Two studies of voluntary movement in Parkinson's disease were carried out. In the first study, both parkinsonians and age-matched controls performed unconstrained prehensile movements in which subjects produced reaching and grasping (hand opening/closing) movements under varying conditions of movement amplitude, speed and object size. The act of prehension requires the intersegmental coordination of limb transport and grasp trajectories. Although parkinsonians were slower overall than controls, patients and controls similarly adjusted the spatial and temporal characteristics of their limb movement and grasp in response to changes in task demands. All groups showed increases in the speed of limb transport, the speed of hand opening and began hand opening proportionately earlier at faster movement speeds. All groups similarly increased hand opening velocity and initiated grasp earlier for smaller amplitude movements. Likewise, grasp was initiated earlier when reaching for wider objects. However, in contrast to controls, the onset time of hand opening during limb transport was delayed in these patients and was found to be more closely coupled with the timing of limb transport than in the controls. Moreover, patients showed greater curvature in their motion paths at the wrist during limb transport suggesting that the timing of joint motion (shoulder and elbow) may be different in these patients as well. Underlying differences between the groups in the temporal sequencing of movement are discussed. / In a second study, parkinson and control subjects performed continuous tracking movements in pursuit of sinusoidal and constant-speed target trajectories varying in frequency and amplitude. This task provided explicit temporal and spatial accuracy constraints by requiring subjects to reproduce the precise trajectory (i.e., velocity profile) of target movement. The results show that patients, similar to controls, were capable of modifying peak movement velocity while varying their times to reversal (i.e., movement durations) in response to changes in the movement time requirements of target motion. Indeed, both patients and controls were shown to alter the timing of movement deceleration in order to maintain their movement durations within the temporal limits of target movement. In contrast to controls, patients show progressive reduction in endpoint accuracy (undershooting the target) and, hence, reduced movement amplitudes, over the course of the trial. However, when endpoint accuracy requirements were reduced, by providing mechanical constraints on movement amplitude, patients were able to increase movement amplitudes while satisfying the temporal requirements of the task. These results are interpreted in terms of tradeoffs in performance between competing spatial and temporal demands of pursuit tracking. The significance of movement accuracy constraints on motor function in parkinsonian performance is discussed.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.74245 |
| Date | January 1989 |
| Creators | Zackon, Warren T. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Psychology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000966461, proquestno: AAINL57306, Theses scanned by UMI/ProQuest. |
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