The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Anders Fridberger - One of the best experts on this subject based on the ideXlab platform.
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Predicted motion of the Reticular Lamina for different parameter values.
2018Co-Authors: Nikola Ciganović, Rebecca L. Warren, Batu Keçeli, Stefan Jacob, Anders Fridberger, Tobias ReichenbachAbstract:(A) A small value of the Deiter’s cell extensibility Δ leads to a large Reticular-Lamina displacement. At a critical extensibility ΔC ≈ 1.2 (dashed strip) the displacement vanishes. The critical extensibility ΔC varies slightly with the outer hair cell contraction ϵ. (B) The Deiter’s cell extensibility Δ strongly influences the relation between Reticular-Lamina displacement (dashed) and Hensen-cell motion (solid) for the model parameter Γ = 0.1 as identified from comparison with experiments. The Hensen-cell motion for the model parameter Δ = 1.15 (red) is in very good qualitative agreement with experimental results of in vitro Hensen cell motion under applied current [20, 34]. Both the motion of the Hensen cells and of the Reticular Lamina depends nonlinearly on the contraction ϵ of the outer hair cells, and this nonlinearity is particularly pronounced for a Deiter’s cell extensibility Δ close to the critical value ΔC. (C) The nonlinear dependence in the Reticular-Lamina motion DRL on the contraction of the outer hair cells ϵ implies that the absolute value of the derivative of DRL with respect to the contraction ϵ varies with ϵ. The relative change is particularly strong for a large extensibility Δ of the Deiter’s cells, which has important functional implications.
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Direction of motion of the Hensen cells.
2018Co-Authors: Nikola Ciganović, Rebecca L. Warren, Batu Keçeli, Stefan Jacob, Anders Fridberger, Tobias ReichenbachAbstract:(A) Confocal microscopy shows the motion of the Reticular Lamina when a negative externally-applied current is switched to a positive current of equal magnitude, causing contraction of the outer hair cells. The green arrows show the displacement for the first and third row of outer hair cells (the displacement of the second row was similar to the first row). A pivot point emerges between the second and third row of outer hair cells: the first and second row move towards the basilar membrane whereas the third row moves away from it, following the displacement of the Hensen cells [20]. (B) Direction of displacement of the third row of outer hair cells. In this angle histogram, 0° corresponds to motion directed to the right in the image shown in panel A. According to morphometric measurements by Kelly, the basilar membrane is inclined by 37.26° on average with respect to the Reticular Lamina (dashed line) [42]. Our own measurements from anatomical 3D-reconstructions indicate that this inclination is slightly, but significantly, larger in the undamaged organ of Corti of our in vitro cochlear preparation (42.77° ± 6.43°, continuous black line; N = 13, p = 0.009 by two-tailed t-test, t = 3.09, d.f. = 12.). (C) The first row of outer hair cells (squares) moves only little. The larger displacement of third-row outer hair cells (circles) mirrors the large displacement of the Hensen cells. Error bars indicate the standard error of the mean from the different measurements. Data in (A-C) are from 683 measurements from 15 preparations for the first row of outer hair cells, and from 905 measurements from 18 preparations for the third row of outer hair cells. (D) The radial component of the Hensen-cell displacements was measured directly by tilting the preparation with respect to the interferometer beam. Representative data from one preparation show that the largest motion occurs in a direction with a small component towards the modiolus (red) for positive current injections, consistent with the Reticular-Lamina data shown in (A, B). Consistent results were obtained from four additional preparations.
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Resting length of outer hair cells can modulate Reticular-Lamina vibration.
2018Co-Authors: Nikola Ciganović, Rebecca L. Warren, Batu Keçeli, Stefan Jacob, Anders Fridberger, Tobias ReichenbachAbstract:How much Reticular-Lamina vibration is evoked by an oscillatory length change of the outer hair cells depends critically on the operating point set by the static length change of the outer hair cell. An oscillatory length change of an outer hair cell around an elongated state, characterized by a negative value of ϵ, leads to only a very small motion of the Reticular Lamina (blue). The vibration of the Reticular Lamina becomes increasingly larger for outer hair cells that oscillate around a progressively more contracted length (red and green).
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The cochlea structure and function.
