Re: mechanical cochlear model

[Martin Braun <nombraun@xxxxxxxxx>]

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

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