From: Robert J. Bradbury (bradbury@aeiveos.wa.com)
Date: Sun Feb 06 2000 - 14:58:26 MST
On Sun, 6 Feb 2000, Eliezer S. Yudkowsky wrote:
> Forget the problem of repairing the brain. Think of it in uploading
> terms.
Well Eliezer, not everyone may want to be reanimated as an upload.
Some of us might want to putter around the galaxy in our interstellar
star-hopper until we make some fatal mistake in navigation or alien
diplomacy. Its so much more romantic that way compared with dying
a thousand deaths in an SI VR.
> The theoretical question is: "If you know where every single
> atom in a frozen brain lies, could you extract an model of the brain's
> operation with such high resolution that the informational damage caused
> by freezing would not be significant (on a damage scale calibrated by
> the effects of neural death and quantum/thermal randomness in day-to-day
> operation)?"
This is pretty much the question I'm trying to get at. Hal responded
to some degree expressing his doubts. From my perspective, the
questions are:
(a) Does the process of ice crystal formation develop enough force
to break interatomic bonds or will the crystals almost universally
disrupt H-bonds and Van der Waals interactions?
(b) What is the probability that within a some fixed (sub-cellular) volume
that I will have identical surfaces that preclude putting things back
together exactly the way they were originally?
With regard to (b), I find it hard to believe using nanodis-assemblers
that I could not remove all of the ice *entirely* (e.g. creating
approximately a freeze-dryed brain), then map all of the surfaces
and not discover *exactly* where the various synapses should be
positioned and setup the required repair operations. I'd envision
you would have nanobots carefully positioned around the broken
pieces, preprogrammed to slowly heat the tissue and execute vector
movements designed to properly reposition things. Only if the damage
includes the breaking of covalent bonds [e.g. (a)] does the process of
repair become more difficult (having to replace broken chromosomes,
proteins, etc.).
> I think this sounds reasonable; damage to structure on the
> >10^6-atom-scale may appear to destroy the information contained on that
> level of abstraction, but the same information should still be
> obtainable from the internal structure of the mostly-untouched inner
> volumes of the 10^6-atom units being shoved around. If so, then the
> practical question is extracting the information without causing exactly
> the sort of atomic-scale disruption that would destroy that level of
> abstraction as well.
Since we seem to be able to do this level of "atomic" surface sensing
(molecular fingerprint recognition using AFMs) and you have things like
laser driven decomposition of surface layers (currently used for things
like DNA sequencing via mass-spec), this seems highly feasible to me.
Furthermore, taking apart a small number of cells will give you the
genetic blueprint (and consequently the 3D blueprint) of all of the
molecules (excepting perhaps viruses or nutrients) that should be
in the cells. I see this as no different from paleontology where
you can recognize a dinosaur from a fragment of bone sticking out
of a rock formation. My sense of the molecular biology of the brain
at this point is that you could probably destroy the contents of
every single cell so long as you did a highly accurate inventory.
Then once you get all of the cell membranes and synapses in place, you
fill the cell with water, repopulate the molecular contents and
off you go.
The contents of the cell is probably highly flexible as well.
I would guess that as long as you get things "balanced" sufficiently
that the cells will "run", you will be ok. The only places where
the contents is important are when you are dealing with internal
messangers involved in increasing synaptic strengths. Since you
"died" anyway, it will probably be like coming out of a coma
or a very deep sleep, so I suspect any disruption of short term
memory formation, because you don't get the molecule counts
completely correct, is going to be unimportant. You might end
up being a different person than you would have been had you
not undergone the suspension and reanimation but it begs the
question of whether or not some of us end up as different persons
because we experience high or low blood sugar once or twice a day.
Robert
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