Re: Physiological models of cochlea activity - alternatives to the travelling wave

["Richard F. Lyon" <DickLyon@xxxxxxx>]

At 12:57 PM +1000 10/2/07, Matt Flax wrote:
> Current physiologically based models incorporate feedback. Alas a
> majority of them are dependent on the traditional travelling wave
> process. This is not a problem however, I can use the travelling wave as
> a passive mode of input if the research community suggests it is the way

Why would you consider a passive travelling wave, when an active one 
is much better, more plausible, and not hard to model?

> Perhaps the biggest problem with feedback models is that they don't
> specify the physiological correlation between the feedback and the hair
> cell, Organ of Corti nor Cochlea.

You mean there's not a well established micro-mechanical mechanism 
for how the OHCs push back on the BM with an appropriate phase? 
Maybe so, but functionally it's pretty clear what has to be modeled. 
Chuck Steele at Stanford has some credible-looking micro-mechanical 
simulations, as well.

> Here are some feedback models with no physiological basis for the
> feedback :
> a] Zwicker's fantastic model - which begins with the travelling wave [1]
> b] Hopf bifurcation models - which augment the travelling wave. [2] for
>    example.

The Hopf thing (Thomas Duke & Frank Julicher paper) seems to lead to 
a way-too-sharp filter when the gain is high.  With feedback that is 
not highly tuned, not near local oscillation, but with distributed 
amplifiication of the traveling wave, you can get much more 
realistic, not too narrow, filters.  The system can still have 
oscillations, or near oscillations, if points of damage cause 
reflections.

Dick