Re: Cochlea Amplifier models : a new list

[Erik Larsen <elarsen@xxxxxxx>]

There is a dependence of pitch on level, I believe Brian Moore (amongst 
others, probably) has published data on this. I think generally the 
pitch increases somewhat for high-pitched tones (so that goes in the 
right direction, although not by half an octave), and decreases for 
low-pitched tones (as we do not have mechanical measurement for apical 
regions we don't really know what if any shift occurs there at the level 
of the BM). Finally, I believe there is substantial variability in how 
large the perceived shift is between listeners, which indicates it 
probably depends on more than just peripheral effects, if at all.

In general I would not take psychophysical data as evidence for what 
happens in the auditory nerve or on the BM (especially when it comes to 
pitch). There are too many intermediate stages and we don't understand 
all the transformations, so you have to be a bit careful.

I agree with Dick that saturation in the nerve makes this kind of 
comparison between BM and neural tuning more complicated. You would not 
be able just to take 'any data' on level dependence of neural responses. 
Can you specifically give a reference for studies that show neural 
tuning at high sound levels which have in some way controlled for 
response saturation?

Thanks,

Erik

Martin Braun wrote:
> > I haven't been able to find the evidence for the assertion that 
> > neural tuning remains unchanged in some way that differs from the 
> > sense in which BM tuning remains unchanged;
> [.......]
> > Where should I look to study the data on this idea that underlies 
> > your modeling approach?
>
> You can take any data on level dependence of neural responses. None of 
> them mirrors the half-octave shift of BM tuning.
>
> If you have a pure-tone generator, you'll have it even easier. Pull up 
> the sound level from 60 dB to 90 dB. Do you, or don't you, hear the 
> half-octave shift of BM tuning?
>
> Martin
>
> ---------------------------------------------------------------------
> Martin Braun
> Neuroscience of Music
> S-671 95 Klässbol
> Sweden
> web site: http://w1.570.telia.com/~u57011259/index.htm
>
>
>
>
> ----- Original Message ----- From: "Richard F. Lyon" <DickLyon@xxxxxxx>
> To: <AUDITORY@xxxxxxxxxxxxxxx>
> Sent: Wednesday, October 10, 2007 4:46 PM
> Subject: Re: Cochlea Amplifier models : a new list
>
>
> > At 2:54 PM +0200 10/10/07, Martin Braun wrote:
> > > 2) At high sound levels:
> > > Here BM tuning is shifted by about half an octave towards the base 
> > > of the cochlea, whereas neural tuning remains unchanged.
> >
> > I haven't been able to find the evidence for the assertion that 
> > neural tuning remains unchanged in some way that differs from the 
> > sense in which BM tuning remains unchanged; in the BM case, the 
> > location of the maximum moves toward the base; it might be hard to 
> > assess the location of the peak of the neural response, since the 
> > respond rate is pretty compressed near the location of maximum, but 
> > is there data on that?  My impression was that it does not differ in 
> > any significant way from BM tuning; assessing the tuning by phase 
> > response is much easier (e.g., spacing of waveform peaks and PSTH 
> > peaks in response to a click, or waveform autocorr peaks and revcor 
> > peaks in response to a noise).  These do change just a bit with 
> > level, in close agreement with TW models that include appropriate 
> > nonlinearities, e.g. as shown in Kiang's original click data of 1965 
> > and everything subsequently.
> >
> > Where should I look to study the data on this idea that underlies 
> > your modeling approach?
> >
> > Dick

--
Erik Larsen
PhD candidate Speech and Hearing Bioscience and Technology
http://web.mit.edu/shbt

You will stop at nothing to reach your objective, but only because your
brakes are defective.