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The role of execution noise in movement variability
Robert J van Beers1, Patrick Haggard, Daniel M Wolpert
1Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, UK. r.vanbeers@erasmusmc.nl
Journal of Neurophysiology
|October 17, 2003
Summary
Movement variability originates from execution noise, not planning. This study shows execution noise in motor commands significantly impacts goal-directed movements, influencing endpoint accuracy and trajectory curvature.
Area of Science:
- Neuroscience
- Motor Control
- Biomechanics
Background:
- Variability in goal-directed movements is a complex phenomenon.
- Potential sources include target localization, movement planning, and execution.
- Understanding the primary source of this variability is crucial for motor control research.
Purpose of the Study:
- To investigate the contribution of movement execution noise to the variability of goal-directed movements.
- To differentiate between noise from movement planning and execution.
Main Methods:
- Subjects performed center-out reaching tasks to visual targets with unseen hands.
- Experiments minimized variability from localization and planning, focusing on execution.
- Variability in endpoints and initial movement direction was analyzed across 32 directions and varying movement extents.
Main Results:
- Movement endpoint and initial direction variability systematically changed with movement direction.
- Longer movements showed systematic curvature, with endpoint variability aligned with the latter trajectory.
- Observed variability was well-explained by noise in movement execution, not planning.
Conclusions:
- Movement execution noise is a significant contributor to overall movement variability.
- A combination of signal-dependent/independent amplitude noise and temporal noise in motor commands explains observed patterns.
- Execution noise accounts for a substantial proportion of variability in goal-directed movements.