X-Message-Number: 26006
Date: Tue, 12 Apr 2005 07:54:25 -0400
From: Thomas Donaldson <>
Subject: To Yvan, re "uploading"

 To Yvan:  The chips you list for possible use in creating a brain still
remain far from what is needed. Moreover, if you make two copies of a brain
you'll have to make your circuitry automatically transfer changes in one copy
to the other, which will add to its complexity if nothing else (and brains
don't have that kind of complexity at all). Just what have you been reading
about how brains work, anyway?LTP and LTD are used by our neurons to make quick
changes inresponse to new impulses, but they aren't permanent. Theyhold those
changes while the neuron changes its connections andsometimes even grows a new
one for more permanent storage. Asyou can guess, it's this latter process which
is slow.As I've pointed out before, you do NOT want many neurons on onechip.
Your FPGAs don't look to me as if they could even imitateone neuron, anyway.
Your TRACs may be able to change 8connections (is that the small number they
have?) but lots of neuronsconnect to many more than 8 others. To be fair,
that's not true for ALLneurons, so the TRACs might sometimes fit.Yes, I admit
that some people (who I doubt have thought about thematter) believe that an
ACCURATE and WORKING version of a brainneed not have separate processors for
every neuron. They thinkso because Turing proved that a single computer could
achievejust as much as many working together. But if you bother to readwhat
Turing actually proved, he was talking about mathematicalcalculations rather
than acting in the world. And he thereforetotally ignored TIME. Even for
mathematical calculations thisstarts to look weak if we want to do a very large
calculation:sure, even the fastest processor can do the calculation alone,but
it will take 1000 years or more to do so. Whether we'reimmortal or not, I doubt
that anyone will want to wait 1000years for an answer to their calculation.
That's why parallelcomputers have grown so important. Briefly, TIME is an
importantvariable that Turing ignored.I honestly don't know just what books
would be best for you toread if you want to learn what we know now about how
brainswork. I would suggest THE NEURON, by IB Levitan and LK Kaczmarek;the
most recent edition of Shephard, NEUROBIOLOGY; and FROMMOLECULES TO NETWORKS
edited by JH Byrne and JL Roberts. Youmay also want to consult a book on
biochemistry (I had to doso when I first got into this subject, and I was also
helped bymy then wife, Catherine Woof, who actually studied biochemistry).I
myself actually believe that we'll someday be able to make brains. The
materials we'll use remain unknown, but the neuronswe make will still have to
have particular characteristics whichdon't look to me like anything our present
computer chips andparts can provide.            Best wishes and long long

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