Numerical Analysis of a Nonlinear Mechanical-Electrical-Acoustical Model of the Cochlea

Cochlear Mechanics;Auditory System;Acoustics;Mechanical Engineering;Engineering;Mechanical Engineering

Nankali, AmirPopa, Bogdan Ioan ;

University of Michigan

关键词: Cochlear Mechanics;    Auditory System;    Acoustics;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/144086/nankali_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The overarching goal of my research project is to develop a computational model of the mammalian auditory system and compare the results with the experimental data. This model describes the response of the cochlea to both external acoustic and internal electrical stimulations. The cochlea is the spiral-shaped part of the inner ear where the fluid-borne vibrations are detected by the auditory sensors and then the information, in the form of neural signals, are transferred to the brain by the auditory nerves. The cochlear model will enhance our understanding of failure mechanisms in the cochlea, answering important questions as to the morphological elements of the cochlea that fail and why. A mathematical model of the cochlear response to sound over the entire spectrum will help us understand how important classes of signals are processed in the cochlea (such as speech and music) which can lead to better speech processing algorithms or cochlear implant electrical stimulation paradigms. One important question of biophysics of the cochlea is the underlying mechanism of the cochlear active process which enables sound processing over a broad range of frequencies and intensities. Two mechanisms are hypothesized as the main active processes: outer hair cell (OHC) somatic electromotility and hair bundle (HB) motility. The proposed active mechanisms are implemented into our model and their relative contribution on the cochlear nonlinear amplifier is investigated. It is shown that somatic based activity plays a fundamental role in amplification while the HB motility contribution remains elusive. Two distinct mechanisms are identified through which the HB activity affects the cochlear dynamics. The extracellular voltage is shown to undergo a phase shift at frequencies slightly below the peak, that coincides with the onset of the nonlinear amplification. It is hypothesized that this phase difference between the electrical and mechanical responses gives rise to effective power generation of the OHC somatic force. A three-dimensional model of the cochlea is utilized along with experimental data and it is shown that the electro-mechanical phase transition, generated by the tectorial membrane (TM) shear mechanics, activates the cochlear nonlinear amplifier.The cochlear computational model is also used to simulate a series of active in vitro experiments and interpret the results. It is shown that our model of the electrical, mechanical, and acoustical conditions of the experimental configuration is able to replicate the important findings of the experiments while our interpretation of the results contradicts conclusion of the experiments. It is shown that the OHC somatic electromotility, rather that HB motility, is sufficient to predict the nonlinearities observed in the experiments.