X-Message-Number: 13729
Date: Mon, 15 May 2000 07:35:59 -0400
From: Thomas Donaldson <>
Subject: CryoNet #13724 - #13725

To Yvan:

The problem, as I said before, is not with computing power but with
understanding of how brains work. Yes, this includes how individual
neurons work --- since those in our brain do little unless they work
together. This means that ANYONE who wants to produce a working brain,
even as an ACCURATE simulation in a computer, must first understand
how brains and neurons work in the first place.

You aren't saved from this problem by going back and simulating the
activity of every neuron (not to mention that neurons aren't the
only important cells in our brains). As a simple illustration, I
just received the 24 March issue of SCIENCE (it arrived late, and I
asked for it because it was missing). On p.2262 there is an article
describing how AMPA receptors are brought to synapses after LTP. 
That is the status of our understanding of brain working in general:
we have a global idea but lots of details still need to be filled in.
And in terms of how neurons work, and hence how our brain works, 
those details are important. (It is the increase in AMPA receptors
at a synapse which causes LTP to last longer than the result of 
a few single impulses. LTP itself is begun with the activation of 
NMDA receptors, a different kind of receptor --- both kinds in real
life are activated by glutamate, but they can be distinguished by
the other chemicals to which they respond).

			Best and long long life to all,

				Thomas Donaldson

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