[Comp-neuro] Review announcement

Ali Minai minai_ali at yahoo.com
Wed Jul 23 14:52:24 CEST 2008


I would add to this the ideas recently advanced by Izhikevich and Hoppensteadt (among others) that subthreshold oscillations can effectively multiplex signals so that different sub-populations of neurons only respond to spikes that occur near the peaks of their oscillations. Of course, one still has to explain how various sub-populations come to have their own synchronized sub-threshold oscillations in the first place, but it is an interesting mechanism. I certainly agree with Bard Ermentrout that neural oscillations are too ubiquitous a phenomenon to be left unexploited by evolution. Neil Burgess already pointed out one potential function in the hippocampus. Also, what about a simple sequencing function? Walter Freeman talks about a neural "shutter", and some sort of "clocking" is implicit in many models of cognitive function.

Ali


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Ali A. Minai
Associate Professor
Associate Head for Electrical Engineering
Department of Electrical & Computer Engineering
University of Cincinnati
Cincinnati, OH 45221-0030

Phone: (513) 556-4783
Fax: (513) 556-7326
Email: aminai at ececs.uc.edu
          minai_ali at yahoo.com

WWW: http://www.ececs.uc.edu/~aminai/

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--- On Tue, 7/22/08, G. Bard Ermentrout <bard at math.pitt.edu> wrote:
From: G. Bard Ermentrout <bard at math.pitt.edu>
Subject: Re: [Comp-neuro] Review announcement
To: 
Cc: comp-neuro at neuroinf.org, comp-neuro-bounces at neuroinf.org
Date: Tuesday, July 22, 2008, 3:22 PM

For what it is worth - I have puzzled over the ubiquity of oscillations in 
the CNS and still wonder what they are good for. Jim and others argue 
epiphenomena, and this could still be correct, but it is real hard for me 
to believe that nature would ignore a free byproduct like this.  One thing 
about oscillations is that they have associated with them a zero 
eigenvalue at the single cell, microcircuit or other level and what this 
does is it makes it very eay to modulate the timing of their spikes. Much 
more so than with fixed points. Thus it very easy from the point of view 
of efficiency to move the spikes around in sych a way as to e.g. compute 
correlations via the stochastic synchrony mechanism and thus propagate 
feedfoward synchronous or correlated activity to other areas or layers. 
Synchrony or near synchrony is very efficient at propagating in 
feedforward networks.  Oscillations make it real easy to read out 
correlations and also make it very easy to quickly desynchronize groups 
with simple modulation of their intrinsic dynamaics - e.g. ACh  which can 
greatly affect how a neuron responds to the timing of an input and to 
other neurons to which it is attached.

>From Rome with one vino too many,

bard Ermentrout

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