X-Message-Number: 10262
Date: Mon, 17 Aug 1998 10:21:03 -0700
From: "Joseph J. Strout" <>
Subject: emulation by "computers"

In Cryonet Message #10250, Thomas Donaldson <> writes:

>There is a strong connection with cryonics, if you listen a bit. You
>see, there is one segment of opinion among cryonicists that we might
>eventually be emulated by a computer. Computers work by means of
>manipulating symbols (if we exclude neural nets, which some may not
>even see as computers). If ALL thinking consists of such manipulation,
>then the claim of such cryonicists is proven. If it does not, then
>the possibility that we cannot be emulated by any computer at least
>becomes relevant and perhaps even important.

As more or less the de facto "voice" of mind uploading within cryonics, I
feel obliged to respond.  Thomas is laboring under a misconception here.
The idea of mind uploading is that the brain can be emulated by some
*artificial device*.  Such a device will almost certainly resemble what we
call a computer today no more than my PowerMac resembles a mechanical
hand-cranked calculator of the 1930s.  A brain emulator will, in all
likelyhood, consist of custom hardware, perhaps analog rather than digital.
(In the limit, it may consist of proteins and lipids, but I think this
rather unlikely.)

Neurons (or at least, their spike initiation zone) can be emulated today in
real time on conventional computers.  But this neglects all the complex
analog processing going on in the dendrites.  To imitate that
functionality, we generally use either compartmental models or Wiener
kernels, but when we do this in a digital computer, it requires
discretizing time and space.  The result is a simulation that's slow, or
inaccurate, or both.  But already there is a field of "neuromorphic
engineering" which is building analog VLSI hardware that mimics some of the
functionality of neurons (often by implementing a Wiener kernel model for
each neuron).  These devices are already proving useful in machine vision
etc., and they do nothing that resembles "manipulating symbols" any more
than our own retinas or brains do.

So it's a little misleading to speak of uploading as if it requires
emulation of the brain in digital, symbol-processing hardware.

>Why computers? Because at least to some they seem to provide a way to
>resurrect us even in the worst cases.

This is the idea, but please strike "computers" and insert "artificial
devices."  (And consider adding that such technology does not seem to
require nanotechnology, provides a means for making backups in case of
disaster, and would enable us to adapt ourselves to a much wider extreme of
environments than is plausible for biological materials.)

Best regards,
-- Joe

|    Joseph J. Strout           Department of Neuroscience, UCSD   |
|                 http://www.strout.net              |

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