X-Message-Number: 12176
From: Thomas Donaldson <>
Subject: To Doug Skrecky: comments on dispensable brain areas, and others
Date: Fri, 23 Jul 1999 22:36:18 +1000 (EST)

To Doug Skrecky:

The scientific standard of your postings has gone up a good deal since you
first started several years ago. I've found several of your postings
quite useful.

However your message suggested something about how a brain is usually
preserved, something quite false. Because the vascular system for a brain
comes in from the outside, if we try to remove it from the skull we're
risking lots of damage to the very system we'd use to perfuse
cryoprotectant. The only cases in which brains have been preserved for
cryonics while not preserving the head have been cases in which the brain
was already damaged so much that it could not even be perfused with
cryoprotectants in the first place. TransTime, for instance, did that
with the brain of a 15 year-old murder victim.

As to whether it makes a difference whether or not you choose to be
preserved as a head alone, or as a whole body, I'd say the jury is still
out on that one. My personal opinion is that if we can revive a head
cryopreserved with CURRENT methods, then we'll be able to make it grow
a new body too (the first is much harder than the second). That situation
may not continue if the work on improved methods of cryopreservation in
cryonics proceeds... at least for those fortunate enough to be able to
use such work (the fate of the murder victim would not be affected by
advances in cryopreservation, and other less spectacular misfortunes
can also happen ... cryonics is emergency medicine, after all). I actually
hope that it does not continue, if only because it would be very good
to know that our brain would remain intact and revivable.

One other issue about preservation of a complete brain: it is one thing
to grow up with half a brain, and quite another to have half your brain
removed when you are an adult. That latter case will cause damage, 
depending on just which hemisphere is lacking. Yes, the missing hemisphere
might be added, complete with connections, but somehow even then there
remains the issue of just what parts of personal memories may have been
lost. At the same time, if we look closely at the function of different
areas in our brain, it's quite clear that some areas, particularly
lower areas such as the amygdala, might well be recreated afterwards
with no loss at all. (I"m not saying that our amygdala isn't important,
just that it may depend much more on our genes rather than our experience,
and therefore be easily recreated).

A full understanding of how brains work is likely to show up many
brain areas which we hold in common and which therefore need not be 
preserved to preserve a person. The major nerve tracts in our brain
provide a second example: though it's unlikely that they could be 
removed, their repair might only require copying a standard pattern...
or at most, a pattern gotten from the genes of the patient. Again, some
areas which even I would have once thought were dispensable (in this
special sense: easy to replace, NOT dispensable in a person awake and
living in the world) such as the cerebellum turn out to contain memories,
too. And there's some chance that even our hippocampus, which seems mostly 
to act as a "door" for letting memories in and reading them out, may hold 
its own special memories.

			Best wishes and long long life,

				Thomas Donaldson

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