Semirealistic models of the cochlea (original) (raw)
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BioMed Research International, 2014
The cochlea plays a crucial role in mammal hearing. The basic function of the cochlea is to map sounds of different frequencies onto corresponding characteristic positions on the basilar membrane (BM). Sounds enter the fluid-filled cochlea and cause deflection of the BM due to pressure differences between the cochlear fluid chambers. These deflections travel along the cochlea, increasing in amplitude, until a frequency-dependent characteristic position and then decay away rapidly. The hair cells can detect these deflections and encode them as neural signals. Modelling the mechanics of the cochlea is of help in interpreting experimental observations and also can provide predictions of the results of experiments that cannot currently be performed due to technical limitations. This paper focuses on reviewing the numerical modelling of the mechanical and electrical processes in the cochlea, which include fluid coupling, micromechanics, the cochlear amplifier, nonlinearity, and electrical coupling.
Experimental results in a physical model of the cochlea
Journal of Fluid Mechanics, 1985
Previous contributions made by physical models to the understanding of cochlear mechanics suggested that a new cochlear model should be constructed. This paper illustrates the results obtained with a rectilinear, three-chamber model. The model was geometrically scaled 50: 1 and contained the constituent elements of the cochlear cross-section including the basilar membrane, Reissner's membrane, the tectorial membrane and the organ of Corti. The basilar membrane was stretched crosswise in order to simulate real basilar membrane anisotropy. Two kinds (rigid and elastic) of tectorial membranes were used. The ductus and the sulcus were made visible and the model was also provided with displacement transducers to measure the axial and cross components of the oscillating fluid motion in the scala media. The adoption of a highly flexible membrane, simulating Reissner's membrane, made it possible to vary the viscosity of the scala media compared to that of the other two scalae. The reasons why the simplifications of the previous models were partially rejected and the criteria adopted to assure dynamic similitude between the model and the real cochlea are described in the paper. The results of tests carried out to determine the partial distribution of the amplitude maximum, the phase velocity along the axis of the model and the dispersion curves are shown. The same tests were repeated with partially filled scala vestibuli. Lastly a typical nonlinear feature, that is a continuous flow in the scala media, is described. 362 C. Cancelli, S . D'Angelo, M. Masili and R. Malvano distortions of the acoustic signal (Tonndorf 1970) and to a continuous motion of the fluid from the sulcus to the scala media (Helle 1974b). In addition, the experimental results which Cannel (1969) and Helle (1974a) obtained with physical models have been used by Steele & to prove that the asymptotic method, named WKB, is applicable to fully three-dimensional fluid motion.
Predicting the Effect of Physical Parameters on the Amplitude of the Passive Cochlear Model
The Cochlea plays a crucial role in the hearing of mammalian species including man. The basic function of the cochlea is to map sounds of different frequencies into corresponding characteristic positions on the basilar membrane. Many disciplines meet in the study of the auditory system to understand the truth function of the cochlea. An abnormality or small perturbation in the physical parameters of the cochlea may result a malfunction in the auditory system. In this paper, we developed a mathematical model in the order to show numerically the effect of stiffness and damping on the amplitude displacement in the case of a passive cochlea with the objective to study the ear dysfunction.
Temporal response of a simplified bidimensional numerical model of the cochlea
The Journal of the Acoustical Society of America, 2008
Within the framework of a study related to bone conduction, numerical simulations have been performed in the time domain, with the aim of comparing the cochlear partition displacement in the case of different places of stimulation. An oversimplified 2D model of the cochlea is used. It is first excited with pulses centered on various audible-range frequencies with a localisation of the source which is analogous to the position of the oval window. Secondly, new sets of calculations introduce different localisations and/or spatial extensions of the sources. An analogy with seismology being adequate to simulate the solid-fluid (cochlear partition-perilymph) coupling, a finite difference numerical simulation based upon the Virieux scheme for elastic waves propagation has been used. The movement of the simplified basilar membrane is observable when excited via air or bone conduction. Results of the propagation of a single pulse within the model will be presented and discussed through info...
Cochlear emissions simulated using one-dimensional model of cochlear hydrodynamics
Hearing Research, 1986
Stapes velocity was computed using a nonlinear, one-dimensional model of cochlear hydromechanics. The model's compliances and damping coefficients were mechanically nonlinear and instantaneously varying in proportion to simulated current injected into the cochlea. Experimental data showing the spectral content of the pressure waveform near the eardrum during the delivery of sound and current to the cochlea were compared with model results.