2013Co-Authors: Dingjun Zha, Anders Fridberger, Fangyi Chen, Niloy Choudhury, Steven L Jacques, Ruikang K Wang, Sripriya Ramamoorthy, Alfred L. NuttallAbstract:a. The illustrated organ of Corti in cross-section. b. An OCT image of the organ of Corti in vivo. Circles mark the locations of vibration measurement. c. A cartoon of hair cell excitation without OHC length change. d. A cartoon showing that when depolarized, OHCs contract to become shorter in length. This will draw together the Reticular Lamina and basilar membrane; IHC, inner hair cell; OHC, outer hair cell; PCs, pillar cells.
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in vivo measurement of amplifying motion within the organ of corti under sound stimulation using optical coherence tomography
Proceedings of SPIE, 2012Co-Authors: Niloy Choudhury, Anders Fridberger, Fangyi Chen, Dingjun Zha, Jiefu Zheng, Steven L Jacques, Ruikang K Wang, Alfred L. NuttallAbstract:Hearing in mammals, depend on an amplifying motion which hypothetically uses force from outer hair cells (OHC) motility to enhance sound induced vibration of the organ of Corti of cochlea. In this hypothesis the differential motion among key structures in this organ and the timing of the OHC force generation is essential for cochlear amplification to occur. Using a time domain optical coherence tomography system which allows us to make vibration measurements we were able to measure differential motion of two functionally important surfaces, namely, basilar membrane and Reticular Lamina. The Reticular Lamina vibrates at higher amplitude than the basilar membrane and has significant phase lead over basilar membrane vibration. The differential motion, that is, different amplitude and phase of vibration, become less as the energy of the sound stimulus is increased and the amplification processes in the organ of Corti are quenched.
Jacques Boutet De Monvel - One of the best experts on this subject based on the ideXlab platform.
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Sound-evoked radial strain in the hearing organ.
Biophysical journal, 2007Co-Authors: Igor Tomo, Jacques Boutet De Monvel, Anders FridbergerAbstract:The hearing organ contains sensory hair cells, which convert sound-evoked vibration into action potentials in the auditory nerve. This process is greatly enhanced by molecular motors that reside within the outer hair cells, but the performance also depends on passive mechanical properties, such as the stiffness, mass, and friction of the structures within the organ of Corti. We used resampled confocal imaging to study the mechanical properties of the low-frequency regions of the cochlea. The data allowed us to estimate an important mechanical parameter, the radial strain, which was found to be 0.1% near the inner hair cells and 0.3% near the third row of outer hair cells during moderate-level sound stimulation. The strain was caused by differences in the motion trajectories of inner and outer hair cells. Motion perpendicular to the Reticular Lamina was greater at the outer hair cells, but inner hair cells showed greater radial vibration. These differences led to deformation of the Reticular Lamina, which connects the apex of the outer and inner hair cells. These results are important for understanding how the molecular motors of the outer hair cells can so profoundly affect auditory sensitivity.
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Imaging hair cell transduction at the speed of sound : dynamic behavior of mammalian stereocilia
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Anders Fridberger, Mats Ulfendahl, Igor Tomo, Jacques Boutet De MonvelAbstract:The cochlea contains two types of sensory cells, the inner and outer hair cells. Sound-evoked deflection of outer hair cell stereocilia leads to fast force production that will enhance auditory sensitivity up to 1, 000-fold. In contrast, inner hair cells are thought to have a purely receptive function. Deflection of their stereocilia produces receptor potentials, transmitter release, and action potentials in the auditory nerve. Here, we describe a method for rapid confocal imaging. The method was used to image stereocilia during simultaneous sound stimulation in an in vitro preparation of the guinea pig cochlea. We show that inner hair cell stereocilia move because they interact with the fluid surrounding the hair bundles, but stereocilia deflection occurs at a different phase of the stimulus than is generally expected. In outer hair cells, stereocilia deflections were ≈1/3 of the Reticular Lamina displacement. Smaller deflections were found in inner hair cells. The ratio between stereocilia deflection and Reticular Lamina displacement is important for auditory function, because it determines the stimulus applied to transduction channels. The low ratio measured here suggests that amplification of hair-bundle movements may be necessary in vivo to preserve transduction fidelity at low stimulus levels. In the case of the inner hair cells, this finding would represent a departure from traditional views on their function.
