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Re: from fish to CB

Dear Martin,

Thank you for adding arguments against the old idea of a mechanical traveling wave that transmits energy from the base to the apex of cochlea, defended by Richard Lyon.

Quoting Martin Braun <nombraun@xxxxxxxxx>:

What the hearing antennae of insects do in the air, is what the cilia of
vertebrate hair cells do in the endolymph. Some insects even produce
otoacoustic emissions with their antennae. Apparently for exactly the same
reason as vertebrates do, including humans.

Some years ago, cochlear researchers became aware of these amazing parallels
between insect and vertebrate hearing. And since 2002 they have been
inviting prominent insect researchers to their meetings.

When I mentioned Geoffrey Manley, I intended to remind this stuff. However, mammal hearing is superior. The hair cells exhibit a highly ordered structure with typically three rows of V-shaped bundles of OHCs and tip links at the cilia and other peculiarities. Andrew Bell was perhaps correct when he stressed the role of radial rather than base-to-apex mechanics. Did he not also claim that the hair cells are pressure sensors? Anyway, cochlear function seems to work quite different from what was and is still belived for the transmission line and belonging traveling wave mechanics. You certainly can add a lot of recent results. I only recall a paper where mice with a genetic defect had a partially irregular pattern of haircell bundles but their hearing was not seriously affected. Maybe, such conclusions can be misleading because the auditory system is capable of compensating malfunctions to some extent. Should we expect models of cochlea to mimic this excellence too?

I strongly object to Richard Lyon. Maybe, he was mislead when I argued that the purely mathematical cosine spectrogram is similar to the result from filter banks. This is only correct with respect to the simultaneous, i.e., parallel input instead of serially connected two-ports of a transmission line. While the number of IHCs is limited to about 30 000, and there several auditory nerve fibers projecting to each of them, the cosine spectrogram effectively works continuously with respect to frequency since the sinc-response to an elementary step can be calculated as accurately as necessary.

What about the CB, you will perhaps still adhere to the idea that the brain rather than already the cochlea is reponsible for it. Is there any news from T. Ren? His result was certainly not what Zwislocki and the asymmetrical modelers indended to find out.

Regards,
Eckard




Martin

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Martin Braun
Neuroscience of Music
S-671 95 Klässbol
Sweden
web site: http://w1.570.telia.com/~u57011259/index.htm




----- Original Message ----- From: "Steve Beet" <steve.beet@xxxxxxxx>
To: <AUDITORY@xxxxxxxxxxxxxxx>
Sent: Sunday, October 07, 2007 11:13 PM
Subject: Re: diaphragm output & phase: HC selectivity ... and the lateral
organ of the fish


Ok, I really will keep it short this time!

I may be guilty of over-simplification, but to find more definitive
information about different types of microphone, click, read, and inwardly
digest everything at this URL:

http://en.wikipedia.org/wiki/Microphone

Steve Beet