Modulation of Neuronal Output

Kevin Hellman kevin at jackson.head.neurology.wisc.edu
Wed Jul 6 18:45:36 EST 1994


In article <2ves5r$h0d at vixen.cso.uiuc.edu> kspencer at iti.org (Kevin Spencer) writes:

   Path: news.doit.wisc.edu!saimiri.primate.wisc.edu!ames!elroy.jpl.nasa.gov!usc!howland.reston.ans.net!vixen.cso.uiuc.edu!kspencer
   From: kspencer at iti.org (Kevin Spencer)
   Newsgroups: bionet.neuroscience
   Date: 6 Jul 1994 18:12:11 GMT
   Organization: UIUC Department of Psychology
   Lines: 40
   References: <2vearl$klc at portal.gmu.edu>
   NNTP-Posting-Host: p300.cpl.uiuc.edu

   herwin at mason1.gmu.edu (HARRY R. ERWIN) writes:


   >There is a slowly developing consensus that semantics in the brain is
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   >carried in the synchronization of pulse trains, whose amplitude reflect
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   >local levels of activation. This may be at the level of individual cells
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
   >or neural masses. Walter Freeman has a partial model of how this can
   >occur at the level of neural masses--sparse nerve cell assemblies (NCAs,
   >my 'activation networks') when suitably activated enter a second mode
   >dynamic (periodic in isolation, chaotic when interactive) that modulates
   >the local level of activation. The difficulty with this model is that
   >the modulation has to be multiplicative; if it is additive, the second
   >mode dynamics swamp the local activation level or viceversa. Has anyone
   >identified a mechanism for multiplicative interaction between neurons or
   >neural masses? Is stochastic resonance a candidate?

   >Please note that I may have garbled Freeman's model.

   >--
   >Harry Erwin
   >Internet: herwin at gmu.edu 
   >Just a dumb engineer working on Katchalsky nets....

   Don't you think it's rather premature at this stage of computational
   neuroscience to presume that we know *anything* about something as high-
   level as "semantics"?  Freeman and others are doing very important work
   in understanding the dynamics of neural systems, but I find it hard to
   believe that the dynamics of the olfactory bulb are likely to be similar
   to the dynamics underlying human cognition.  We simply don't know enough
   yet.

   -----------------------------------------------------------
   Kevin Spencer
   Cognitive Psychophysiology Laboratory and Beckman Institute
   University of Illinois at Urbana-Champaign
   kspencer at p300.cpl.uiuc.edu / kspencer at psych.uiuc.edu
   -----------------------------------------------------------
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Although you might think computational neuroscience does not have the 
neccessary parameters to conduct a simulation about semantics, there
has been significant progress along the understanding of hebbian learning.

Long Term Potentation, although the mechanisms are not well understood,
seems to be quite promising.  It can be found just about everywhere, 
including piriform cortex!  Why do you singe single out the Olfactory 
bulb?  Freeman's work was less on cognition in the olfactory bulb, but
on epileptogensis.  Although, I do neurosimulation at UW I cannot speculate
on how much we really do know, but overall, I am quite impressed.  There
is room for improvement and time for us-- the Neurosimulators.

*****************************************************
KEVIN HELLMAN		kevin at head.neurology.wisc.edu 
*****************************************************
LAB: (608)-263-5343     University of Wisconsin
                        Neurology & Neural Simulation
*****************************************************


--
*****************************************************
KEVIN HELLMAN		kevin at head.neurology.wisc.edu 
*****************************************************
LAB: (608)-263-5343     University of Wisconsin
                        Neurology & Neural Simulation
*****************************************************



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