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Re: mechanical cochlear model

Dear Jonathan, and others,

The mechanisms you described are good candidates for an explanation of the high sensitivity and the good temporal resolution of our ears. They cannot, however, accomplish amplification of a by-passing traveling wave.

This job would be comparable to that of a blind and deaf man standing at a high-way and pushing cars that are passing by at a speed of 80 mph, after having felt each car's air draft.

More importantly, did a traveling wave amplification occur, we would have seen it in our laser data many years ago. Laser interferometry is so sensitive that it instantaneously registers the sightest possible response of outer hair cell (OHC) motor activity. The OHC amplification at the place of characteristic frequency (CF) has been recorded at sound levels as low as 0 dB SPL. At this and even slightly higher levels the basilar membrane remains unmoved between the stapes and the CF place. It did not remain unmoved, if OHC motors would be triggered over this distance.

In conclusion, OHC motor activity amplifies hair cell responses at the CF place, but not a (hypothetical) traveling wave to the CF place.


Martin Braun
Neuroscience of Music
S-671 95 Klässbol
email: nombraun@xxxxxxxxx
web site: http://www.neuroscience-of-music.se/index.htm