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From: sklarew@eniac.seas.upenn.edu (Dann Sklarew)
Newsgroups: comp.ai
Subject: Re: How much info can the brain hold?
Message-ID: <33870@netnews.upenn.edu>
Date: 2 Dec 90 03:33:47 GMT
References: <11941@hubcap.clemson.edu> <7492@hub.ucsb.edu>
Sender: news@netnews.upenn.edu
Reply-To: sklarew@eniac.seas.upenn.edu (Dann Sklarew)
Organization: University of Pennsylvania
Lines: 41

In article <7492@hub.ucsb.edu> 6600dt@ucsbuxa.ucsb.edu (Dave Goggin) writes:
>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'd follow up with another questin of brain
>computer comparison.  It is known that much of the
>brain's power comes ffom the high degree of
>paraallel processing involved.  What is the speed
>(in MHz, or other units) that the brin runs at, and
>how does it vary with state.  Also, how does this
>compare witht existing parrallel-processed hardware?
> 

Computational neuroscientist Terrence J. Sejnowski (Salk Institute) has 
cited the best current estimate of brain complexity as 10exp14 
synapses: "If we assume that synapses are sites of information storage, 
then we can make a rough estimate for the total information stored in 
the brain (given that each synapse stores only a few bits). . . around 
10exp14 bits." Given an activation rate of 10 synapses per second, he 
states that the brain must be performing at least 10exp15 operations 
per second. This is a full five orders of magnitude above the capacity 
of the Connection Machine, one of the largest of today's highly paral-
lel computers. Thus, beyond the total number of neurons in the brain 
(10exp12 according to neurobiologist Eric Kandel), it is this intricate 
synaptic connectivity that allows the brain to out-perform advanced 
VLSI technologies.

Ref: 

Sejnowski, Terrence. 1989. In "The Computer and The Brain: Perspectives 
	on Human and Artificial Intelligence," edited by Jean R. Brink 
	and C. Roland Haden. New York: Elsevier.

Includes a figure of the logarithm number of elementary operations per 
second by the largest digital computers plotted as a function of time 
(a line estimated to reach aforementioned brain capability by 2020).


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