the liver and the brain

David Longley David at longley.demon.co.uk
Wed Sep 1 17:24:41 EST 2004


In article <363d693e.0409011341.136978f5 at posting.google.com>, ray 
scanlon <rscanlon at nycap.rr.com> writes
>The motor program generators are established in the developing nervous
>system by the DNA. When triggered, they produce motor activity. We
>ask, "How are they triggered?"
>
>The sensory neurons transduce the energy of the universe as it arrives
>at the body surface. They also transduce energy from the internal
>condition of the body. The resultant signal energy filters through the
>interneurons and, when it summates at a given motor program generator,
>it triggers the generator.
>
>The paths that the signal energy traverses are originally set up by
>the DNA. I emphasize that the nervous system is precisely connected
>before and after birth to be prepared to handle an unfriendly universe
>that previous generations encountered. When the organism meets up with
>the present milieu, there is a tremendous pruning and die-off of
>synapses and neurons.
>
>There is a reorganization of synapses (called learning by some) as the
>organism masters the location of food and water sources and the
>position of secure resting places. Later there is the problem of
>mates. The paths through which the signal energy passes are altered so
>that the appropriate motor program generators are triggered so as to
>ensure survival.
>
>First place is given to avoidance of the predator.
>
>Ray

Some (not all) of the above I have no quarrel with. What makes no sense 
to me is that you neglect or oppose 1) operant behaviour and 2) operant 
conditioning in preference for talk about CPGs etc in incredibly complex 
systems when such talk actually seems to be based upon operants (either 
explicitly or tacitly based).

I've said before that (in mammals and other higher animals) there are 
interneurones at the primary synapses (just think of the dorsal and 
ventral horns of the spinal cord) and that you'd be wiser to think of 
what happens at subsequent levels (secondary, teritary synapses etc) as 
progressive elaboration of (say defensive) behaviour. As one goes deeper 
into the CNS (from receptor surfaces) behaviours become a) more 
temporally remote from the initial receptor stimulation and therefore b) 
more behaviourally "elaborated" and presumably c) therefore more 
extended in time/complexity.

Beyond, say, the teritary level it all gets (at the afferent level) 
rather polysensory (and by implication, just as complex in terms of 
efferent response integration/elaboration too). That is, it gets 
fiendishly complicated. This is one of the reasons why I keep lamenting 
that even at the post thalamic level it still tends to be anyone's game 
and why I'm suspicious of grandiose claims about what's going on in "the 
mind" or even in "CPGs", given how little we currently know about the 
302 nerve net of the 1mm long nematode Caenorhabditis elagans never mind 
Drosphila, Aplysia, let alone pigons or rats.

We do know something about behaviour.

I've said before of course (in posts to c.a.p over the years). You've 
either ignored them or you just don't like them. Why?
-- 
David Longley



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