Re: Rationale for Critical Bands

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

I'm still unclear on Ehret's point of view on 
this critical band in ICC and its level 
dependence or not.  The 1988 quotes don't clarify 
a lot.

I still haven't been able to find the basis for 
this statements that the critical band he finds 
in ICC is level independent.  His own 1985 figure 
with Merzenich seems to contradict the idea that 
CB is level independent.  See 
http://dicklyon.com/tech/Scans/Ehret_data.png 
where I fitted the high-level and low-level 
points separately, and got lines spaced apart by 
a half octave and more between them, sort of like 
CB in the periphery.  There's too much noise in 
the data to draw any strong conclusion, but 
certainly the data doesn't support the idea that 
this measure of bandwidth of level independent.

I have no quibble with Ehret's statement that 
"The regression line gives a good approximation 
of average neuronal critical bandwidths valid for 
the whole tested intensity range."  That is, it's 
an OK level-independent approximation; such 
approximations are commonly done, and not unique 
to ICC.

As to "the critical band analysis must arise in 
higher auditory brain centers," that may be true 
for what he's describing here as "the critical 
band analysis".  I'm not convinced it has a lot 
to do with what's usually called critcal bands, 
which are on the order of 1/4 to 1/3 octave over 
most of the auditory range.  Nearly half of 
Ehret's data are over 1 full octave, and there's 
huge scatter.  It really seems like a different 
beast.

The other p.140 quote also sounds sensible, but 
not clearly relevant to the discussion.

I'd still like to see what he published in 1995 
and referenced for the conclusion of constancy 
with level.

Dick



At 9:34 PM +0200 6/23/10, Martin Braun wrote:
> Dear Dick and other,
>
> You need not find the proceedings of the 1994 
> Irsee conference. Ehret's (and Merzenich's) work 
> on CB related observations in the ICC of the cat 
> is completely documented in a comprehensive 
> review from 1988:
>
> http://www.ncbi.nlm.nih.gov/pubmed/3289688
>
> Here you find many neuronal tuning curves which 
> show you a level independence over large level 
> ranges. Further, as to the authors' opinion on 
> your question, you might like to read the 
> following three quotes from this review:
>
> "It is suggested that the critical band analysis must arise in
> higher auditory brain centers." (p. 140)
>
> "This convergence of input on a single map of frequency representation in
> the ICC can be expected to give rise  to coding of critical band
> characteristics which lack an explanation by neuronal responses at
> lower levels." (p. 140)
>
> "The critical bandwidth, of which in 1970 J.V. Tobias said in the foreword
> to Scharf's chapter on critical bands
> '..... the other senses lack the mysteriousness 
> of this unseen - perhaps nonexistent - but 
> pervasive auditory filter',
> would exist in the functional anatomy of the 
> central nucleus of the IC." (p. 160)
>
> Why it is the anatomy of the ICC, which is 
> unique in the brain concerning its CB 
> relatedness, is described in the work of 
> Langner, Schreiner, and Braun, which I have 
> already referenced twice in this thread.
>
> Martin
>
>
> ---------------------------------------------------------------------
> Martin Braun
> Neuroscience of Music
> S-671 95 Klässbol
> Sweden
> email: nombraun@xxxxxxxxx
> web site: http://www.neuroscience-of-music.se/index.htm
>
>
>
> ----- Original Message ----- From: "Richard F. Lyon" <DickLyon@xxxxxxx>
> To: <AUDITORY@xxxxxxxxxxxxxxx>
> Sent: Wednesday, June 23, 2010 7:34 PM
> Subject: Re: Rationale for Critical Bands
>
> > A follow-up, in case anyone still cares...