coupling and elastic loading affect the active response by the inner ear hair cell bundles耦合和弹性加载影响内耳毛细胞的积极响应包.pdfVIP

Coupling and Elastic Loading Affect the Active Response by the Inner Ear Hair Cell Bundles 1 1 1,2 Clark Elliott Strimbu , Lea Fredrickson-Hemsing , Dolores Bozovic * 1 Department of Physics Astronomy, University of California Los Angeles, Los Angeles, California, United States of America, 2 California NanoSystems Institute, University of California Los Angeles, Los Angeles, California, United States of America Abstract Active hair bundle motility has been proposed to underlie the amplification mechanism in the auditory endorgans of non- mammals and in the vestibular systems of all vertebrates, and to constitute a crucial component of cochlear amplification in mammals. We used semi-intact in vitro preparations of the bullfrog sacculus to study the effects of elastic mechanical loading on both natively coupled and freely oscillating hair bundles. For the latter, we attached glass fibers of different stiffness to the stereocilia and observed the induced changes in the spontaneous bundle movement. When driven with sinusoidal deflections, hair bundles displayed phase-locked response indicative of an Arnold Tongue, with the frequency selectivity highest at low amplitudes and decreasing under stronger stimulation. A striking broadening of the mode-locked response was seen with increasing stiffness of the load, until approximate impedance matching, where the phase-locked response remained flat over the physiological range of frequencies. When the otolithic membrane was left intact atop the preparation, the natural loading of the bundles likewise decreased their frequency selectivity with respect to that observed in freely oscillating bundles. To probe for signatures of the active process under natural loading and coupling conditions,