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From: Sound_movements@muwayb.ucs.unimelb.edu.au (Garry Jolley-Rogers)
Subject: Re: Spider brains
Message-ID: <Sound_movements-2207951956450001@zakari.psych.unimelb.edu.au>
Sender: news@cs.mu.OZ.AU (CS-Usenet)
Organization: Dept of Psychology
References: <3u1bii$a6r@PEAK.ORG> <3u27uc$ooc@newsbf02.news.aol.com>
Date: Fri, 21 Jul 1995 09:57:27 GMT
Lines: 53

In article <3u27uc$ooc@newsbf02.news.aol.com>, jxidus@aol.com (JXidus) wrote:

> In article <3u1bii$a6r@PEAK.ORG>, zeiglea@PEAK.ORG (Anthony Zeigler)
> writes:
> >In article <3u0rp2$bok@jan.et.byu.edu>, Dan Ventura  <dan@axon> wrote:
> >>I remember someone making a claim a few weeks ago that arachnids (at
> least
> >some
> >>of them?) had only 8 neurons.  Does anybody have a reference for this?
> >I see this as highly unlikely. One of the most studied animals in neural
> >research is a worm with 130 very large neurons. Since worms are by far
> >simplier creatures than arachnids it is highly unlikely there is any
> truth
> >to this claim.
> >Tony Zeigler
> 
> I think I agree with Anthony.  An article I read (sorry, can't place it),
> mentioned simulation of a "nematode, having only a few hundred neurons". 
> I'm not too familiar with nematodes, but I would think arachnids would
> have far more complex brains.
> My two cents... :)
> 
> Jeremy Weatherford
> jxidus@aol.com




No....arachnids have of the order of several thousand neurons if not more
depending on size and species.  Because there are (relative to
verterbrates) so  few neurons. It is common to identify and label cells
under study. The outlandish claim above is probably a misreading of a
article that dealt with a part  of a arachnid's nervous system.  

My guess is that there would be more than 8 neurons in each leg segment of
an arachnid.

And, BTW  it is not just the number of neurons that matter in invertebrate
nervous systems ( & probably our own as well). It has been argued (rather
convinvingly to my own mind) that the parts of some fly neurons my work in
isolation from each other.

There are times that I find the lack of knowledge of biology of people who
work with artificial neural nets exasperating. Certainly, there are some
outlandish claims and assumptions out there.

GJR

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Garry Jolley-Rogers
Dept of Psychology 
University of Melbourne
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