From: Jim Hart (jqhart@hotmail.com)
Date: Mon Feb 28 2000 - 12:46:48 MST
Thus sprach Eugene Leitl:
>His description of the state of the neural tissue due to
>ischaemia/freezing is entirely incorrect. I hate to be blunt, but he's
>moving entirely outside of his area of expertise.
It's very unfortunate that the computer scientist Merkle knows
little about neural tissue damage, while cryobiologists like
Fahy and Darwin know next to nothing about computational
techniques which are available to recover corrupted structures
which seem, to one untrained in such techniques, to be
utterly unrecoverable. Thus, alas, there exist *no* expert
opinions on the chances of future repair of the damage
sustained in cryonics.
"What we have here is a failure to communicate".
>(assuming a
>nondissipative, deterministic physical process despite dramatic
>evidence to the contrary
Freezing is largely nondissipative. Cracked and displaced
surfaces, furthermore, leave around a large amount of information
on matching surfaces, like a jigsaw puzzle. Thus for freezing
damage Merkle's analysis may be too *pessimistic*: we can often use
pattern matching rather than the computationally more expensive
cryptanalysis/machine learing techniques. Ischemic damage
is another matter. It involves quite dissipative chemical
reactions. There is good reason to believe that freezing
damaging will be vastly easier to correct than ischemic damage.
The good news is that hypothermic conditions, for example
hypothermic surgery, have been observed to prevent ischemia
for hours at a time. Unfortuneately good hypothermic
conditions are often absent. Prevention of ischemic damage
needs much further study and higher priority in cryonics procedures.
Another piece of good news (for cryonics!) is that ischemic damage
is a very common event, for example stroke, that the brain
has to some extent evolved to protect against, for example
through redundant storage of long term memories. Brain
damage from stroke is usually the result of loss of function
of parts of the brain the function of which is to retrieve
and process long term memories, rather than loss of the long
term memories themselves. So after even a major stroke
lasting for days the information is usually still there.
These are all testable claims and it would be great to
discuss studies on hypothermia, stroke, etc. rather than
continue to speculate. There also needs to be more
cross-disciplinary learning between computer scientists and
cryobiologists.
Jim Hart
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