AW: Cochlea Amplifier models : a new list

["reinifrosch@xxxxxxxxxx" <reinifrosch@xxxxxxxxxx>]

Hello Matt and List,

This one-man show is going to end soon now, I hope.
I insert some answers below.

----UrsprÃngliche Nachricht----
Von: flatmax@xxxxxxxx
Datum: 19.10.2007 03:00
An: <AUDITORY@xxxxxxxxxxxxxxx>
Kopie: "reinifrosch@xxxxxxxxxx"<reinifrosch@xxxxxxxxxx>
Betreff: Re: Cochlea Amplifier models : a new list

>Robles [1] Figure 14 - Phase increases away from stapes
>... agreed. 

Phase decreases, so the wave travels from base 
towards apex.

>I have no problem with Bekesey's PASSIVE
>travelling wave... it is a good thing he won a Nobel peace
>prize for it ... in my opinion. To us he is like Newton.
>Would you agree ? A g-dfather of Auditory physics.

Yes, I think both Sir Isaac and von BÃkÃsy were creative,
energetic and courageous. Nevertheless, I'd like to ask
the List a question (which is only weakly related to the
present cochlear-amplifier discussion): On page 443
of his book "Experiments in Hearing" von BÃkÃsy
mentions "the gelatinous mass of the cochlear duct".
Was that the TM?

>Ren [2] Figure 2 - BM motion and emissions have roughly
>the same phase and same delay. The activity in the
>cochlea - with respect to DPOAEs and other OAEs - are
>as fast (or slightly faster depending on tonotopic 
>location) as the travelling wave. Indeed it is now emerging
>that apical emissions are quite likely FASTER !

I just re-read T. Ren, W. X. He, and A. L. Nuttall (2006),
"Backward propagation of otoacoustic emissions in the
cochlea", in "Auditory Mechanisms", A.L. Nuttall et al., eds.,
World Scientific, New Jersey, etc.: 79-85.
They conclude:"[...] This result supports the cochlear-fluid-
compression-wave model and not the backward-travelling-
wave theory".

Remember that fast (1500 m/s) compressional waves
exist also, e.g., during ordinary exposures of the cochlea
to sine tones. These waves have large wavelengths,
no significant across-BM liquid-pressure difference, and thus
yield no signals from the IHC's to the brain. Compressional
waves can, however, travel from the cochlea to a 
microphone in the ear canal and be registered there.

"My" model is therefore not affected by the otoacoustic-
emission work by Ren et al., I believe.

>... I believe that Ren questions whether energy is 'fed into'
>the travelling wave ... particularly in his later paper these
points become more clear [3].

The fact that in a healthy cochlea energy is fed, by OHC's 
in the basal half of the active-peak x_b-region, into the TW, 
is proven, in my opinion, e.g. by the mentioned papers
of Kolston (2000) and de Boer and Nuttall (1999).

Reinhart Frosch.

Reinhart Frosch,
Dr. phil. nat.,
r. PSI and ETH Zurich,
Sommerhaldenstr. 5B,
CH-5200 Brugg.
Phone: 0041 56 441 77 72.
Mobile: 0041 79 754 30 32.
E-mail: reinifrosch@xxxxxxxxxx .