Movement kinematics during reaching in essential tremor.
2002
Hochschulschrift
Zugriff:
Essential tremor (ET), a condition where involuntary oscillations are present throughout movement, can be viewed as a model for examining how the central nervous system adapts to constant perturbations which might be expected to compromise motor performance. In addition, despite being twenty times more prevalent than, for example, Parkinson's Disease, the specific mechanism underlying ET is not definitively known. Thus, this study was designed to examine ET and the movement characteristics observed during goal-directed, reaching movements. Twenty-six control and ET subjects performed four tasks which differed in complexity: maintenance of a static upper limb posture, reach and point, reach and grasp, and obstacle clearance. During posture maintenance, three-dimensional (3D) tremor amplitude and frequency was examined. A 3D motion analysis system was used to record reaching movement kinematics under varying distance, target/object width and obstacle orientation conditions. Postural ET amplitude was greater than controls (p = 0.015) in all three movement planes. Postural ET plane-dependency was observed; ET amplitude was greater in the vertical and medial-lateral as compared to anterior-posterior planes (p = 0.001). Also, three postural ET amplitude patterns were observed suggesting a gradual synchronization of multiple tremor oscillators. ET subjects were consistently slower than controls in the reach and point (p = 0.001) and reach and grasp (p = 0.01) tasks, regardless of distance and target/object width, and in the clearance tasks (p = 0.004), regardless of obstacle orientation. Movement symmetry ratios (time to peak velocity to movement time 0.35) did not differ between groups regardless of task or condition. However, spatial variability in movement trajectory was much greater in the ET compared to the control group (p = 0.001). Regardless of task, ET subjects utilized safety margins that were consistently greater than safety margins utilized by control subjects. ET subjects had movement disorders other than tremor. Tremor, bradykinesia and highly variable spatial trajectories was evident in reaching movements performed by ET subjects implicating mild cerebellar pathology. Several future studies have been proposed to further elucidate the mechanism underlying ET.
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Movement kinematics during reaching in essential tremor.
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Autor/in / Beteiligte Person: | Larson, Cathy A. |
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Veröffentlichung: | 2002 |
Medientyp: | Hochschulschrift |
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