Re: Cryonics: A question

Carl Feynman (
Wed, 25 Jun 1997 10:42:08 -0400

At 03:06 AM 6/24/97 -0700, James Rogers wrote:
>How does cryonics preserve the information in the brain?
>It appears to me that given the amount of time required to get the body to
>an appreciably low temperature, it would allow the chemical/ionic
>potentials in the brain to approach something resembling equilibrium.
>Since the brain structure is merely the hardware, wouldn't a brain in
>equilibrium essentially be a blank slate?

Chemical potentials in your brain only store information for a few seconds
or minutes ("short-term memory"). Information that lasts longer than this
is stored as permanent microstructural changes, and will be preserved by
freezing. Head injuries, electroshock and deep anaesthesia all wipe out the
chemical potentials, and the result is that you lose a short while of memory
from before the insult. But destruction of short-term memory certainly
doesn't disrupt your personality.

>Also, on a more technical side, is liquid Nitrogen capable of stopping
>ion/molecular transport, or just slowing it down? If there was small but
>finite transport activity, it would put a "shelf-life" on information
>stored in a cryo-brain.

The rates of chemical activity are too small to measure at that temperature,
but theory and experiment agree that the rates drop exponentially with
temperature, so we can measure the rates at higher temperatures and
extrapolate. The result is a shelf-life of centuries.