Nonlinear Amplification Mechanism In Auditory Perception

It is generally accepted that mammalian hearing is greatly enhanced by mechanical amplification.Hair cells are also thought to predetermine certain phenomena in hearing,such as active amplification,nonlinear compression of dynamic range,sharp frequency selectivity,and generation of spontaneous emissions.An active process of mechanical energy growth is proposed to account for these nonlinear features.However,what is the precise nonlinear behaviors in hearing,how the mechanical amplification occurs,and from where the active force derives have not yet been determined.This work has made a clear understanding of the active amplification by the physical methods,especially the energy conversion and Lagrange mechanics.We analyze the nonlinear dynamic equations and their behaviors which judged these nonlinear characteristics may be resulting from a velocity-dependent active force.Then,we adopt an energy method to identify the mechanical work of hair cell during its mechanoelectrical transduction(MET),by which a transduction force is inferred according to electricity consumption.The result reveals the velocity-dependent active force comes from the hair bundle,which has not been observed directly,matches the active force described in a typical Hopf amplification.Finally,an equation of entire hair cells is established and analyzed through extended Lagrange mechanics,a generalized energy method for complex systems with electrical and mechanical activities.The governing equations with mechanoelectrical transduction(MET)and electromotility which accurately describe the effect of nonlinear amplification in outer hair cells.According to the research,this article reveals the active mechanism of auditory amplification on a subcellular level,which provides a basis for the mechanism of hearing impairment and hearing disorders.