scholarly journals An Analytical Mechanical Model of Corti in the Cochlea

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Jiangtao Su ◽  
Wenjuan Yao ◽  
Zhengshan Zhao
Keyword(s):  
Mechanical Model ◽  
Basilar Membrane ◽  
Low Frequency ◽  
Organ Of Corti ◽  
Negative Influence ◽  
Outer Hair Cells ◽  
Tectorial Membrane ◽  
Response Patterns ◽  
Motion Patterns ◽  
Loss Of Hearing

The organ of Corti (OC) in the cochlea is a significant structure for feeling sound. The components of OC and the interaction of the part with the surroundings contribute to the fact that the passive tuning of the cochlear macrostructure is unclear. Based on the interaction between the basilar membrane (BM), tectorial membrane (TM), reticular lamina (RL), and various parts of OC, a mechanical model of the cochlea is established to study the motion patterns of each part under the action of a certain pressure. The variational principle is applied to the calculation of the analytical expression of the displacement of the BM. The results of the analytical solution differ little from the experimental value, and the variation trend is consistent, which presents the correctness of the model. The parameter sensitivity analysis is carried out for obtaining the interaction principle and the primary and secondary roles of each component in the process of the sense of sound. The results show that the absence of the TM and the decrease in the stiffness of the outer hair cells (OHCs) and OHC bundles will shift vibratory response patterns to lower frequencies, in which the lack of TM will result in the greatest reduction of CF. The absence of RL exerts a negative influence on the CF as well as the amplitude of BM and thereby loss of hearing. Therefore, both TM and RL are essential structures during the process of the sense of sound. At the same time, the resonance frequency at the base of the BM is concentrated on the high-frequency segment, while the apex of the BM is mainly in the low frequency. Different points of BM correspond to different CF, which demonstrates the frequency selectivity of the BM.

scholarly journals Finite-element model of the active organ of Corti

2016 ◽  
Vol 13 (115) ◽  
pp. 20150913 ◽  
Author(s):  
Guangjian Ni ◽  
Stephen J. Elliott ◽  
Johannes Baumgart
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Basilar Membrane ◽  
Imaging Techniques ◽  
Fluid Pressure ◽  
Organ Of Corti ◽  
Element Model ◽  
Outer Hair Cells ◽  
Tectorial Membrane ◽  
Linear Superposition

The cochlear amplifier that provides our hearing with its extraordinary sensitivity and selectivity is thought to be the result of an active biomechanical process within the sensory auditory organ, the organ of Corti. Although imaging techniques are developing rapidly, it is not currently possible, in a fully active cochlea, to obtain detailed measurements of the motion of individual elements within a cross section of the organ of Corti. This motion is predicted using a two-dimensional finite-element model. The various solid components are modelled using elastic elements, the outer hair cells (OHCs) as piezoelectric elements and the perilymph and endolymph as viscous and nearly incompressible fluid elements. The model is validated by comparison with existing measurements of the motions within the passive organ of Corti, calculated when it is driven either acoustically, by the fluid pressure or electrically, by excitation of the OHCs. The transverse basilar membrane (BM) motion and the shearing motion between the tectorial membrane and the reticular lamina are calculated for these two excitation modes. The fully active response of the BM to acoustic excitation is predicted using a linear superposition of the calculated responses and an assumed frequency response for the OHC feedback.

scholarly journals Hearing at threshold intensities: by slow mechanical traveling waves or by fast cochlear fluid pressure waves

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Haim Sohmer
Keyword(s):  
Soft Tissue ◽  
Hair Cells ◽  
Traveling Wave ◽  
Basilar Membrane ◽  
Fluid Pressure ◽  
Low Frequency ◽  
Frequency Discrimination ◽  
Outer Hair Cells ◽  
Common Mechanism ◽  
Frequency Stimulation

