From: Yan King Yin (y.k.y@lycos.com)
Date: Mon Jan 31 2005 - 16:52:32 MST
Phil G.:
>[...]
> I shouldn't have stated this so confidently when
> it relies on my personal, not-universally-accepted
> notions of how the brain works.
I haven't posted to this list for a while, but your post
sounds interesting and is very similar to what I'm
thinking...
> If you imagine that the brain processes stimuli,
> and converts them into something like symbols,
> and then manipulates these symbols somewhere (say
> prefrontal cortex) to,
> say, come up with a plan, and then pushes the
> resulting plan symbols back towards the brain's
> posterior (towards motor cortex) to carry out the
> plan, then what I said wouldn't follow.
>
> I do think that the brain does something like
> symbol-processing, because we can productively
> generate an infinite number of, for instance,
> sentences fitting a language's grammar.
> But I don't think these symbols are cut off
> from the sense data that gives rise to them.
> If this were so, non-verbal priming would not have
> such dramatic effects on abstract thought. Also,
> concepts would probably be more neatly defined,
> along the lines of necessary and sufficient
> conditions; or at least, we would have difficulty
> working with non-typical category members, working
> with metaphors, etc. IMHO.
>
> I think that whenever a "symbol" is active somewhere
> in anterior cortex, it is linked to, and activates (or
> is activated by), a series of cortical areas
> connecting it all the way back to the posterior
> sensory cortex. There's some evidence for this;
> primarily I'm thinking of experiments that show
> that visualization activates primary visual cortex.
> Damasio's work on "convergence zones" is an example
> of a theory of this type. Also any theory that
> involves using different frequencies to create
> different "bindings" between cortical areas.
>
> Say you're using neural darwinism in cortex area A to
> select between different planned movement sequences.
> If you buy into my notion of how the brain works,
> that means that each competing program in area A has
> to be activating all of the other cortical areas
> that create/correlate with the "symbols" being used
> in area A. All the way back into sensory cortex,
> or at least premotor cortex. And to prevent
> collisions, that means that EVERY SINGLE CONCEPT
> stored in every cortical area needs to be stored
> hundreds of times over, so that these hundreds of
> copies can be activated separately and used
> simultaneously by competing programs in your planning
> cortex.
> [...]
IMO the neural evolutionary process can be distributed
among individual neurons or even synapses. This is the
"internal evolution" paradigm that I recently proposed.
In other words, it doesn't have to be among large
populations of neurons.
Personally I'm quite confident that this is how natural
nervous systems had evolved over evolutionary time. But
I'm not so sure whether a similar evolutionary mechanism
is responsible for "thought processes" in the brain in
real time. This would be a very interesting topic...
YKY
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