title: Coupling active hair bundle mechanics, fast adaptation, and somatic motility in a cochlear model.
abstract: One of the central questions in the biophysics of the mammalian cochlea is determining the contributions of the two active processes, prestin-based somatic motility and hair bundle (HB) motility, to cochlear amplification. HB force generation is linked to fast adaptation of the transduction current via a calcium-dependent process and somatic force generation is driven by the depolarization caused by the transduction current. In this article, we construct a global mechanical-electrical-acoustical mathematical model of the cochlea based on a three-dimensional fluid representation. The global cochlear model is coupled to linearizations of nonlinear somatic motility and HB activity as well as to the micromechanics of the passive structural and electrical elements of the cochlea. We find that the active HB force alone is not sufficient to power high frequency cochlear amplification. However, somatic motility can overcome resistor-capacitor filtering by the basolateral membrane and deliver sufficient mechanical energy for amplification at basal locations. The results suggest a new theory for high frequency active cochlear mechanics, in which fast adaptation controls the transduction channel sensitivity and thereby the magnitude of the energy delivered by somatic motility.
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, USA. jmeaud@umich.edu
authors.forename: Julien
authors.initials: J
authors.lastname: Meaud
authors.forename: Karl
authors.initials: K
authors.lastname: Grosh
mesh_terms: D000161:Acoustic Stimulation; D000222:Adaptation, Physiological / Q000187:drug effects; D001489:Basilar Membrane / Q000166:cytology / Q000187:drug effects; D001696:Biomechanical Phenomena; D002118:Calcium / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects; D004553:Electric Conductivity; D018072:Hair Cells, Auditory, Outer / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D006309:Hearing / Q000187:drug effects / Q000502:physiology; D055595:Mechanical Phenomena; D040542:Mechanotransduction, Cellular / Q000187:drug effects; D008954:Models, Biological; D020156:Salicylic Acid / Q000494:pharmacology; D013997:Time Factors
chemical_list: D020156:Salicylic Acid; D002118:Calcium