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Published on: August 18, 2020
The cortilymph wave: Its relation to the traveling wave, auditory-nerve responses, and low-frequency downward glides
1Eaton-Peabody Lab, Mass. Eye and Ear, 243 Charles St., Boston MA 02114, USA; Harvard Medical School, Dept. of Otolaryngology Head and Neck Surgery, Boston MA, USA.
Abstract:
In the cochlear base, recent data show that amplification of the traveling wave does not come from outer-hair-cell (OHC) forces acting on the basilar membrane (BM). Instead, traveling wave amplification is hypothesized to come from OHCs producing cyclic cortilymph flow along the organ-of-Corti (OoC) tunnels (the "cortilymph wave"), which changes OoC cross-section area and adds energy to the scala-media-fluid traveling wave. This hypothesis accounts for amplification of cochlear-motion in the base but may not work in the low-frequency apex. One base-to-apex difference is the OHC-membrane resistance-capacitance (RC) low-pass filter. Measurements in live animals found the OHC-RC corner frequency, Fc, was ∼3 kHz. At tone frequencies >>Fc, the RC filter delays the cortilymph wave from the traveling wave by ¼ cycle, which provides the correct timing for OoC-area-change traveling-wave amplification. However, at frequencies <
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