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Deficits in compensatory trajectory adjustments after unilateral sensorimotor stroke.
B E Fisher1, C J Winstein, M R Velicki
1Department of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles 90033, USA. bfisher@hsc.usc.edu
Experimental Brain Research
|July 7, 2000
Summary
Individuals with unilateral stroke show impaired compensatory adjustments in aiming movements, not planning deficits. This highlights the sensorimotor cortex's role in real-time movement correction.
Area of Science:
- Neuroscience
- Motor Control
- Rehabilitation Science
Background:
- Previous research indicated similar amplitude specification for goal-directed aiming movements in individuals with and without unilateral sensorimotor (SM) lesions.
- However, individuals with SM lesions exhibited reduced accuracy in unpredictable conditions, suggesting potential deficits in movement planning or adjustment.
- Compensatory adjustments and premovement planning are known to be crucial for accuracy in targeted force responses.
Purpose of the Study:
- To apply a statistical model to previous data to determine if accuracy differences in unilateral stroke patients stem from deficits in premovement planning, compensatory adjustments, or both.
- To investigate the role of the ipsilateral (intact) sensorimotor hemisphere in the premovement planning and execution of aiming movements.
Main Methods:
- Compared six subjects with unilateral stroke to matched control subjects in a timed-response movement paradigm.
- Subjects performed forearm flexion/extension to reach targets of varying sizes (20 or 45 degrees) in predictable or unpredictable sequences.
- Utilized multiple regression analysis on displacement and velocity data to assess the contributions of premovement planning and compensatory adjustments to end-point accuracy.
Main Results:
- In predictable conditions, premovement planning contributed more to final position in stroke subjects (0.50) than controls (0.36).
- No group differences were observed in the contribution of planning to accuracy in unpredictable conditions (0.54 vs. 0.45).
- Compensatory adjustments accounted for a significantly smaller percentage of final position variability in stroke subjects (0.09) compared to controls (0.25) across both conditions.
Conclusions:
- Reduced accuracy in unilateral stroke patients is primarily due to deficits in compensatory adjustments, not premovement planning.
- The ipsilateral sensorimotor hemisphere plays a significant role in the premovement planning of aiming actions.
- Sensorimotor areas are critical for preparing and implementing corrective actions during the unfolding of pre-planned movements.