An Immersed Boundary Model of the Cochlea with Parametric Forcing
SIAM Journal on Applied Mathematics, 2015
The cochlea or inner ear has a remarkable ability to amplify sound signals. This is understood to derive at least in part from some active process that magnifies vibrations of the basilar membrane (BM) and the cochlear partition in which it is embedded, to the extent that it overcomes the effect of viscous damping from the surrounding cochlear fluid. Many authors have associated this amplification ability to some type of mechanical resonance within the cochlea, however there is still no consensus regarding the precise cause of amplification. Our work is inspired by experiments showing that the outer hair cells within the cochlear partition change their lengths when stimulated, which can in turn cause periodic distortions of the BM and other structures in the cochlea. This paper investigates a novel fluid-mechanical resonance mechanism that derives from hydrodynamic interactions between an oscillating BM and the surrounding cochlear fluid. We present a model of the cochlea based on the immersed boundary method, in which a small-amplitude periodic internal forcing due to outer hair cells can induce parametric resonance. A Floquet stability analysis of the linearized equations demonstrates the existence of resonant (unstable) solutions within the range of physical parameters corresponding to the human auditory system. Numerical simulations of the immersed boundary equations support the analytical results and clearly demonstrate the existence of resonant solution modes. These results are then used to illustrate the influence of parametric resonance on wave propagation along the BM and explicit comparisons are drawn with results from another two-dimensional cochlea model.
A new computational approach on signal propagation inside the cochlea
2021
Signal propagation inside the cochlea is analyzed from an approximate point of view. This concept has been established by enabling assumptions regarding the feasibility of modeling experiments on the structure of the cochlea in line with the expected results of mathematical models. This article sheds light on reviewing the hearing system from a mathematical, mechanical, electrical, and chemical point of view. This is not to determine which model is better, but to analyze the advancement of the work on cochlear modeling. This paper attempts to present which side of the ear and how the Fourier transformation actually performs its function (seperating complex waves at many frequencies of the sine waves). It provides several improved observations that integrate the effects of the observed studies in such a way that certain characteristics are captured in different types of liner & non-linear modeling in Cochlea, which is considered to be a frequency analyzer existing in the inner ear. O...
A mechano-electro-acoustical model for the cochlea: Response to acoustic stimuli
The Journal of the Acoustical Society of America, 2007
A linear, physiologically based, three-dimensional finite element model of the cochlea is developed. The model integrates the electrical, acoustic, and mechanical elements of the cochlea. In particular, the model includes interactions between structures in the organ of Corti ͑OoC͒, piezoelectric relations for outer hair cell ͑OHC͒ motility, hair bundle ͑HB͒ conductance that changes with HB deflection, current flow in the cross section and along the different scalae, and the feed-forward effect. The parameters in the model are based on guinea-pig data as far as possible. The model is vetted using a variety of experimental data on basilar membrane motion and data on voltages and currents in the OoC. Model predictions compare well, qualitatively and quantitatively, with experimental data on basilar membrane frequency response, impulse response, frequency glides, and scala tympani voltage. The close match of the model predictions with experimental data demonstrates the validity of the model for simulating cochlear response to acoustic input and for testing hypotheses of cochlear function. Analysis of the model and its results indicates that OHC somatic motility is capable of powering active amplification in the cochlea. At the same time, the model supports a possible synergistic role for HB motility in cochlear amplification.
Modes and waves in a cochlear model
Hearing Research, 1980
A tmnplilied model hydroehstle system having many features in common with the cochlea ts studied theoreticafly and experimentally. "/'he system consists of a slet~d~.r rigid tube fiUed w~th a viscous ineotapre~aa'ble fluid. The tube is d~vtded lengthwise into two cl~m~becs (scala vestibuh, scala tympanD by an interior sur[ace, pa~t of wlfi~'h is rigid and part elastic The elastic portion is an i~ottopie plate having variabit; width and ts clamped on its edges. The system ts driven by ,i smusoid,,l input at the stapes end. The mechanical model is 24 times life s~ze and dynamical similarity as mair~rained. Wave i:attems in the plate ate measured using time-ave=~ged and stroboscopic holographic interferometry. At 1~,~ frequency 0~rrespondl~g to less than 500 eycles/s in the cochlea) the response tan be adequately predicted by a one dtmenmoiml theory, The waves art a combination of ttavehng and standing waves. The traveling ,:omponent is solely a dissipative effecL Discrete resonances arc readily observe6 t~ the love frequency range.