From newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.ecf!utgpu!cs.utexas.edu!wupost!csus.edu!netcomsv!mork!nagle Tue May 12 15:50:06 EDT 1992
Article 5524 of comp.ai.philosophy:
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>From: nagle@netcom.com (John Nagle)
Subject: Re: what we know about neurons
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Date: Sun, 10 May 92 02:04:32 GMT
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References: <1992Apr9.174840.3407@organpipe.uug.arizona.edu> <5674@mtecv2.mty.itesm.mx> <2@tdatirv.UUCP> <1992May5.125445.22000@hobbes.kzoo.edu> <17@tdatirv.UUCP> <1992May8.051322.28285@organpipe.uug.arizona.edu>
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      Braitenberg has written a useful book titled "Anatomy of the Cortex".
(Yes, this is the Braitenberg of "Vehicles".  "Vehicles" is a flight
of fancy; "Anatomy of the Cortrex" represents years of electron
microscopy.)  The state of the art is disappointing.  Most of the
available data is gathered by slicing dead mouse brains into thin slices
and using an electron microscope to look at the result.  The slices are much
thicker than the level of detail in the brain, so the information is
high-resolution in two dimensions but low-resolution in the third.

       Not much is actually known.  The number of neurons in a mouse 
cortex is known to one significant digit.  It's not known where information
is stored.  It's not known if the connections change over time to store
information.  The connectivity statistics are known, but detailed
wiring topology is not.  Braitenberg makes some guesses about architecture,
but they're guesses, not solid facts.  It's worth reading his book,
though, because one can definitely eliminate some hypothesized 
architectures as being inconsistent with the data.

       The dissection technique to date is still too crude for the task
of reverse-engineering a brain.  

						John Nagle


