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Re: BM motion
Conventional traveling-wave theory does account for high-side suppression.
In an active cochlea, as the traveling wave approaches its best location,
it is amplified over a region basal to the peak. If the suppression tone
excites this basal region, it will interfere with the amplification
process.
For more information on the spatial extent of high-side suppression, see:
Javel E, Geisler CD, Ravindran A.
Two-tone suppression in auditory nerve of the cat: rate-intensity and
temporal analyses J Acoust Soc Am. 1978 Apr;63(4):1093-104.
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David C. Mountain, Ph.D.
Professor of Biomedical Engineering
Boston University
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On Wed, 14 Nov 2007, Matt Flax wrote:
> Hi list and Richard,
>
> Travelling waves have no mechanism for high side suppression...
> it is simply not possible.
>
> Clearly in the literature [1] last paragraph for example ... here
> is an excerpt :
> ... neither models nor experiments have yet answered what
> is perhaps the central question of mammalian cochlear
> physiology, namely, the origin of the CF specificity of
> two-tone suppression and other mechanical nonlinearities.
>
> I have other references.
>
> [1]
> @ARTICLE{Ruggero:1992,
> author = {Ruggero, M.A. and Robles, L. and Rich, N.C.},
> title = {Two-tone suppression in the basilar membrane of the cochlea:
> mechanical
> basis of auditory-nerve rate suppression},
> journal = {Journal of Neurophysiology},
> year = {1992},
> volume = {68},
> pages = {1087-1099},
> number = {4},
> month = {October}
> }
>
>
> On Tue, Nov 13, 2007 at 08:22:06PM -0800, Richard F. Lyon wrote:
> > No matter how the nonlinearity affects the tone amplitudes, the sum of two
> > sinusoids of different frequencies is easily distinguishable from a larger
> > single sinusoid, through the temporal pattern, which will be appararent in
> > the auditory nerve firing-time patterns, even when both frequencies are
> > higher than can be coded by synchrony.
> >
> > As to the nonlinearity, it shows up clearly in the mechanics, when the OHCs
> > are functioning, and it's not hard to see how OHCs in one region can change
> > the response to other tones that travel through that region to be localized
> > further on; that is, how high-f can suppress low-f if not too much lower.
> > The other direction works slightly differently, but the key is that
> > different frequencies share the same traveling wave medium that amplifies
> > them, so you get suppression. There may yet be mysteries in the
> > micromechanical details, but not in the overall functional effect.
> >
> > Matt, is the "'frequency specificity' mystery" something that you find in
> > the literature? Or do you just mean you haven't found a clear enough
> > explanation?
> >
> > Dick
>
> --
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