X-Message-Number: 5219
From:  (Thomas Donaldson)
Subject: Re: CryoNet #5182 - #5190
Date: Sun, 19 Nov 1995 10:15:02 -0800 (PST)

Hi again!

A brief point about brain transplants. They are being tried now for 
Parkinson's disease, and there have been some work on using them for memory 
loss also (not to replace the memory, but to replace some of the brain 
circuits which do the remembering).

The trick is to use embryonic brain tissue ---- although I would also comment
that if we knew how to flip the development switches that make the difference
between embryonic brain tissue and adult we would then know how to use 
adult tissue (and neuroscientists also work on that issue, too).

In some cases the implant helps simply because it is there to produce the 
right level of acetylcholine. (Inside our brains acetylcholine seems to act
not as a transmitter but simply as a stimulant). In other cases, actual
connections are needed. In such cases, the transplanted tissue will often
grow directly to the right spot (if it comes from a similar place in the 
embryonic brain). This work, among other interesting results, also tells us
that work on brain development (and not just on how memory works) may also
turn out to be important for cryonics. In some cases, we won't have to 
work out how to reconnect: it will be there in the development program of
the neurons. It's only our relatively primitive level of understanding about
how brains and bodies grow that make such questions seem to be problems which
must be solved by direct force (which incidentally, in brain repair, has been
tried many times without success).

			Best and long long life,

				Thomas Donaldson

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