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From: syswerda@bbn.com (Gilbert Syswerda)
Newsgroups: comp.ai
Subject: Re: How much info can the brain hold?
Message-ID: <61534@bbn.BBN.COM>
Date: 12 Dec 90 18:56:52 GMT
References: <11941@hubcap.clemson.edu>
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In article <11941@hubcap.clemson.edu> svissag@hubcap.clemson.edu (Steve L Vissage II) writes:
>I've heard estimates of how many neurons the human brain contains, somewhere 
>in the trillions, I believe.  Has there ever been a reliable estimate of
>how much information, in bits or other computer-relevant units, can be
>contained in that structure?
> 
>I ask because, if we don't know exactly HOW we store information (we still
>don't know, do we?)  can we estimate how much?

Jacob Schwartz estimates the capacity of the human brain in an article in
the Winter 1988 Daedalus. It is an interesting article, with estimates
based on brain physiology. With regard to your questions:

  "...Such exceedingly rough quantitative guesses lead us to estimate that
the long-term memory available to the brain is about 10,000 trillion bytes
and that the amount of shorter-term data needed to characterize the state
of each of its synapses is roughly the same. The logical activity of each
neuron can then be regarded as a process that combines approximately 10
thousand input bytes with roughly 40 thousand synapse status bytes at a
rate of 100 times each second. The amount of analog arithmetic required for
this estimate is (again very roughly) 10 million elementary operations per
neuron per second, suggesting that the computing rate needed to emulate the
entire brain on a neuron-by-neuron basis may be as high as 1,000,000
trillion arithmetic operations per second. (Of course, computation rates
many orders of magnitude lower might suffice to represent the logical
content of the brain's activity if it could be discovered what this is.)
   It is interesting to compare these exceedingly coarse estimates with
corresponding figures for the largest supercomputer systems likely to be
developed over the next decade. These will probably not attain speeds in
excess of 1 trillion arithmetic operations per second, which is about
one-millionth of the computation rate that we have estimated for the
brain."