Q about artificial and biological neural-nets

Charles D. Nichols cn0p+ at andrew.cmu.edu
Mon Mar 1 09:31:58 EST 1993


>From: lamontg at u.washington.edu
>Subject: Re: Q about artificial and biological neural-nets
>Date: 1 Mar 1993 00:06:19 GMT
 
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>a *hypothetical* consideration that i've got is that this could be
>functional, especially given the fact that its stimultaing changes in the
>5-HT system.  the 5-HT system is one that pretty much stops modifying
>its connections after adolescence (i've got a reference on this somewhere --
>"the sleeping giant" and "seritonergic" are title keywords to check i
>think...).  so, the "damage" may be more than offset by stimulating
>axonal growth and possibly by wiping out some dysfunctional connections
>which do not grow back...

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This is an interesting hypothesis.  I have recently read about
reorganization of the adult macquaq(sp?) somatasensory cortex, and would
assume that this would be similar to reorganization of a neural net
after selective destruction by a neurotoxin.  The damage done to the
5-HT system after selective destruction by phenethylamines does not (to
my knowledge) really produce radical enough damage to test
reorganization.  A majority of the synaptic terminals that are
eliminated are thought to re-establish connections with the same
neurons.  You would need a functionally defined neural system to test,
such as the visual system, or possible LTP systems.  A good test might
be to find a toxin specific for neurons in the visual cortex, like MDA
is for the 5-HT system, and admintister it to an animal raised to
adulthood in the dark.  Then during recovery from the toxin, present
visual stimuli to the animal and compare visual performance to a control
animal who was not presented with the toxin.  (You could even throw in a
couple trophic factors to stimulate nerve growth!). However, I don't
know of any visual toxins. 

Chuck



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