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Sound-induced differential motion within the hearing organ
Nature Neuroscience, 2003Co-Authors: Anders Fridberger, Jacques Boutet De MonvelAbstract:Hearing depends on the transformation of sound-induced basilar membrane vibration into deflection of stereocilia^ 1 on the sensory hair cells, but the nature of these mechanical transformations is unclear. Using new techniques to visualize and measure sound-induced vibration deep inside the moving organ of Corti, we found that two functionally crucial structures, the basilar membrane and the Reticular Lamina, have different centers of rotation, leading to shearing motion and rapid deformation for the mechanoreceptive outer hair cells. Structural relations within the organ of Corti are much more dynamic than previously thought, which clarifies how outer hair cell molecular motors can have such a powerful effect.
John J Guinan - One of the best experts on this subject based on the ideXlab platform.
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the spatial origins of cochlear amplification assessed by stimulus frequency otoacoustic emissions
Biophysical Journal, 2020Co-Authors: Shawn S Goodman, John J Guinan, Choongheon Lee, Jeffery T LichtenhanAbstract:Cochlear amplification of basilar membrane traveling waves is thought to occur between a tone's characteristic frequency (CF) place and within one octave basal of the CF. Evidence for this view comes only from the cochlear base. Stimulus-frequency otoacoustic emissions (SFOAEs) provide a noninvasive alternative to direct measurements of cochlear motion that can be measured across a wide range of CF regions. Coherent reflection theory indicates that SFOAEs arise mostly from the peak region of the traveling wave, but several studies using far-basal suppressor tones claimed that SFOAE components originate many octaves basal of CF. We measured SFOAEs while perfusing guinea pig cochleas from apex to base with salicylate or KCl solutions that reduced outer-hair-cell function and SFOAE amplification. Solution effects on inner hair cells reduced auditory nerve compound action potentials (CAPs) and provided reference times for when solutions reached the SFOAE-frequency CF region. As solution flowed from apex to base, SFOAE reductions generally occurred later than CAP reductions and showed that the effects of cochlear amplification usually peaked ∼1/2 octave basal of the CF region. For tones ≥2 kHz, cochlear amplification typically extended ∼1.5 octaves basal of CF, and the data are consistent with coherent reflection theory. SFOAE amplification did not extend to the basal end of the cochlea, even though Reticular Lamina motion is amplified in this region, which indicates that Reticular Lamina motion is not directly coupled to basilar membrane traveling waves. Previous reports of SFOAE-frequency residuals produced by suppressor frequencies far above the SFOAE frequency are most likely due to additional sources created by the suppressor. For some tones <2 kHz, SFOAE amplification extended two octaves apical of CF, which highlights that different vibratory motions produce SFOAEs and CAPs, and that the amplification region depends on the cochlear mode of motion considered. The concept that there is a single "cochlear amplification region" needs to be revised.
