X-Message-Number: 24065
Date: Fri, 07 May 2004 21:52:26 -0700
From: Mike Perry <>
Subject: Re: Computers and brains

[Thomas Donaldson, #24057:]

>However it still seems clear to me that we will not get a count of
>connections that grows like a polynomial as the number of neurons
>increases. It will grow much faster. So I'm not retracting the basic
>point of my previous message: growing new connections will turn out
>to be vastly more efficient than any system which contains all
>possible connections and turns them on or off as change and learning
>occur.

I'm not sure what you are referring to here, since the total number of 
"possible connections," one-way, involving N nodes ("neurons") is just 
N*(N-1), quite polynomial in N. The number of possible paths involving all 
N nodes occurring once is, as usual, N-factorial, which is more than 
polynomial. Will "growing new connections turn out to be vastly more 
efficient than any system which contains all possible connections and turns 
them on or off"? Another example that suggests to me the answer is no is 
the Internet, which offers the possibility of having arbitrary paths of 
connectivity involving the billions of humans on the earth. If we assume 
any human has a computer hookup, then you just need the email address of 
someone else to have a "connection" with that person. Much cheaper and 
faster than laying a special telephone line to that person.

Mike Perry

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