the liver and the brain
rscanlon at nycap.rr.com
Sat Sep 4 05:31:22 EST 2004
Dan Michaels writes:
> r norman writes:
> > The question is: how much of the improvement of performance after
> > birth is due simply to the continued development and maturation of the
> > nervous system, that is, to the further elaboration of the genetic
> > program that was left incomplete at birth, and how much to actual
> > learning and experience? My guess is that for many truly altricial
> > animals both aspects are important and it is a very difficult
> > experimental question to sort out which component is more important.
> > More likely, in many mammals (especially primates and humans) the
> > genetic program is preconfigured to require learning as an integral
> > component.
Lord knows, I have said things in this debate that I wish I hadn't,
but I will
open my big mouth again. I sincerely apologize to anyone whose
feelings were hurt.
In my opinion, possibly we should ask ourselves whether we wish to
assign causal powers to the soul. If we wish to differentiate between
"further elaboration of the genetic program" and "actual learning",
this may be the case.
These are not idle words. Stephen Jay Gould, in his great battle with
the creationists, would distinguish between the two magisteria, that
of science and that of religion. There is no final answer, but we can
always take temporary positions.
I would say that if the subject is the scientific explanation of the
brain, then we couldn't distinguish between "genetic program" and
"learning". But this is only my temporary position. Outside the
laboratory, I am a religionist. ("Lab" is a figure of speech. All I
have is an electronics workbench in the basement.)
Some say you can be pc in the lab, but I say not. I say the genetic
program constructs a brain that is plastic, that has rules of synaptic
modification designed to meet an unfriendly universe and adjust to it.
Otherwise, the species should disappear.
This is only my temporary position.
> BTW, I'm sure your answer is pretty much "the" answer. But actually
> there might be 3 parts to look at - genetics, development [ie, as in
> finetuning of the type Hubel+Wiesel studied in lid-sutured animals],
> and learning [as in finally learning to distinquish a cat from a
> lion]. My personal working-hypothetical model pretty much allocates
> the latter learning parts to areas beyond the 30+ visual centers of
> the cortex, which mainly function as visual pre-processors with more
> or less specific functions in each. The outputs of these form the
> basis of what is stored in later [association] areas. At least this
> model is easy to conceptualize [and to potentially model], if not
> wholy accurate biologically.
I say this is basic. Is the distinction between lion and cat a
question of molecular biology or is it not? You pays your money and
you takes your choice.
In my humble opinion, when Hubel and Wiesel first stumbled on the
truth that the cortical cell they had probed responded to a line
segment rather than a spot, a great divide in human thought occurred.
(Actually, that first cell was a complex cell that responded to a
moving line segment.) This was not shared by all. There is a letter in
which Marr referred to H&W's "silly little spots of light". Marr
wanted the cell to respond to a computation of the entire visual
scene, or at least a good portion of the scene.
I bridle at the word "stored". Synapses are altered, but nothing is
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