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non tip auditory nerve responses that are suppressed by low frequency bias tones originate from Reticular Lamina motion
Hearing Research, 2018Co-Authors: Hui Nam, John J GuinanAbstract:Abstract Recent cochlear mechanical measurements show that active processes increase the motion response of the Reticular Lamina (RL) at frequencies more than an octave below the local characteristic frequency (CF) for CFs above 5 kHz. A possible correlate is that in high-CF (>5 kHz) auditory-nerve (AN) fibers, responses to frequencies 1-3 octaves below CF (“tail” frequencies) can be inhibited by medial olivocochlear (MOC) efferents. These results indicate that active processes enhance the sensitivity of tail-frequency RL and AN responses. Perhaps related is that some apical low-CF AN fibers have tuning-curve (TC) “side-lobe” response areas at frequencies above and below the TC-tip that are MOC inhibited. We hypothesized that the tail and side-lobe responses are enhanced by the same active mechanisms as CF cochlear amplification. If responses to CF, tail-frequency, and TC-side-lobe tones are all enhanced by prestin motility controlled by outer-hair-cell (OHC) transmembrane voltage, then they should depend on OHC stereocilia position in the same way. To test this, we cyclically changed the OHC-stereocilia mechano-electric-transduction (MET) operating point with low-frequency “bias” tones (BTs) and increased the BT level until the BT caused quasi-static OHC MET saturation that reduced or “suppressed” the gain of OHC active processes. While measuring cat AN-fiber responses, 50 Hz BT level series, 70–120 dB SPL, were run alone and with CF tones, or 2.5 kHz tail-frequency tones, or side-lobe tones. BT-tone-alone responses were used to exclude BT sound levels that produced AN responses that might obscure BT suppression. Data were analyzed to show the BT phase that suppressed the tone responses at the lowest sound level. We found that AN responses to CF, tail-frequency, and side-lobe tones were suppressed at the same BT phase in almost all cases. The data are consistent with the enhancement of responses to CF, tail-frequency, and side-lobe tones all being due to the same OHC-stereocilia MET-dependent active process. Thus, OHC active processes enhance AN responses at frequencies outside of the cochlear-amplified TC-tip region in both high- and low-frequency cochlear regions. The data are consistent with the AN response enhancements being due to enhanced RL motion that drives IHC-stereocilia deflection by traditional RL-TM shear and/or by changing the RL-TM gap. Since tail-frequency basilar membrane (BM) motion is not actively enhanced, the tail-frequency IHC drive is from a vibrational mode little present on the BM, not a “second filter” of BM motion.
Yehoash Raphael - One of the best experts on this subject based on the ideXlab platform.
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organization of cell junctions and cytoskeleton in the Reticular Lamina in normal and ototoxically damaged organ of corti
Hearing Research, 1997Co-Authors: Elena V Leonova, Yehoash RaphaelAbstract:Abstract The Reticular Lamina creates an ion barrier, withstands mechanical stress in the organ of Corti and is able to maintain its integrity during and after severe hair cell loss. Tight junctions maintain the ionic gradient whereas adherens junctions and the cytoskeleton are responsible for the integrity and mechanical resistance of tissues. In this study we used immunofluorescence and electron microscopy to examine the distribution of proteins of tight junctions (cingulin), adherens junctions (E-cadherin, α- and β-catenin) and the cytoskeleton (actin, cytokeratin and tubulin) in whole-mounts of the normal and ototoxically damaged organ of Corti. In normal ears the proteins of adherens junctions were found in all cell types of the Reticular Lamina. We now demonstrate that all cells forming the Reticular Lamina partially overlap each other organizing extensive cell contacts with a complex three-dimensional shape. During scar formation, the tight junctions as well as adherens junctions between hair and supporting cells appeared in two distinct focal planes, which could help to preserve the ionic barrier and tissue integrity during hair cell degeneration. During scar formation all cytoskeletal structures in the Reticular Lamina were reorganized in a specific spatio-temporal pattern. We present a three-dimensional model of cell contact organization in the Reticular Lamina of normal ears and during scar formation.
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Scar formation in the vestibular sensory epithelium after aminoglycoside toxicity.
Hearing Research, 1994Co-Authors: Lawrence Z. Meiteles, Yehoash RaphaelAbstract:Hair cell degeneration and the repair process due to differing types of trauma have been studied extensively in the organ of Corti. It has been determined that, during scar formation, after differing types of trauma to the auditory sensory system, the Reticular Lamina is maintained with adherens junctions and tight junctions. We investigated the repair process within the vestibular epithelium. Hair cell degeneration was induced by the unilateral application of streptomycin to the inner ears of guinea pigs. Whole mount preparations of all five vestibular organs were processed and examined by fluorescence, light and electron microscopy. Scar formation was seen as early as 4 days post-treatment with streptomycin and was noted to coincide with hair cell degeneration. Neighboring supporting cells swelled and filled the space beneath the degenerating hair cell. Between three and five supporting cells participate in the reparative process. The distribution of cytokeratin is also altered during scar formation. The area once occupied by the hair cell becomes filled with cytokeratin-rich processes of supporting cells. It appears that differing numbers of supporting cells are involved in the reparative process within the vestibular sensory epithelium as compared to the auditory system. The Reticular Lamina remains intact at all times. This may possibly prevent mixing of fluids between different compartments in the inner ear and dysfunction of the vestibular sensory organs.
