From: hal@finney.org
Date: Mon Feb 21 2000 - 23:45:32 MST
Billy Brown, <bbrown@transcient.com>, writes:
> Ischemic injury, AFAIK, is a very complex but highly ordered cascade of
> chemical reactions. It seems perfectly plausible that you could simulate
> the process in reverse to figure out what the original tissue looked like.
> The same is true of freezing damage. Using cryptographic analysis is just a
> different way of performing the same computation, like using a neural net
> instead of a procedural algorithm.
I think the problem with the cryptographic analogy is that cryptographic
transformations are, by design, reversible. All the information in
the plaintext is intentionally preserved, in scrambled form, in the
ciphertext.
However, chemical reactions are biased in the direction of increasing
entropy. The body's metabolic reactions have to constantly fight
this trend in order to maintain order. Once there is injury or death,
the forces of entropy will come into play. Increase of entropy means
loss of information. So I think it is likely that most injuries,
including trauma, ischemic and freezing injury, will involve some loss
of information.
The unanswered question is whether this information loss is sufficient
to obliterate personality, memory, and other important brain state.
I don't think we know enough at this time to give any sort of definitive
answer to this question.
This was my objection to the Ralph Merkle essay mentioned a couple of
weeks ago; I thought he was excessively optimistic in claiming that the
answer was largely known. But other people who have actually looked at
frozen brains, including Eugene and cryonics "godfather" Mike Darwin,
seem to have a more pessimistic view.
Hal
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