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Manual Tracking Performance in Patients with Cerebellar Incoordination: Effects of Mechanical Loading

Published online by Cambridge University Press:  18 September 2015

Betty-Lynn Morrice ,
Werner J. Becker ,
J.A. Hoffer  and
Robert G. Lee
Betty-Lynn Morrice
Affiliation:
Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada
Werner J. Becker
Affiliation:
Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada
J.A. Hoffer
Affiliation:
Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada
Robert G. Lee*
Affiliation:
Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada
*
Department of Clinical Neurosciences, Foothills Hospital, 1403 - 29th Street N.W., Calgary, Alberta, Canada T2N 2T9
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Abstract:

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Manual tracking performance was studied in five patients with cerebellar incoordination due to unilateral cerebellar hemisphere lesions. The subjects were required to track a target on an oscilloscope screen by moving a cursor controlled by flexion-extension movements of the wrist. In comparison to normal subjects, the cerebellar patients, using their clinically affected arm, demonstrated irregular tracking patterns with inappropriate accelerations and decelerations, numerous high velocity peaks of movement, and an increased time lag between the cursor and the target.

The addition of a viscous load provided by feeding back wrist velocity to a torque motor coupled to the apparatus resulted in significant improvement in tracking performance and suppression of the high velocity peaks. Increasing elastic stiffness by feeding back wrist position or inertial load by adding weights to the hand did not improve performance on this task. It is proposed that a hypotonic cerebellar limb behaves like an underdamped mechanical system. The addition of viscous loads helps restore more normal damping during voluntary movements of the arm.

Résumé:

RÉSUMÉ:

La poursuite manuelle a été étudiée chez cinq patients atteints d'incoordination cérébelleuse due à des lésions unilatérales d'un hémisphère cérébelleux. Les sujets devaient poursuivre une cible sur un écran d'oscilloscope en déplaçant un curseur contrôlé par des mouvements de flexion et d'extension du poignet. Par rapport à des sujets normaux, les patients avec atteinte cérébelleuse exécutaient des tracés de poursuite irréguliers avec des accélérations et décélérations inappropriées, de nombreuses pointes de mouvement de haute vélocité et une augmentation du délai entre le curseur et la cible. L'ajout d'une charge visqueuse, provenant de la vélocité du poignet agissant sur un moteur couplé à l'appareillage, a résulté en une amélioration significative dans l'exécution de la poursuite et une suppression des pointes de haute vélocité. Ni une augmentation de la rigidité élastique produite par la localisation de la position du poignet, ni une augmentation de la charge d'inertie produite par l'ajout de poids à la main n'ont amélioré l'exécution de la tâche. Nous proposons qu'un membre présentant une hypotonie cérébelleuse se comporte comme un système mécanique sous-amorti. L'addition de charges visqueuses aide à rétablir un amortissement plus normal pendant les mouvements volontaires du bras.

Type
Original Articles
Information
Canadian Journal of Neurological Sciences , Volume 17 , Issue 3 , August 1990 , pp. 275 - 285
Copyright
Copyright © Canadian Neurological Sciences Federation 1990

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