X-Message-Number: 4457
From:  (Thomas Donaldson)
Subject: re.#4449-#4453
Date: Fri, 26 May 1995 14:54:26 -0700 (PDT)

Hi everyone!

Re: brain repair

Brian, you should know that a lot of working is going on right now towards 
finding ways to regrow connections severed by strokes or injury, either in the
brain or in the spinal cord. Some brain regions will be quite amenable to this
even in frozen patients, since areas such as the hippocampus play a critical
role in learning but NOT in really long term memory (yes, someone repaired in
this way may lose several weeks of memory. But they woould still be the same
person, and alive: not to mention that such loses of memory from accidents etc
aren't uncommon even now). We do want to preserve connections in our cortex,
which probably holds our long term memory, and for which simple regrowth might
not be enough (we would want the same connections because they are very likely
to store our memories, not just "similar" connections).

I've mentioned this issue before, and at once time it was a big one in cryonics.
The barrier to brain and spinal cord repair occurs not because the ability to 
repair lost connections has been totally lost, but because in adult mammals
(though not in salamanders or frogs, for instance) other biochemicals are 
blocking that ability. Stop those chemicals from acting and the neurons will
start to regrow. We are getting close to the ability to repair severed spinal
cords. Brains will take a bit longer. 

The point of this is: even cracks might be repaired by processes close to the
natural ones. No advanced nanotechnology would be required. I will say, though,
that recovering lost connections in the cortex might well require much more
advanced repair technology, with some AI involved. But even large cracks (not
small ones) could be repaired by quasi-normal processes: that would be because
more than one cell or connection would be involved in our memories, so that
there would be some (as yet unquantifiable) acceptable loss. Widespread small
cracks would be quite another thing.

The next issue of my newsletter, PERIASTRON, will discuss work that has been
done in that direction, among other things. 

			Long long life,

				Thomas Donaldson

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