Definitive tests of Bell resonance theory? (Christopher Shera )

Subject: Definitive tests of Bell resonance theory?
From:    Christopher Shera  <shera(at)EPL.MEEI.HARVARD.EDU>
Date:    Mon, 10 Jul 2000 10:19:46 -0400

Andrew, In describing your resonance theory you write... > I have sought to ... develop a true > resonance theory in which outer hair cells sense the common-mode pressure in > the cochlea. [The theory] calls on the body of the OHCs to respond to fast > intracochlear pressure and in reacting (OHC2 in-phase to pressure; OHC1&3 in > antiphase to pressure) to create a surface acoustic wave (SAW) resonator. [...] > [As a result] it is the fast compressional wave that sets up a pressure regime > in the cochlea which launches more slowly evolving wave activity. To the extent that I understand all this, I believe that a definitive test of this hypothesis has already been performed; the results appear to contradict your model. In their paper "Is the pressure difference between the oval and round windows the effective acoustic stimulus for the cochlea?" (JASA 100:1602-1616), Voss et al. compare cochlear potential responses to common- and difference mode pressure inputs at the oval and round windows. They find that the response to the pressure difference mode is approximately 2 orders of magnitude larger than the response to the common mode (with the limit set in large part by limits in their ability to measure extremely small pressure differences). Naively, at least, this seems to contradict your model, which suggests that the common pressure mode within the cochlea constitutes the effective stimulus to the ear. You also write... > If OHCs are pressure detectors, it follows that they must possess > some compressibility. In their ARO abstract (1996, #227), Ravicz et al. measure the compressibility of the cochlea. Their results are consistent with the known compressibility of water. Of course, these measurements were performed in a temporal bone preparation, so their applicability to the living ear is uncertain. Whether or not they contradict your model depends on the mechanism by which the OHCs are supposed to compress and on what the value of their compressibility is predicted to be. Perhaps you can address these issues in your submission to JASA. -Christopher Shera -- Christopher Shera 617-573-4235 voice Eaton-Peabody Laboratory 617-720-4408 fax 243 Charles Street, Boston, MA 02114-3096 "Sadism and farce are always inexplicably linked." -- Alexander Theroux

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