Flatworms & Maze Memory

M.J. Stillman stillman at dendwrite.com
Mon Dec 9 10:47:02 EST 1996

Krister Eriksson wrote:
> In article <32A905B4.4124 at stratos.net> Dave York <dyork at stratos.net> writes:
> >Can anyone help me locate information on an experiment I vaguely recall
> >reading about years ago? Flatworms (?) were taught to execute a 2-D maze
> >then chopped up and fed to 2nd group of flatworms...
[original post snipped, like the donor flatworms]

> I have to use my memory for this one, since I don´t have any references handy.
> Planarian flatworms were put in a T-maze and they were somehow (attracted by
> food or repelled by some noxious chemical? I can´t remember) "learned" to
> always turn in the same direction. If these animals had their heads cut off,
> the newly regenerated head still knew in which direction to turn. And if the
> trained animals were chopped up and fed to untrained animals, the knowledge
> was transferred to the untrained animals. I think that these results were
> taken as support for the in those days commonly(?) held hypothesis that RNA is
> the carrier of memory.
> However, I read a review paper in which the author stated that most of
> these studies failed to take a very important factor into consideration: slime.
> The planarians give off mucus that forms a track in the same fashion as
> snails do. They also prefer mucus-covered areas over clean ones. Accordingly,
> the T-maze would soon have a mucus track in either direction, that could lead
> the worms to make the correct choice. My personal experience is that this
> mucus is insoluble in water and I once noted that it was still there after
> about one month in water containing washing detergent.
> Regards,
> Krister Eriksson
> Dept. Biology
> Åbo Akademi University
> Åbo, Finland

Wasn't there a science spoof journal called the "Worm Runners Digest?" 
I seem to recall reading this during some undergrad study breaks.  Maybe
similar to/ancestor of the JIR (Journal of Irreproducible Results)?

Krister is correct in that the original theory that RNA is the code for
memory storage was eventually discredited after being viewed as an
important discovery.

If anyone's interested, I have a citation for the original article (I
don't have the article itself, but this comes from Schneider & Tarshis,
2/e, 1980, one of my old Physio. Psych textbooks ):

McConnell, JV. 1962. Memory transfer through cannibalism in planarians. 
Journal of Neuropsychiatry 3 (Supplement no. 1): 542-548.

I like the notion that the slime track was responsible for the putative
"memory enhancement," but don't have a reference for it.  Perhaps
Krister or another NG reader would?  

Also, did they ever use a new T-maze for the memory test?  Some might
argue that this presents different environmental cues and would confound
the results, but this could be easily controlled.

S&T mention (p.451) that Hartry's group (published in Science, see
below) used two groups of "donor" planaria: one group trained to avoid
shock, the other group was just randomly shocked. RNA from both donor
types produced the transfer effect in the recipient planaria, suggesting
that shock itself, rather than learning/memory, changed the performance.

Hartry, AL et al. 1964. Planaria: memory transfer through cannibalism
re-examined.  Science 146: 274-275.

Please let me know if this post was helpful.  I look forward to
following this thread.  Good luck, all.

Michael J. Stillman, Ph.D.
DendWrite Communications
33 Dinsmore Avenue, Suite 602
Framingham, MA  01702
Tel/Fax: 508.875.7782

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