The three modes of auditory stimulation (air, bone and soft tissue conduction) at threshold intensities are thought to share a common excitation mechanism: the stimuli induce passive displacements of the basilar membrane propagating from the base to the apex (slow mechanical traveling wave), which activate the outer hair cells, producing active displacements, which sum with the passive displacements. However, theoretical analyses and modeling of cochlear mechanics provide indications that the slow mechanical basilar membrane traveling wave may not be able to excite the cochlea at threshold intensities with the frequency discrimination observed. These analyses are complemented by several independent lines of research results supporting the notion that cochlear excitation at threshold may not involve a passive traveling wave, and the fast cochlear fluid pressures may directly activate the outer hair cells: opening of the sealed inner ear in patients undergoing cochlear implantation is not accompanied by threshold elevations to low frequency stimulation which would be expected to result from opening the cochlea, reducing cochlear impedance, altering hydrodynamics. The magnitude of the passive displacements at threshold is negligible. Isolated outer hair cells in fluid display tuned mechanical motility to fluid pressures which likely act on stretch sensitive ion channels in the walls of the cells. Vibrations delivered to soft tissue body sites elicit hearing. Thus, based on theoretical and experimental evidence, the common mechanism eliciting hearing during threshold stimulation by air, bone and soft tissue conduction may involve the fast-cochlear fluid pressures which directly activate the outer hair cells.

Low frequency electromagnetic radiation and hearing

2009 ◽  
Vol 123 (11) ◽  
pp. 1204-1211 ◽  
Author(s):  
J Morales ◽  
M Garcia ◽  
C Perez ◽  
J V Valverde ◽  
C Lopez-Sanchez ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Electromagnetic Fields ◽  
Control Animal ◽  
Guinea Pigs ◽  
Low Frequency ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Morphological Alteration ◽  
Electric Response ◽  
Hearing Level

AbstractObjective:To analyse the possible impact of low and extremely low frequency electromagnetic fields on the outer hairs cells of the organ of Corti, in a guinea pig model.Materials and methods:Electromagnetic fields of 50, 500, 1000, 2000, 4000 and 5000 Hz frequencies and 1.5 µT intensity were generated using a transverse electromagnetic wave guide. Guinea pigs of both sexes, weighing 100–150 g, were used, with no abnormalities on general and otic examination. Total exposure times were: 360 hours for 50, 500 and 1000 Hz; 3300 hours for 2000 Hz; 4820 hours for 4000 Hz; and 6420 hours for 5000 Hz. One control animal was used in each frequency group. The parameters measured by electric response audiometer included: hearing level; waves I–IV latencies; wave I–III interpeak latency; and percentage appearance of waves I–III at 90 and 50 dB sound pressure level intensity.Results:Values for the above parameters did not differ significantly, comparing the control animal and the rest of each group. In addition, no significant differences were found between our findings and those of previous studies of normal guinea pigs.Conclusion:Prolonged exposure to electromagnetic fields of 50 Hz to 5 KHz frequencies and 1.5 µT intensity, produced no functional or morphological alteration in the outer hair cells of the guinea pig organ of Corti.

Stiffness of the Gerbil Basilar Membrane: Radial and Longitudinal Variations

2004 ◽  
Vol 91 (1) ◽  
pp. 474-488 ◽  
Author(s):  
Gulam Emadi ◽  
Claus-Peter Richter ◽  
Peter Dallos
Keyword(s):  
Cross Section ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Sound Waves ◽  
Motion Patterns ◽  
Longitudinal Stiffness ◽  
Longitudinal Variations ◽  
Space Constant ◽  
Qualitative Changes

Experimental data on the mechanical properties of the tissues of the mammalian cochlea are essential for understanding the frequency- and location-dependent motion patterns that result in response to incoming sound waves. Within the cochlea, sound-induced vibrations are transduced into neural activity by the organ of Corti, the gross motion of which is dependent on the motion of the underlying basilar membrane. In this study we present data on stiffness of the gerbil basilar membrane measured at multiple positions within a cochlear cross section and at multiple locations along the length of the cochlea. A basic analysis of these data using relatively simple models of cochlear mechanics reveals our most important result: the experimentally measured longitudinal stiffness gradient at the middle of the pectinate zone of the basilar membrane (4.43 dB/mm) can account for changes of best frequency along the length of the cochlea. Furthermore, our results indicate qualitative changes of stiffness-deflection curves as a function of radial position; in particular, there are differences in the rate of stiffness growth with increasing tissue deflection. Longitudinal coupling within the basilar membrane/organ of Corti complex is determined to have a space constant of 21 μm in the middle turn of the cochlea. The bulk of our data was obtained in the hemicochlea preparation, and we include a comparison of this set of data to data obtained in vivo.