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structure of the Reticular Lamina and repair after noise injury
Revue de laryngologie - otologie - rhinologie, 1993Co-Authors: Yehoash Raphael, Brian D Athey, Y Wang, J E HawkinsAbstract:Laser Scanning Confocal Microscopy (LSCM) and specific labeling techniques were employed to examine the distributing of F-actin and microtubules in the Reticular Lamina of the guinea pig and monkey organ of Corti. Actin specific label was found in the circumferential belt of adherens junction at the borders between cells in the Reticular Lamina, and in the cuticular plate of hair cells. The distribution of actin in the adherens junction belt was asymmetric. Actin label was not found in the fonticulus, where the microtubule organizing center resides. Actin free areas were also found between the junctional actin and the cuticular plate. Microtubule specific label was very intense in supporting cells. In normal hair cells, the spatial distribution of tubulin at the Reticular Lamina is mutually exclusive with that of actin. After noise exposure, a belt of actin was found in the central portion of degenerating outer hair cells, possibly representing a constricted circumferential junction. Expanded supporting cells replaced degenerating hair cells and maintained the confluence of the Reticular Lamina during the dynamic process of scar formation. A complex network of actin-rich cables appeared at sites of degenerating inner hair cells, suggesting that more than two supporting cells are involved in scar formation for inner hair cells. LSCM proved an attractive method for analysis of the organ of Corti since preparation of the tissue is relatively rapid, preparation artefacts are minimized, different markers in the same specimen may be co-localized and out-of focus fluorescence blurring is eliminated.
Tianying Ren - One of the best experts on this subject based on the ideXlab platform.
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Two-tone distortion in Reticular Lamina vibration of the living cochlea
Communications biology, 2020Co-Authors: Tianying RenAbstract:It has been demonstrated that isolated auditory sensory cells, outer hair cells, can generate distortion products at low frequencies. It remains unknown, however, whether or not motile outer hair cells are able to generate two-tone distortion at high frequencies in living cochleae under the mechanical loads caused by surounding tissues and fluids. By measuring sub-nanometer vibration directly from the apical ends of outer hair cells using a custom-built heterodyne low-coherence interferometer, here we show outer hair cell-generated two-tone distortion in Reticular Lamina motion in the living cochlea. Reticular-Lamina distortion is significantly greater and occurs at a broader frequency range than that of the basilar membrane. Contrary to expectations, our results indicate that motile outer hair cells are capable of generating two-tone distortion in vivo not only at the locations tuned to primary tones but also at a broad region basal to these locations.
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Timing of the Reticular Lamina and basilar membrane vibration in living gerbil cochleae.
eLife, 2018Co-Authors: David B. Kemp, Tianying RenAbstract:Auditory sensory outer hair cells are thought to amplify sound-induced basilar membrane vibration through a feedback mechanism to enhance hearing sensitivity. For optimal amplification, the outer hair cell-generated force must act on the basilar membrane at an appropriate time at every cycle. However, the temporal relationship between the outer hair cell-driven Reticular Lamina vibration and the basilar membrane vibration remains unclear. By measuring sub-nanometer vibrations directly from outer hair cells using a custom-built heterodyne low-coherence interferometer, we demonstrate in living gerbil cochleae that the Reticular Lamina vibration occurs after, not before, the basilar membrane vibration. Both tone- and click-induced responses indicate that the Reticular Lamina and basilar membrane vibrate in opposite directions at the cochlear base and they oscillate in phase near the best-frequency location. Our results suggest that outer hair cells enhance hearing sensitivity through a global hydromechanical mechanism, rather than through a local mechanical feedback as commonly supposed.
