Acknowledgments

The author thanks Shihua Wen, University of Maryland's Department of Mathematics, for running the simulations shown in Figs. 6 and 7. The author's computational work summarized herein has been supported in part by INSERM and the National Institutes of Health.

FIGURES (.EPS AND HIGH-QUALITY .JPEG)

Figures are provided in both .eps and .jpeg format in the CD. They were generated in Matlab and filtered using Abobe Illustrator.

MEDIA (MPEG)

Procedure Used to Generate the MPEG Files:

In the CD disk, there are six (6) mpeg files, the file names represent the simulated tasks, which are described below. The frames in format .avi were generated by the computational model written in MatLab's Simulink. The .avi files are generated by a shareware named "HyperCam" produced by Hypererionics Technology (www.hperionics.com). The mpeg files were obtained using the freeward softward "avi2meg" written by USH (www.ush.de). All the movies are recorded at a rate of 30 frames per second.

Description of Movies:

noseControl (duration: 1:48): Simulation shows the end-pont trajectories during the finger-to-nose task. A three segments arm is shown. These segments are linked by the shoulder, elbow, and wrist joints. This simulation of an intact (Control) network shows almost linear trajectories.

nose PD (duration: 1:49): This movie shows the performance of the computer model after simulating severe PD. In this simulation, the movement becomes slower, discrete, and noisy. Moreover, some of the targeted movements do not reach the nose.

noseAPD (duration: 1:51): This movie shows the finger-to-nose simulations after damage to the fronto-parietal network involved in sensorimotor trnsformations for reaching, which simulated APD. The end-point trajectories become irregular, coarse, fragmented, and dyscoordinated.

slicingControl (duration: 2:03): This clip shows a simulation of the "bread slicing" gesture as seen from directly above. The rectangle represents the loaf of bread. Note that there were not constrains on the way the virtual arm was supposed to produce the gesture. Note that during the repetitive movement the wrist joint was initially slightly flexed, but gradually became extended. This illustrates the fact that in a redundant arm there are many possible arm configurations that can be used to move the end point to a spatial target or along a given spatial trajectory.

slicingPD (duration: 2:03): The PD simulation shows reduced range of motion for all joints, discontinuous movements, and a difficulty in generating the repetitive slicing gesture. In this particular simulation, the wrist is in the extended position from the onset of the movement.

slicing APD (duration 2:03): This video shows the slicing gesture task after simulated APD. This simulation shows production errors as the arm fails to move the end point along the desired slicing trajectory. This resulted in highly disrupted spatial and temporal organization.

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