scholarly journals Effects of coiling on the micromechanics of the mammalian cochlea

2005 ◽  
Vol 2 (4) ◽  
pp. 341-348 ◽  
Author(s):  
Hongxue Cai ◽  
Daphne Manoussaki ◽  
Richard Chadwick
Keyword(s):  
Outer Hair Cell ◽  
Basilar Membrane ◽  
Travelling Waves ◽  
Organ Of Corti ◽  
Tectorial Membrane ◽  
Governing Equations ◽  
Element Analysis ◽  
Curvature Effects ◽  
Curvilinear Coordinate ◽  
Cochlear Partition

The cochlea transduces sound-induced vibrations in the inner ear into electrical signals in the auditory nerve via complex fluid–structure interactions. The mammalian cochlea is a spiral-shaped organ, which is often uncoiled for cochlear modelling. In those few studies where coiling has been considered, the cochlear partition was often reduced to the basilar membrane only. Here, we extend our recently developed hybrid analytical/numerical micromechanics model to include curvature effects, which were previously ignored. We also use a realistic cross-section geometry, including the tectorial membrane and cellular structures of the organ of Corti, to model the apical and basal regions of a guinea-pig cochlea. We formulate the governing equations of the fluid and solid domains in a curvilinear coordinate system. The WKB perturbation method is used to treat the propagation of travelling waves along the coiled cochlear duct, and the O (1) system of the governing equations is solved in the transverse plane using finite-element analysis. We find that the curvature of the cochlear geometry has an important functional significance; at the apex, it greatly increases the shear gain of the cochlear partition, which is a measure of the bending efficiency of the outer hair cell stereocilia.

scholarly journals Vibration of the organ of Corti within the cochlear apex in mice

2014 ◽  
Vol 112 (5) ◽  
pp. 1192-1204 ◽  
Author(s):  
Simon S. Gao ◽  
Rosalie Wang ◽  
Patrick D. Raphael ◽  
Yalda Moayedi ◽  
Andrew K. Groves ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Phase Difference ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Lateral Compartment ◽  
Outer Hair Cells ◽  
Supporting Cells ◽  
Tuning Curves ◽  
Cochlear Amplification

The tonotopic map of the mammalian cochlea is commonly thought to be determined by the passive mechanical properties of the basilar membrane. The other tissues and cells that make up the organ of Corti also have passive mechanical properties; however, their roles are less well understood. In addition, active forces produced by outer hair cells (OHCs) enhance the vibration of the basilar membrane, termed cochlear amplification. Here, we studied how these biomechanical components interact using optical coherence tomography, which permits vibratory measurements within tissue. We measured not only classical basilar membrane tuning curves, but also vibratory responses from the rest of the organ of Corti within the mouse cochlear apex in vivo. As expected, basilar membrane tuning was sharp in live mice and broad in dead mice. Interestingly, the vibratory response of the region lateral to the OHCs, the “lateral compartment,” demonstrated frequency-dependent phase differences relative to the basilar membrane. This was sharply tuned in both live and dead mice. We then measured basilar membrane and lateral compartment vibration in transgenic mice with targeted alterations in cochlear mechanics. Prestin499/499, Prestin−/−, and TectaC1509G/C1509G mice demonstrated no cochlear amplification but maintained the lateral compartment phase difference. In contrast, SfswapTg/Tg mice maintained cochlear amplification but did not demonstrate the lateral compartment phase difference. These data indicate that the organ of Corti has complex micromechanical vibratory characteristics, with passive, yet sharply tuned, vibratory characteristics associated with the supporting cells. These characteristics may tune OHC force generation to produce the sharp frequency selectivity of mammalian hearing.

