From newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!rpi!think.com!mips!samsung!uunet!tdatirv!sarima Tue May 12 15:49:39 EDT 1992
Article 5478 of comp.ai.philosophy:
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>From: sarima@tdatirv.UUCP (Stanley Friesen)
Newsgroups: comp.ai.philosophy
Subject: Re: syntax and semantics
Message-ID: <17@tdatirv.UUCP>
Date: 7 May 92 22:01:02 GMT
References: <1992Apr9.174840.3407@organpipe.uug.arizona.edu> <5674@mtecv2.mty.itesm.mx> <2@tdatirv.UUCP> <1992May5.125445.22000@hobbes.kzoo.edu>
Reply-To: sarima@tdatirv.UUCP (Stanley Friesen)
Organization: Teradata Corp., Irvine
Lines: 33

In article <1992May5.125445.22000@hobbes.kzoo.edu> k044477@hobbes.kzoo.edu (Jamie R. McCarthy) writes:
|sarima@tdatirv.UUCP (Stanley Friesen) writes:
|
|I read once that, although we know a lot about single neurons, we are
|quite ignorant of how two neurons connect.  It was asserted that the
|Golgi stain method is our only means of viewing cells, and that it only
|affects, randomly, one cell in a thousand.  Thus, we've never seen two
|neurons next to each other, so we don't really know how they interact.
|
|Was this written before the electron microscope?  Please excuse my
|ignorance of biology...

Well, it is true that Golgi staining is the primary way of staining neurons
for optical viewing, but we have many other ways of studying neuronal
connectivity.  One major method involves retrograde degeneration - the axons
of a killed cell die off, so one can see which connections disappear, and
so estimate connectivity.

Also, you are quite right, the EM allows a gret deal more detail to be seen.
[Though this is mostly on a very small scale compared to neural connectivity].


The result is that we have a great deal of knowledge of tract level
connectivity (the connection of groups of neurons to other groups of neurons
via parallel sets of axons]. And we know nearly the full connectivity diagram
of certain easily studied areas, like the cerebellar cortex, and perhaps the
primary motor cortex.  And we know a great deal about the pattern of incoming
connections to most major neuron types even where we do not know the origin
of all of the inputs (that is how many synapses they have, and how they
are distributed about the cell).

In fact it is at the level of connectivity that we have the most to learn about
neuronal function.  That along with certain aspects of learning.