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Reticular Lamina and basilar membrane vibrations in the basal turn of gerbil and mouse cochleae
2018Co-Authors: Tianying RenAbstract:Low-coherence interferometry in living cochleae has provided valuable information for understanding cochlear micromechanics. A recent measurement of the Reticular Lamina and basilar membrane vibrations in mouse cochleae, however, is inconsistent with data collected from guinea pig cochleae. To determine whether a species difference accounts for the observed difference, a custom-built heterodyne low-coherence interferometer was used to measure Reticular Lamina and basilar membrane vibrations at the basal turn of sensitive gerbil and mouse cochleae. For the gerbil and mouse, both the Reticular Lamina and basilar membrane vibrations show sharp tuning and nonlinear compressive growth near the best frequency. The magnitude of the Reticular Lamina vibration is significantly greater than that of the basilar membrane vibration not only near the best frequency, but also at low frequencies. The phase of the Reticular Lamina vibration leads the basilar membrane phase by up to 180-degrees at low frequencies, and this phase lead decreases with frequency, approaching zero near the best frequency. The best frequency of the Reticular Lamina and basilar membrane vibrations at the cochlear basal turn in mice is significantly higher than that in gerbils. Besides this difference, cochlear micromechanical responses in the gerbil are similar to those in the mouse. Thus, the current results indicate that gerbil and mouse cochleae detect and process sounds likely through a similar micromechanical mechanism.Low-coherence interferometry in living cochleae has provided valuable information for understanding cochlear micromechanics. A recent measurement of the Reticular Lamina and basilar membrane vibrations in mouse cochleae, however, is inconsistent with data collected from guinea pig cochleae. To determine whether a species difference accounts for the observed difference, a custom-built heterodyne low-coherence interferometer was used to measure Reticular Lamina and basilar membrane vibrations at the basal turn of sensitive gerbil and mouse cochleae. For the gerbil and mouse, both the Reticular Lamina and basilar membrane vibrations show sharp tuning and nonlinear compressive growth near the best frequency. The magnitude of the Reticular Lamina vibration is significantly greater than that of the basilar membrane vibration not only near the best frequency, but also at low frequencies. The phase of the Reticular Lamina vibration leads the basilar membrane phase by up to 180-degrees at low frequencies, and this...
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Reticular Lamina and basilar membrane vibrations in living mouse cochleae
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Tianying Ren, David B. KempAbstract:It is commonly believed that the exceptional sensitivity of mammalian hearing depends on outer hair cells which generate forces for amplifying sound-induced basilar membrane vibrations, yet how cellular forces amplify vibrations is poorly understood. In this study, by measuring subnanometer vibrations directly from the Reticular Lamina at the apical ends of outer hair cells and from the basilar membrane using a custom-built heterodyne low-coherence interferometer, we demonstrate in living mouse cochleae that the sound-induced Reticular Lamina vibration is substantially larger than the basilar membrane vibration not only at the best frequency but surprisingly also at low frequencies. The phase relation of Reticular Lamina to basilar membrane vibration changes with frequency by up to 180 degrees from ∼135 degrees at low frequencies to ∼-45 degrees at the best frequency. The magnitude and phase differences between Reticular Lamina and basilar membrane vibrations are absent in postmortem cochleae. These results indicate that outer hair cells do not amplify the basilar membrane vibration directly through a local feedback as commonly expected; instead, they actively vibrate the Reticular Lamina over a broad frequency range. The outer hair cell-driven Reticular Lamina vibration collaboratively interacts with the basilar membrane traveling wave primarily through the cochlear fluid, which boosts peak responses at the best-frequency location and consequently enhances hearing sensitivity and frequency selectivity.
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Reverse transduction measured in the living cochlea by low-coherence heterodyne interferometry.
Nature communications, 2016Co-Authors: Tianying Ren, Peter G. Barr-gillespieAbstract:It is generally believed that the remarkable sensitivity and frequency selectivity of mammalian hearing depend on outer hair cell-generated force, which amplifies sound-induced vibrations inside the cochlea. This 'reverse transduction' force production has never been demonstrated experimentally, however, in the living ear. Here by directly measuring microstructure vibrations inside the cochlear partition using a custom-built interferometer, we demonstrate that electrical stimulation can evoke both fast broadband and slow sharply tuned responses of the Reticular Lamina, but only a slow tuned response of the basilar membrane. Our results indicate that outer hair cells can generate sufficient force to drive the Reticular Lamina over all audible frequencies in living cochleae. Contrary to expectations, the cellular force causes a travelling wave rather than an immediate local vibration of the basilar membrane; this travelling wave vibrates in phase with the Reticular Lamina at the best frequency, and results in maximal vibration at the apical ends of outer hair cells.