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Re: AUDITORY Digest - 7 Oct 2002 to 8 Oct 2002 (#2002-168)

Dear Auditory,

I would like to make one very obvious point, only because I have not seen
it explicitly stated.

High frequency neurons phase lock just as well as low frequency neurons.
It is just that neurons (regardless of place) do not phase lock to high
frequency tones. Rather they phase lock to modulations.
I am not saying that anyone is confused on this rather obvious point,
I rather want to be sure there is no misunderstanding
of the difference between place and frequency.

Repeating myself:

All neurons, up and down the BM, phase lock equally, to frequencies
up to 4.5 kHz.

I am sure there are better references than this, but here is a good
place to start:

  author = {Allen, J. B.},
  title = {Magnitude and phase-frequency response to single tones in the
       auditory nerve},
  journal = JASA,
  volume = {73},
       number = 6,
  pages = {2071-2092},
  year = {1983}

Jont


Date:    Tue, 8 Oct 2002 08:59:13 +0200
From:    Eckard Blumschein <Eckard.Blumschein@E-TECHNIK.UNI-MAGDEBURG.DE>
Subject: Re: pitch neurons

At 11:29 07.10.2002 -0400, Allen G Lindgren wrote:


Eckard
Can you elaborate on "Merely below about 1kHz,


synchrony can be very high.".


Yes I can:
I wrote:


On average, ten auditory nerve fibers cooperate statistically with just
one inner hair cell. Each fiber is bound to refractory time. So roughly
speaking, all ten together cannot continuously phase lock with intervals
smaller than a tenth of refractory time. Merely below about 1kHz,
synchrony can be very high.
This limitation due to statistic time sharing does, however, not exist
immediately after nearly all fibers reached a state of readiness for
firing.
Given frequency of modulation or rate of clicks is low enough for that,
then the stationary upper frequency limitation is much less relevant
for the whole temporal structure, including interaural envelope delay
(IED), during a split millisecond of adaptation.


I refer to Eric D. Young who wrote chapter 4 of 'Synaptical Organization
of the Brain'. Fig. 4.11 shows synchrony in the ANF not much deviating
from the value 0.8 up to 1 kHz but then increasingly dropping and
reaching zero at 4.5 kHz. Merely synchrony of so called primarylike VCN
neurons can approach the value one.
We realize these limitations like the optimal ones if we understand how
the random cooperation of the ten fibers works. Albert Einstein said:
'God does not play dice'. With respect to causality he was probably correct.
However, we have to learn that stochastic cooperation of neurons must not
be ignored.
Forget the illusion that Gammatone filters adequately describe what happens.




--
Jont B. Allen,     jba@auditorymodels.org;   908/654-1274voice; 908/789-9575 fax
382 Forest Hill Way
Mountainside NJ 07092
http://auditorymodels.org/jba

``A paradox is simply an error out of control''
  --E.T. Jaynes, Chapter 15 of http://bayes.wustl.edu/etj/prob/