Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!dcatla!dnhjm
From: dnhjm@dcatla.UUCP (Henry J. Matchen)
Newsgroups: comp.ai
Subject: Re: Building a brain
Keywords: hardware brain
Message-ID: <25687@dcatla.UUCP>
Date: 16 Oct 89 17:55:25 GMT
References: <14079@well.UUCP>
Reply-To: dnhjm@henry.UUCP (Henry J. Matchen)
Distribution: comp
Organization: DCA Inc., Alpharetta, GA
Lines: 44

In article <14079@well.UUCP> nagle@well.UUCP (John Nagle) writes:
>
>       So, to get the raw CPU power of a brain, we need about 5000 boards,
>or 227 standard VME cages, or 76 racks, or about 150 linear feet of cabinetry.
>
>       I've worked in mainframe installations bigger than that.
>
>       If we knew how to solve the architecture problems, we could build
>the hardware.  

But, the architecture *IS* the problem.  Consider the number of possible
number of interconnections between 5000 boards, then consider the number of
neural interconnections in the brain.  In the former, the architecture is
mostly linear (or parallel, if it's fairly sophisticated.)  The brain is
very nonlinear, with a single axial impulse generating dozens, then hundreds,
then thousands of response impulses.  The response domain depends on actual
(read hardware) connections, of course, but also on triggering and inhibiting
factors and threshold effects.  These factors are in turn determined by the
brain's environment-- the body's neurovascular subsystems-- as well as by
feedbacks which are both genetic and heuristic.

As a comparison, suppose you sometimes had to type the same command on your
terminal two or three times before that 150-foot Itty Bitty Mind in the next
room would listen to you.  Suppose that, after a while, the machine would
let you type one or two characters of a command, make a (not necessarily
correct) assumption about the remainder of the command and execute it.
Suppose that the responses, as well as the response time, changed when other
users were using the machine, as well as with the order of your commands.

The fascinating aspect is that the brain, for all its complexity, produces
a fairly small set of responses.  This elegantly deceptive simplicity
conned a lot of neural researchers into thinking they could isolate various
functions within the brain.  All they were seeing, or could see, were the
"I/O controllers"; the higher functions were part of the brain's "background
noise", so they missed them.  To make matters even more interesting, folks
applied what they knew of peripheral neural systems to the brain, and
ended up looking for hardwired stimulus-response patterns.  These exist, of
course, but they don't explain much.

A final comparison: lop about 50 feet off of that mainframe and you end up
with a slightly slower mainframe.  Scoop out one third of an average brain
and you end up with a politician ;^{).

Henry