X-Message-Number: 15344
Date: Mon, 15 Jan 2001 07:39:41 -0500
From: Thomas Donaldson <>
Subject: new connections for neurons

Hi again!

A very brief answer to Mike Perry:
The basic theory currently behind how we store our memories would say
that we store them in the connections of our neurons. This means that
a given connection of neurons would contain a particular set of memories.
As I mentioned in my last discussion, this does mean that for a brief
time we could have an imitation of a human being with a particular
set of memories.

However those connections, at least those which are not determined 
early in life, will be changing constantly. New memories will be acquired
and some older memories will be forgotten or modified (consciously or
nonconsciously). This means that the imitation of a human being would
not last long at all before the real human being it imitates would
acquire very different sets of connections. Just how he or she does 
this does not matter here; the point is that the low figure he discusses
is for an instantaneous static picture. If we want to discuss all the
different memories such a person may have learned in the past or will
learn in the future, we're immediately plunged into factorials such
as N!. 

Forgetting for a moment the really important issue of TIME, the issue
here is whether or not a Turing machine could imitate such a machine.
Certainly it could imitate the instantaneous static picture, but real
persons (and real machines with brains behaving like our own) would
quickly differ from their static picture. To work out just what they
would come, we must look at all the possible connections they might
develop... and so find ourselves among factorials and exponentials.

Could the common theory now held by many neuroscientists break apart
and be replaced by another one? Well, yes. Ideally we'd want our memories
to consist of more than the connections between neurons. Such connections,
for a cryonicist, may be very unstable against freezing. In PERIASTRON
I discuss some possibilities, but they remain only possibilities.

Again, some neuroscientists believe not that we form or lose new/old
connections between our neurons but that the connections acquire 
some features they did not have before the learning. A little thought
suggests that such a theory will have its own exponentiality: we have
lots of connections but their "weight", say, changes constantly when
we acquire new memories. (One major problem with this theory is that
experiments have shown a constant formation and destruction of
synapses connecting neurons, but that is a long discussion in itself).

In any case, this is why I choose N! when I try to calculate the
behavior of a brain. In computer terms I am discussing the possible
states of a computer, while if we look only at its memory at one
time, we get a much smaller set of connections or weights for neurons.
That is not a possible state but only one of them, and as such tells
us very little about what the computer can do.

		Best wishes and long long life for all,

			Thomas Donaldson

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