X-Message-Number: 9172
From: Thomas Donaldson <>
Subject: Re: CryoNet #9168
Date: Tue, 17 Feb 1998 00:17:50 -0800 (PST)

Hi again!

Some additional points: you suggest that we can read off memories from the
frozen structure. Unfortunately, if that structure is broken and distorted,
as it probably is from current suspension methods, your readout will also
be just as broken and distorted. So it is not nearly so simple as you say.
Not only that, but brains are 3-dimensional and micrographs are 2 dimensional,
so you must have many micrographs to have any hope at all of reconstruction.
Moreover, you will almost certainly have to know a good deal about how 
brains normally connect: given that the one you're looking at ISN'T normal
but damaged, just how are you proposing to reconnect it without such 
knowledge? And I am saying that if you have that knowledge you will be 
close to knowing how to reproduce those connections in a biological system.

I will discuss that a bit more, right here. The kind of knowledge you will 
need is that of such things as the processes by which neurons create new
synapses, and the neurons which are likely to acquire those new synapses. 
For instance, one theory posits that pyramidal neurons do not change their
axons, but the change in learning comes by changes in inhibitory neurons
using GABA (this is presently a hypothesis, as yet unproven, but it tells
us something about what might connect with what else). There are several
different kinds of neurons which connect to our pyramidal neurons and use
GABA as their transmitter. Moreover both axons and dendrites seem to be 
changeable: they move about a bit, presumably as some connections form and
others disappear. You would need to understand how that happens, in detail:
both the growth and the loss of synaptic connections. For any repair,
we will need first to work out just what connects with what (currently
a problem --- remember we need to do that not on a gross scale but on the
very fine microscopic scale on which our neurons form memories) and then
if something has happened to that connection, get it to regrow. If we
revive the neurons it should not be difficult to use systems developed
from lymphocytes, bacteria, and other such semi-independent creatures to
put the proper trophic substances in the proper places. For what it's worth,
a 2-dimensional micrograph doesn't come near to telling us about the 
damage due to freezing: so long as we could find membranes (though pierced
and damaged) connecting one part of a neuron with another, then the 
problem becomes not that of forming connections between neurons but of
repairing a single neuron. If and when that happens, it makes the problem
much easier: no need to work out connections which no longer exist by
inference from what you find in the damaged system. 

And however you examine your brains, frozen or not, you will have to examine
them on that scale AND in 3 dimensions. Not only that, but your examination, to
be at all thorough, must involve not just the APPEARANCE of the damage but
also its CHEMISTRY. We work not just electrically but also chemically, and a
knowledge of just how that chemistry works will be important in any attempt
to find out the original structure of a damaged brain. You say that you do 
not like nanorobots, yet how do you propose to make your pictures of damaged
brain structure at the required resolution without such devices? If you can
work at that scale, you are very close to being able to repair at that scale. 
And for that it won't really matter what materials your repair machines (or 
(or highly modified systems of lymphocytes and bacteria, or whatever)
consist of: a nanorobot of nonorganic materials can just as well spread around 
a trophic molecule as directly connect two parts of a severed dendrite.

Of course, if the current plans to be able to freeze undamaged brains work
out, then no such readout is needed, nor will we need any uploading at all.
We merely revive the brain --- from vitrification or whatever.

Finally, existing neural nets in computerdom do NOT match those of brains. 
Sure, just as in many other things we can obtain machines which in some
ways come close. But the growth of new connections is essential to the way
we learn; no neural net to which I am acquainted does that. If you go off
and build one that does, then what I say will cease to be true. It's not
enough just to imitate SOME pertinent features of neurons. To make a brain
you will need to imitate all of them. Spiking, as you probably know, is
likely to play an important role encoding our thoughts, and in that
respect I'm not surprized that we can make electronic models behaving the
same way. But we don't just think with our brains. We also learn with 
them. And we feel with them too. 

Finally, I will make some other points to explain just what I think about
these issues. First of all, my problem with uploading of any kind comes
from my desire not to be uploaded into a computer (though someday I might
be STORED in a computer, inactive). I do not believe that computers can act 
as brains. I do not claim that this means that we could not build a 
brain of very different materials. I even think it LIKELY that we can do
that. But if I understand you, you seem to believe that doing so will
somehow be NECESSARY. Given that the strongest version of nanotechnology
right now is BIOtechnology, I doubt that very much, even for low temperatures.
(Right now there is intensive work on getting biochemistry to work in 
solvents other than water -- like glycerol, for instance. And actually 
applied industrial work doing this already exists). For that matter,
if we really want to be revived, we want not just a brain but all the rest,
which adds to the difficulty if you want it to consist of nonbiological
materials. You set yourself a very hard problem there, not just to create
a totally new form of life but to create instances of it which are close 
to YOU. And I assume that you too want not just to be able to think but
to learn and feel.

So over to you, now. 

			And best wishes, and long long life,

				Thomas Donaldson

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