X-Message-Number: 7840
From:  (Thomas Donaldson)
Subject: Re: CryoNet #7828 - #7833
Date: Wed, 12 Mar 1997 11:27:59 -0800 (PST)

Hi!

I do not believe 21st CM compares at all with Visser.

About replacement or uploading of brain structures: while it is quite true
that the whole idea of neural nets came from study of how our brains work,
the electronic ones do not attempt to imitate brains except in the very
broadest sense. Perhaps the name has become misleading. And certainly, there's
been a lot of advances based on the electronic variety of neural net:
most work on recognition of any kind depends on them. And I've read a fair
bit about them myself, in my persona as a computer person. Ideally, of course,
they should not just be imitated on a PC, but made into fully parallel 
computers. Some companies have neural net boards which do exactly that.
(I've been interested in parallel computing particularly). 

My problem with Graham Clark's statement that electronic replacement will 
become available relatively soon comes simply from the fact that these neural
nets fail to imitate the actual behavior of brains or nets of neurons --- not
just in a minor way, but in major ways. Perhaps we WILL have some kind of 
replacement for some brain structures --- but it will be a replacement in the
same sense as a wooden peg leg is a replacement for a lost leg. Sure, you
can hobble around on it, but no one would be mad enough to claim it was a 
perfect replacement. In terms of what I would want to be uploaded into, the
last thing I would want would be to be uploaded into such a clumsy device ---
it would probably imitate me in the same sense as the peg leg imitates
a real leg.

The really major difference --- one which dwarfs the others --- is that 
nets of neurons involve GROWTH. Not so much growth of new neurons as growth
of new or modified connections. Again, to some extent that can be imitated
on a computer --- but with billions of neurons and lots of memories and 
experiences, that looks like a losing proposition. Do I believe that someday
we will be able to make neural nets which fully emulate nets of neurons?
Certainly. But it is a far harder problem than many on Cryonet seem to 
believe. And of course I haven't discussed all the lesser differences:
response to a wide variety of chemical transmitters, gap junctions between
neurons, and on and on.

			Long long life,

				Thomas Donaldson


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