human vs machine

M. Ferber Ferber at zoology.uni-frankfurt.de
Tue Aug 8 02:13:50 EST 1995


tgmk at aol.com (TGMk) wrote:
>Any fool can see that with enough elements one could make a brain
>out of non-biological materials. But how many would you need?  That 
>is, how many neurons are in the (typical) human brain?  We have an old
>biology book that says *at least* 100 billion but I'll bet there are >more.
>And how many connections do they each have?  Of course, this is basic
>AI stuff but I'm too lazy to go to the library.  Pls send reply to 
>TGMK at aol.com.   Thanks! 

If this is true I must be really stupid. I'm working with the central 
nervous system of insects. They have really small brains (or ganglia) 
which contain from several hundred (abdominal and thoracic ganglia) to 
one or two million neurones (brain). It is even in such a simple system a 
hard thing to understand a simple behaviour like respiration or the 
regulation of joint angles. In these cases only few neurones, usually 
much less than a hundred control the behaviour.
The problem mentioned by tgmk (whoever he or she is) is not simply 
related to the number of neurones. The fact is that the connections 
between the elements of any nervous system are specific. Furthermore each 
element (neuron) within a nervous system is connected to many other 
neurones. There are no simple 1 to 1 connections. For the human brain an 
average of 1000 connections per neuron has been suggested. This togerther 
with the 10 exp 12 (1.000.000.000.000) neuornes makes 10 exp 15 
connections or synapses. Is it really possible to put such a number of 
elements together to a synthetic brain. I think it is not. 

Regards 
Micahel Ferber






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