scholarly journals The Role of Prestin in the Generation of Electrically Evoked Otoacoustic Emissions in Mice

2008 ◽  
Vol 99 (4) ◽  
pp. 1607-1615 ◽  
Author(s):  
Markus Drexl ◽  
Marcia M. Mellado Lagarde ◽  
Jian Zuo ◽  
Andrei N. Lukashkin ◽  
Ian J. Russell
Keyword(s):  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Temporal Structure ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Tectorial Membrane ◽  
Wild Type ◽  
Short Delay ◽  
Delay Component

Electrically evoked otoacoustic emissions are sounds emitted from the inner ear when alternating current is injected into the cochlea. Their temporal structure consists of short- and long-delay components and they have been attributed to the motile responses of the sensory-motor outer hair cells of the cochlea. The nature of these motile responses is unresolved and may depend on either somatic motility, hair bundle motility, or both. The short-delay component persists after almost complete elimination of outer hair cells. Outer hair cells are thus not the sole generators of electrically evoked otoacoustic emissions. We used prestin knockout mice, in which the motor protein prestin is absent from the lateral walls of outer hair cells, and Tecta ΔENT/ΔENT mice, in which the tectorial membrane, a structure with which the hair bundles of outer hair cells normally interact, is vestigial and completely detached from the organ of Corti. The amplitudes and delay spectra of electrically evoked otoacoustic emissions from Tecta ΔENT/ΔENT and Tecta +/+ mice are very similar. In comparison with prestin +/+ mice, however, the short-delay component of the emission in prestin −/− mice is dramatically reduced and the long-delay component is completely absent. Emissions are completely suppressed in wild-type and Tecta ΔENT/ΔENT mice at low stimulus levels, when prestin-based motility is blocked by salicylate. We conclude that near threshold, the emissions are generated by prestin-based somatic motility.

scholarly journals Amplification lags nonlinearity in the recovery from reduced endocochlear potential

2020 ◽  
Author(s):  
C. Elliott Strimbu ◽  
Yi Wang ◽  
Elizabeth S. Olson
Keyword(s):  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Basilar Membrane ◽  
Frequency Tuning ◽  
Organ Of Corti ◽  
Endocochlear Potential ◽  
Outer Hair Cells ◽  
Frequency Resolution ◽  
Operating Condition ◽  
Distortion Product

ABSTRACTThe mammalian hearing organ, the cochlea, contains an active amplifier to boost the vibrational response to low level sounds. Hallmarks of this active process are sharp location-dependent frequency tuning and compressive nonlinearity over a wide stimulus range. The amplifier relies on outer hair cell (OHC) generated forces driven in part by the endocochlear potential (EP), the ~ +80 mV potential maintained in scala media, generated by the stria vascularis. We transiently eliminated the EP in vivo by an intravenous injection of furosemide and measured the vibrations of different layers in the cochlea’s organ of Corti using optical coherence tomography. Distortion product otoacoustic emissions (DPOAE) were monitored at the same times. Following the injection, the vibrations of the basilar membrane lost the best frequency (BF) peak and showed broad tuning similar to a passive cochlea. The intra-organ of Corti vibrations measured in the region of the OHCs lost their BF peak and showed low-pass responses, but retained nonlinearity, indicating that OHC electromotility was still operational. Thus, while electromotility is presumably necessary for amplification, its presence is not sufficient for amplification. The BF peak recovered nearly fully within 2 hours, along with a non-monotonic DPOAE recovery that suggests that physical shifts in operating condition are a final step in the recovery process.SIGNIFICANCEThe endocochlear potential, the +80 mV potential difference across the fluid filled compartments of the cochlea, is essential for normal mechanoelectrical transduction, which leads to receptor potentials in the sensory hair cells when they vibrate in response to sound. Intracochlear vibrations are boosted tremendously by an active nonlinear feedback process that endows the cochlea with its healthy sensitivity and frequency resolution. When the endocochlear potential was reduced by an injection of furosemide, the basilar membrane vibrations resembled those of a passive cochlea, with broad tuning and linear scaling. The vibrations in the region of the outer hair cells also lost the tuned peak, but retained nonlinearity at frequencies below the peak, and these sub-BF responses recovered fairly rapidly. Vibration responses at the peak recovered nearly fully over 2 hours. The staged vibration recovery and a similarly staged DPOAE recovery suggests that physical shifts in operating condition are a final step in the process of cochlear recovery.

