Longitudinally propagating traveling waves of the mammalian tectorial membrane

Roozbeh Ghaffari, Alexander J. Aranyosi, Dennis M. Freeman*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    136 Scopus citations

    Abstract

    Sound-evoked vibrations transmitted into the mammalian cochlea produce traveling waves that provide the mechanical tuning necessary for spectral decomposition of sound. These traveling waves of motion that have been observed to propagate longitudinally along the basilar membrane (BM) ultimately stimulate the mechano-sensory receptors. The tectorial membrane (TM) plays a key role in this process, but its mechanical function remains unclear. Here we show that the TM supports traveling waves that are an intrinsic feature of its visco-elastic structure. Radial forces applied at audio frequencies (2-20 kHz) to isolated TM segments generate longitudinally propagating waves on the TM with velocities similar to those of the BM traveling wave near its best frequency place. We compute the dynamic shear storage modulus and shear viscosity of the TM from the propagation velocity of the waves and show that segments of the TM from the basal turn are stiffer than apical segments are. Analysis of loading effects of hair bundle stiffness, the limbal attachment of the TM, and viscous damping in the subtectorial space suggests that TM traveling waves can occur in vivo. Our results show the presence of a traveling wave mechanism through the TM that can functionally couple a significant longitudinal extent of the cochlea and may interact with the BM wave to greatly enhance cochlear sensitivity and tuning.

    Original languageEnglish (US)
    Pages (from-to)16510-16515
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume104
    Issue number42
    DOIs
    StatePublished - Oct 16 2007

    Keywords

    • Cochlear mechanics
    • Dynamic mechanical properties
    • Longitudinal mechanical coupling

    ASJC Scopus subject areas

    • General

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