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From: smoliar@vaxa.isi.edu (Stephen Smoliar)
Newsgroups: comp.ai
Subject: Re: How much info can the brain hold?
Summary: Is this a well-formed question?
Message-ID: <15882@venera.isi.edu>
Date: 2 Dec 90 21:24:41 GMT
References: <11941@hubcap.clemson.edu> <7492@hub.ucsb.edu> <33870@netnews.upenn.edu>
Sender: news@isi.edu
Reply-To: smoliar@vaxa.isi.edu (Stephen Smoliar)
Organization: USC-Information Sciences Institute
Lines: 51

In article <33870@netnews.upenn.edu> sklarew@eniac.seas.upenn.edu (Dann
Sklarew) writes:
>
>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."

I would like to contest the assumption behind this calculation.  Actually, what
I want to contest is the validity of using a phrase like "sites of information
storage."  Therefore, I shall see your Sejnowski quote and raise you one
Edelman quote.  This comes from the exposition of his theory of memory as
a process of REcategorization (a theory recently explained quite lucidly
by Oliver Sacks in the November 22 issue of THE NEW YORK REVIEW in an article
entitled "Neurology and the Soul").  Here is Edelman talking about
recategorization on page 266 of his book, NEURAL DARWINISM:

	Inasmuch as the recategorization carried out by classification
	couples has a variable element and because categorization is a
	continually ACTIVE selective process of disjunctive partitioning
	of a world that exists "without labels," the static idea of
	information as it is used in communication theory is not very
	appropriate.  It is true that, as the amount of categorization
	of members of a set increases, there is an accrual of adaptive
	behavior and of response generalization;  it is also likely that
	this is accompanied by a decrease in degeneracy [redundancy] in
	the neural circuits mediating the response.  But inasmuch as
	there is always a trade-off between specificity and range in
	selective systems (see chapter 2), and because there is, in
	general, no prior prefixed or coded relation between an animal's
	behavior and objects and events in its present environment, it
	is not illuminating to talk of information (except A POSTERIORI,
	as an observer).  It is equally fruitless to attempt to measure
	the capacity of such a system in information theoretical terms:
	reaching a response that even vaguely categorizes a stimulus by
	trading some specificity for range puts an animal in a reasonably
	good position for adaptive behavior.  If that behavior is rewarded,
	the gain or loss in the amount of "information" is an EX POST FACTO
	judgment the efficacy of which is dubious.

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