Two NIPS preprints on motor control

[Daniel Wolpert]

The following two papers will appear in G. Tesauro, D.S. Touretzky and
T.K. Leen, eds., "Advances in Neural Information Processing Systems
7", MIT Press, Cambridge MA, 1995. The papers combine computational
and psychophysical approaches to human motor control.

Daniel Wolpert
wolpert at psyche.mit.edu

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	     Forward dynamic models in human motor control:
		      Psychophysical evidence	

	   Daniel Wolpert, Zoubin Ghahramani & Michael Jordan
	       Department of Brain & Cognitive Sciences
		Massachusetts Institute of Technology
			 Cambridge, MA 02139

Based on computational principles, with as yet no direct experimental
validation, it has been proposed that the central nervous system (CNS)
uses an internal model to simulate the dynamic behavior of the motor
system in planning, control and learning.  We present experimental
results and simulations based on a novel approach that investigates
the temporal propagation of errors in the sensorimotor integration
process.  Our results provide direct support for the existence of an
internal model.


FTP-host: psyche.mit.edu
FTP-filename: /pub/wolpert/forward.ps.Z

URL: ftp://psyche.mit.edu/pub/wolpert/forward.ps.Z

8 pages long [163K compressed].
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	Computational structure of coordinate transformations:
			 A generalization study

	  Zoubin Ghahramani, Daniel Wolpert & Michael Jordan
	       Department of Brain & Cognitive Sciences
		Massachusetts Institute of Technology
			 Cambridge, MA 02139


One of the fundamental properties that both neural networks and the
central nervous system share is the ability to learn and generalize
from examples. While this property has been studied extensively in the
neural network literature it has not been thoroughly explored in human
perceptual and motor learning. We have chosen a coordinate
transformation system---the visuomotor map which transforms visual
coordinates into motor coordinates---to study the generalization
effects of learning new input--output pairs.  Using a paradigm of
computer controlled altered visual feedback, we have studied the
generalization of the visuomotor map subsequent to both local and
context-dependent remappings. A local remapping of one or two
input-output pairs induced a significant global, yet decaying, change
in the visuomotor map, suggesting a representation for the map
composed of units with large functional receptive fields. Our study of
context-dependent remappings indicated that a single point in visual
space can be mapped to two different finger locations depending on a
context variable---the starting point of the movement. Furthermore, as
the context is varied there is a gradual shift between the two
remappings, consistent with two visuomotor modules being learned and
gated smoothly with the context.


FTP-host: psyche.mit.edu
FTP-filename: /pub/wolpert/coord.ps.Z

URL: ftp://psyche.mit.edu/pub/wolpert/coord.ps.Z

8 pages long [218K compressed].