From: Rafal Smigrodzki (rafal@smigrodzki.org)
Date: Mon Jul 07 2003 - 18:48:07 MDT
Eliezer wrote:
>
> One problem I have, though, is that it still looks to me like it
> would be better to just chop off the head and drop it into a bucket
> of liquid nitrogen as fast as possible.
### Probably a bad idea. The freezing damage (microstructural) is extensive,
maybe reversible with some as yet not-invented technique, but quite possibly
too severe after all. Vitrification, and the, recently proposed by Alcor,
intermediate temerature storage at just below the glass transition phase,
should greatly reduce the damage, even including the gross fractures.
-------------------------------------
>
> I worry that cryonics has been approached from the viewpoint of
> medicine rather than information theory. Here is a point where lack
> of optimism about post-Singularity capabilities may have killed
> people - cryonicists thinking "let's keep the neurons as undamaged as
> possible from the viewpoint of biological function" rather than
> "let's try and create a physical freezing process such that the
> configuration space of pre-frozen brains is mapped to the
> configuration space of molecularly analyzed frozen brains in a way
> that does not introduce information-loss on the level of relevant
> functional information". These are not at all the same thing; one is
> concerned not with how much "damage" the freezing process does, from
> the viewpoint of ice crystal formation and so on, but rather with the
> question of whether ice crystal formation of just dumping a head into
> liquid nitrogen is a physical process that maps many initial states
> into one final molecular-level state to a greater degree than the
> retraction of axons and dendrites that occurs if you leave the brain
> without oxygen.
### You are correct to look at the problem from the information theory point
of view, but the specific application of your reasoning is IMO
inappropriate - freezing does much more damage in terms of information loss
(just a guess, prompted by looking at fresh-frozen brain sections) than a
perfusion and vitrification process, even if they take longer to complete. I
don't think it is reasonable to expect that vitrified neurons will ever be
brought back to life in some direct (biological) way, the only likely way is
through the extraction of functional information from them to guide
reconstruction in silico or in another biological substrate, as you
described below, and vitrification is likely to preserve this information
much better than anything else (except maybe fixation by perfusion).
--------------------------------------
>
> If dendrites and axons retract into the cell body within half an hour
> after the neuron has been starved of oxygen (!!!),
### This is not true.
Rafal
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