[From Rick Marken (2002.06.10.0930)]
Bill Powers (2002.06.06.1224 MDT) --
Concerning the Graziano et. al. paper, check out the reference from
Ranson
and Clark starting at the bottom of p. 121 in B:CP. Looks as if Ward
did a
very similar experiment prior to 1947.
I'm afraid I forgot to take a look at it this this weekend. But I did
think of something that _might_ be worth doing. Couldn't you reproduce
the Graziano et. al. results relatively easily in your "Little Man"
program? It might be neat to have a version of the Little Man where the
"user" could inject signals of various durations. These signals are the
equivalent of the electrical signals used by Graziano et al (and Ward,
too, I suppose). The signals (depending on their magnitude) specify the
x,y,z target location for the little man's fingertip.
The "surprising" finding in Graziano et. al. is that longer duration
signals lead to very different results when stimulating the same
cortical neurons than shorter duration signals. This variant of the
Little Man demo could show that this is precisely what results when the
stimulus signal is setting the reference for a perceptual input (eg.,
x,y,z finger at position). With short signals all the Little Man would
do is produce apparently purposeless "jerky" movements. With a longer
signal we should see what Graziano et. al. saw; smooth, purposeful
movements to a goal position.
I would do this myself but 1) you are a heck of a lot more familiar with
the Little Man code than I am and 2) I am actually working on another
modeling project (not baseball; something else that I think I'll
describe at the meeting) where I am successfully reproducing some very
interesting data using a simple two level PCT model.
Best regards
Rick
···
--
Richard S. Marken, Ph.D.
The RAND Corporation
PO Box 2138
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Santa Monica, CA 90407-2138
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E-mail: rmarken@rand.org