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Newsgroups: bit.listserv.csg-l
Date:         Tue, 15 Dec 1992 00:24:18 -0600
From:         Tom Bourbon <TBOURBON@BEACH.UTMB.EDU>
Subject:      Re: tom' post

From: Tom Bourbon (921215  00:19  CST)

Mark William Olson  (Mon, 14 Dec 1992 11:21:10 CST)

>Subject:      tom' post

First, you have my deepest sympathy for the many frustrating hours
you describe -- banging out long replies on a bad on-line editor,
only to see them vaporize!  I spent many unpleasant sessions like
that at my former university.

Now for one of your posts.

>Ok, I just read Tom's long post and realize that there is a
>misunderstanding  about what I am saying.  Did I say that the
>clinical report was a CHALLENGE to  PCT?  If so, it is not what I
>meant.  I meant that here is a perfect  opportunity for PCT to get
>involved- ...

My mistake.  I was picking up on phrases which I thought meant that
if we did not use what is known about the brain, PCT could not
advance much farther.

As for "a perfect opportunity for PCT to get involved," so far no
reviewer or editor of manuscripts from this lab, on imaging brain
structure and function, has tolerated the slightest suggestion that
behavior is purposive or that it controls perception?  Neuroscience
is not waiting for us with open arms!

>-I knew when I first saw the videotape of  the patient that it was
>a problem at the Relationship level--just like Tom  said.
>So....since we believe it is a Relationship problem and we know
>that  there is a bilateral lesion to the superior parietal area,
>then lets start  mapping our hierarchy.

I don't follow you here.  I am serious.  Exactly what are we
supposed to map onto what?  From the case you described, what do we
know about the superior parietal area (SPA)?  Which portion, or
portions, of the SPA should we consider, and how, specifically,
does the SPA figure in the man's control of relationships?

According to reports, in the video the man came close to reaching
the comb then stopped short.  In my post I described simulations of
disturbances to three different parts of a loop that controls
relationships.  All three disturbances could lead to a model that
stops short of reaching a target.  I suggested that if the man's
lesions produced effects like those of any one of the disturbances
in my simulations, then those effects might have produced the
behavioral results seen in the tape.

As I said in my post (Tom Bourbon  921214 01:30 CST)

>Did the man's lesions alter or disturb a reference signal, making
>it negative compared to what it was before?  Did the lesions add
>positive disturbance to an error signal or a perceptual signal?
>Did the lesions destroy one of the functions in a control system,
>or modify its workings, or disturb or disrupt a path carrying one
>of the signals in a control system?  Knowing that a lesion was in
>some general part of the brain, and that outward appearances of
>the person's behavior changed, tells us nothing specific about the
>reasons for the changes; but the process of modeling and
>simulating the control of relationships raises some possible
>explanations that, to my knowledge, neuroscientists and
>neuropsychologists have not considered.

I am not certain how the information about this fascinating
clinical case might guide us in mapping between brain function and
a PCT hierarchy.  Deficits like those in the tape might be produced
by any one of several changes in brain-as-control-system.  Which of
those possible changes, if any, might have been produced by the
lesions?  Or if none of the disturbances I modeled resembled the
real causes of the man's problems, which other portions of the
control loop might have been altered by his lesions, and how were
they altered?  Unless we know that, we do not know which label to
place at the SPA location on the "map."

>We cannot map the hierarchy without neuroscience  data--that seems
>very clear--how else will you know where some function occurs
>unless you know about what happens when areas are disabled (or
>brain scan  data)?

How can there be a science of brain function if a majority of brain
scientists do not at least occasionally examine the possibility
that, by their behavior, organisms control many of their
perceptions and that they incidentally control the states of
certain variables in their environments?

Seeing deficits as sequelae of specific injuries, and seeing images
in brain scans during certain kinds of performance, cannot
legitimately be taken as meaning that some "function" occurs in a
given place.  In most cases, the alleged "functions" are too poorly
defined to be taken seriously, but they are often taken very
seriously in neuroscience and neuropsychology.  Bill Powers
discussed that point at length in an earlier reply to you -- the
network citation is lost to me.

PCT modelers CAN work at determining whether control occurs, and if
so, whether it is best described and modeled as though produced by
hierarchical perceptual control systems.  If control occurs and can
be modeled that way, the results of our effort might inform
neuroscience.  I offered my simulations as a modest example of how
we might go about that project.

>I don't think we disagree very much --I think we agree alot.  My
>only  disagreement is to think that you can do it ONLY topo-down.
>You gotta have  both.  The bottom limits the top ad the top inform
>the bottom.

I do not understand what you mean.  You gotta have both of what?
Is PCT "top-down" and if so what does that mean?  I don't know.  Is
neuroscience "bottom-up?"  If so, I truly do not understand what
that means.

I am happy that you raised these topics (control of error;
neuroscience and PCT) on the net.  Keep plugging away at that messy
screen editor!

Until later,

Tom Bourbon                             e-mail:
Magnetoencephalography Laboratory       TBOURBON@UTMBEACH.BITNET
Division of Neurosurgery, E-17          TBOURBON@BEACH.UTMB.EDU
University of Texas Medical Branch      PHONE  (409) 763-6325
Galveston, TX 77550                     FAX    (409) 762-9961 USA
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