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From: mwd@cray.com (Mark Dalton)
Subject: Re: Thought Question
Message-ID: <1995Jan3.004840.9828@walter.cray.com>
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Date: 3 Jan 95 00:48:40 CST
Xref: glinda.oz.cs.cmu.edu comp.ai:26189 comp.ai.alife:1614 comp.ai.philosophy:24246

David Fried (dfried@lynx.dac.neu.edu) wrote:
:  While I would agree that the human brain could not be simulated using
: current *hardware*, that does not mean that the brain could not be
: simulated by a computer.  You argue that while the human brain is
: constantly changing its phisical form (adding synapses, strengthening
: and weakening connections, etc.) its hardware - the complex organic
: chemicals that make up the functional parts of neurons - is relatively
: static.  The brain does not change the structure or use of these
: chemicals, it simply moves them around.

I agree that it can be simulated.  But there is a difference in a simulation
and reality.  It can already give us insight.  But I think the question
was why cann't we call a computer a brain (or something like that).
There are actual changes in physical conformations of the cells, proteins,
etc.  Changes of concentrations.  The point is that a change in the stereo
chemistry of a molecule can GREATLY affect it usage, effectiveness, etc.
it could be considered the difference between a 0 and a 1 in computer science.

:   Therefore, a human brain might be simulated by a computer designed 
: to mimic the underlying chemical structure of the brain.  This computer 
: would control a network of "neurons" and "synapses" created entirely
: within its own memory banks.  This network could then be modified "on
: the fly" as the computer runs.

I agree, a computer can simulate a brain.  The point is that it will still
not be a brain.

:   Unfortunately, this approach requires that we understand the inner
: workings of the brain, which we clearly do not.  It also requires that
: we are able to build a computer with the specifications listed above,
: which we cannot.  It does seem that at least at present, is it
: impossible to simulate the human brain.

Correct, they are still not understood.  There has been some work on simulating
the brain via Neural Nets - Joseph Sirosh, and Adaptive Simulated Annealing
by Lester Ingber.  A simulation is used to give insight, and we can do that
to a limited degree.

Thanks!

Mark
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Mark Dalton       CH3-S-CH2 H H                    H      O       H
Cray Research,Inc.      |   | |                    |       \      |
Los Alamos,NM 87544     CH2-C-COO    //\ ---C--CH2-C-COO    C-CH2-C-COO
mwd@cray.com                | |     |  ||   ||     |       //     |
                            H NH2    \\/ \ / CH    NH3    O       NH3
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URL = http://lenti.med.umn.edu/~mwd/mwd.html

