Motor Patterns: BBS Call for Commentators

Stevan Harnad harnad at phoenix.Princeton.EDU
Mon Jul 1 11:36:56 EST 1991


Below are the abstracts of two forthcoming target articles on movement
and the motor system that have been accepted for publication in
Behavioral and Brain Sciences (BBS), an international,
interdisciplinary journal that provides Open Peer Commentary on
important and controversial current research in the biobehavioral and
cognitive sciences. Commentators must be current BBS Associates or
nominated by a current BBS Associate. To be considered as a commentator
on either of these articles (specify which, or both), to suggest other
appropriate commentators, or for information about how to become a BBS
Associate, please send email to:

harnad at clarity.princeton.edu  or harnad at pucc.bitnet        or write to:
BBS, 20 Nassau Street, #240, Princeton NJ 08542  [tel: 609-921-7771]

To help us put together a balanced list of commentators, please give
some indication of the aspects of the topic on which you would bring
your areas of expertise to bear if you were selected as a commentator.
A nonfinal draft of the full text of both articles is available for
inspection by anonymous ftp according to the instructions that follow
after the two abstracts.
____________________________________________________________________
Target Article #1 (Golani):

The Mobility Gradient and the Organization of Vertebrate Movement

			Ilan Golani
			Department of Zoology
			Tel Aviv University
			Ramat Aviv, Israel

Keywords: Movement notation, language, gestalt  perception,  play,
motor  development, ritualized fighting, drug-induced  stereotypies,
apomorphine, amphetamine, quinpirole, exploratory behavior.

Abstract: Ordinary language can prevent us from seeing the organization
of whole-animal movement. This may be why the search for behavioral
homologies has not been as fruitful as the founders of ethology had
hoped. The Eshkol-Wachman (EW) movement notational system can reveal
shared movement patterns that are undetectable in the kinds of informal
verbal descriptions of the same behaviors that are in current use.
Rules of organization that are common to locomotor development,
agonistic and exploratory behavior, scent marking, play, and
dopaminergic drug-induced stereotypies in a variety of vertebrates
suggest that behavior progresses along a "mobility gradient" from
immobility to increasing complexity and unpredictability. A progression
in the opposite direction, with decreasing spatial complexity and
increased stereotypy, occurs under the influence of the nonselective
dopaminergic drugs apomorphine and amphetamine and partly also the
selective dopamine agonist quinpirole. The behaviors associated with
the mobility gradient appear to be mediated by a family of basal
ganglia-thalamocortical circuits and their descending output stations.
Because the small number of rules underlying the mobility gradient
account for a large variety of behaviors, they may be related to the
specific functional demands on these neurological systems. The EW
system and the mobility gradient model should prove useful to
ethologists and neurobiologists.
____________________________________________________________________
Target Article #2 (Flanders):

EARLY STAGES IN A SENSORIMOTOR TRANSFORMATION

M. Flanders, S.I.H. Tillery, J. F. Soechting

Department of Physiology
University of Minnesota
Minneapolis, MN 55455

KEYWORDS: Sensorimotor transformation; Arm movement; Vision;
Kinesthesis; Movement kinematics

ABSTRACT: We present a model for several early stages of the
sensorimotor transformations involved in targeted arm movement. In
psychophysical experiments, human subjects pointed to the remembered
locations of randomly placed targets in three-dimensional space. They
made consistent errors in distance and from these errors, stages in the
sensorimotor transformation were deduced. When subjects attempted to
move the right index finger to a virtual target they consistently
undershot the distance of the more distal targets. Other experiments
indicated that the error was in the sensorimotor transformation rather
than in the perception of distance. The error was most consistent when
evaluated using a spherical coordinate system based at the right
shoulder, indicating that the neural representation of target
parameters is transformed from a retinocentric representation to a
shoulder-centered representation. According to the model, the error in
distance is due to the neural implementation of a linear approximation
in the algorithm to transform shoulder-centered target parameters into
a set of arm orientations appropriate for placing the finger on the
target. The transformation to final arm orientations places visually
derived information into a frame of reference where it can readily be
combined with kinesthetically derived information about initial arm
orientations. The combination of these representations of initial and
final arm orientations could give rise to the representation of
movement direction recorded in the motor cortex by Georgopoulos and his
colleagues. Later stages, such as the transformation from kinematic
(position) to dynamic (force) parameters, or to levels of muscle
activation, are beyond the scope of the present model.

--------------------------------------------------------------

To help you decide whether you would be an appropriate commentator for
either of these articles, a (nonfinal) draft of each is retrievable by
anonymous ftp from princeton.edu according to the instructions below
(the filenames are bbs.golani and bbs.flanders -- golani is there
already but flanders will only be available in a few days). Please do
not prepare a commentary on these drafts. Just let us know, after
having inspected them, what relevant expertise you feel you would bring
to bear on what aspect of the article, if you were selected as
commentator. (Please specify #1 (Golani), #2 (Flanders) or both.)

---------------------------------------------------------------
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-- 
Stevan Harnad  Department of Psychology  Princeton University
harnad at clarity.princeton.edu / harnad at pucc.bitnet / srh at flash.bellcore.com 
harnad at learning.siemens.com / harnad at elbereth.rutgers.edu / (609)-921-7771



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