scholarly journals In vivo optogenetics reveals control of cochlear sensitivity by supporting cells

2021 ◽  
Author(s):  
Victoria Lukashkina ◽  
Snezana Levic ◽  
Patricio Simões ◽  
Zhenhang Xu ◽  
Joseph DiGuiseppi ◽  
...  
Keyword(s):  
Basilar Membrane ◽  
Ex Vivo ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Supporting Cells ◽  
Acoustic Environment ◽  
Cation Conductance ◽  
Fine Control ◽  
Electrical Responses

Abstract Cochlear sensitivity, essential for communication and exploiting the acoustic environment, is due to the sensory-motor outer hair cells (OHCs) that operate in the structural scaffold of supporting cells and extracellular spaces in the cochlear organ of Corti (OoC). It is unclear whether supporting cells (e.g., Deiters cells [DCs] and outer pillar cells [OPCs]) control cochlear sensitivity in vivo. Here we employed optogenetics to measure in vivo sound-induced cochlear mechanical and electrical responses, and ex vivo light-induced DC electrical responses in the OoC of mice that conditionally expressed channelrhodopsins (ChR2) specifically in DCs and OPCs. Illumination activated a nonselective ChR2 cation conductance and depolarized the DCs. This transient action reversibly blocked continuous, normally occurring, minor adjustments of tone-evoked basilar membrane displacements, and OHC voltage responses to tones at and close to their characteristic frequency, and speeded recovery from temporary acoustic desensitization. This is the first direct evidence for the interdependency of the structural, mechanical, and electrochemical arrangement of OHCs and OoC supporting cells which together fine control cochlear sensitivity.

scholarly journals Direct Visualization of Organ of Corti Kinematics in a Hemicochlea

1999 ◽  
Vol 82 (5) ◽  
pp. 2798-2807 ◽  
Author(s):  
Xintian Hu ◽  
Burt N. Evans ◽  
Peter Dallos
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Basilar Membrane ◽  
Mechanical Vibration ◽  
Cell Receptor ◽  
Outer Hair Cells ◽  
Tectorial Membrane ◽  
Low Frequencies ◽  
Geometric Models ◽  
Membrane Vibration

The basilar membrane in the mammalian cochlea vibrates when the cochlea receives a sound stimulus. This mechanical vibration is transduced into hair cell receptor potentials and thereafter encoded by action potentials in the auditory nerve. Knowledge of the mechanical transformation that converts basilar membrane vibration into hair cell stimulation has been limited, until recently, to hypothetical geometric models. Experimental observations are largely lacking to prove or disprove the validity of these models. We have developed a hemicochlea preparation to visualize the kinematics of the cochlear micromechanism. Direct mechanical drive of 1–2 Hz sinusoidal command was applied to the basilar membrane. Vibration patterns of the basilar membrane, inner and outer hair cells, supporting cells, and tectorial membrane have been recorded concurrently by means of a video optical flow technique. Basilar membrane vibration was driven in a direction transversal to its plane. However, the direction of the resulting vibration was found to be essentially radial at the level of the reticular lamina and cuticular plates of inner and outer hair cells. The tectorial membrane vibration was mainly transversal. The transmission ratio between cilia displacement of inner and outer hair cells and basilar membrane vibration is in the range of 0.7–1.1. These observations support, in part, the classical geometric models at low frequencies. However, there appears to be less tectorial membrane motion than predicted, and it is largely in the transversal direction.

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