organ of Corti.- Mechano-electrical transduction in turtle hair cells.- Transducer motor coupling in cochlear outer hair cells.- Structure of the cortical cytoskeleton in outer hair cells from the guinea pig organ of corti.- Gating compliance, a reduction in hair-bundle stiffness associated with the gating of transduction channels in hair cells from the bullfrog's sacculus.- Simultaneous recording of fluctuations of hair-bundle defection and intracellular voltage in saccular hair cells.- Micromechanical movements of chick sensory hair bundles to sinusoidal stimuli.- Micromechanical basis of high-frequency tuning in the bobtail lizard.- Mechanical coupling between inner and outer hair cells in the mammalian cochlea.- 3.Electrophysiological Measurements.- Phase reversal of ohc response at high sound intensities.- Outer hair cell receptor current and its effect on cochlear mechanics.- Saturation of receptor currents accounts for two-tone suppression.- Components of the membrane current in guinea pig inner hair cells.- Cochlear nonlinearities reflected in inner hair cell responses.- Asymmetries in motile responses of outer hair cells in simulated in vivo conditions.- Round window cochlear microphonic and atrophy of short and middle stereocilia on outer hair cells in hydropic cochleas in guinea pigs.- Postnatal developement of the cochlea in horseshoe bats.- On the origin of interspecific differences in auditory susceptibility.- Response properties of turtle auditory afferent nerve fibers: evidence for a high order tuning mechanism.- Cochlear filtering: a view seen through the temporal discharge patterns of single cochlear nerve fibres.- Cochlear nonlinearities implied by the differences between transient onsets and offsets to a tone burst.- Peak-splitting: intensity effects in cochlear afferent responses to low frequency tones.- 4. Discussion Session I.- 5. Otoacoustic Emissions.- Historical background to the proposal, 40 years ago, of an active model for cochlear frequency analysis.- CM and OAE changes following transient efferent excitation.- Effect of visual selective attention on otoacoustic emissions.- Tracking and interpretive models of the active-nonlinear cochlear response during reversible changes induced by aspirin consumption.- Analysis and influence of lidocaine on evoked otoacoustic emissions from tinnitus sufferers.- An electrical correlate of spontaneous otoacoustic emissions in a frog, a preliminary report.- Otoacoustic evidence for nonlinear behaviour in frogs'hearing: suppression but no distortion products.- Otoacoustic emissions and cochlear travelling waves.- 6. Macromechanical Measurements.- Nonlinear interactions in the mechanical response of the cochlea to two-tone stimuli.- Determinants of high-frequency sensitivity in the bird.- Mechanical response of the outer hair cell region of an isolated guinea pig cochlea in vitro.- 7. Nonlinear Models.- Power-law nonlinearities: a review of some less familiar properties.- Distortion product responses of saturating nonlinearities.- 8. Cochlear Models.- Realistic basilar membrane tuning does not require active processes.- A model of peripheral auditory preprocessing.- On the stability of cochlear mechanical models.- Time-domain solutions for 1D, 2D & 3D cochlear models.- Is basilar membrane tuning the same as neural tuningwhere do we stand?.- On the nature of cochlear resonance.- 9. Discussion Session II.- Photograph of Participants.- Names and Addresses of Participants.- Names of Local Organising Committee and Session Chairmen.- Author Index.