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Frame-by-Frame Video Analysis of Idiosyncratic Reach-to-Grasp Movements in Humans
Published on: January 15, 2018
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Grasp-Based Functional Coupling Between Reach- and Grasp-Related Components of Forelimb Muscle Activity.
Shashwati Geed1,2,3, Peter L E van Kan1
1a Department of Kinesiology , University of Wisconsin-Madison , Wisconsin.
Journal of Motor Behavior
|September 3, 2016
Summary
Grasp type, not target location, dictates how forelimb muscles coordinate during reach-to-grasp actions. This finding reveals a grasp-based functional coupling in motor control, optimizing movement efficiency.
Area of Science:
- Neuroscience
- Biomechanics
- Motor Control
Background:
- Neuromotor systems exhibit redundancy, allowing multiple muscle combinations for a single movement.
- Understanding muscle selection during complex actions like reach-to-grasp is crucial for motor control research.
- Task constraints, such as grasp type and target location, are hypothesized to influence muscle synergy.
Purpose of the Study:
- To investigate whether grasp type or target location primarily drives muscle selection and synergistic coupling during reach-to-grasp movements.
- To elucidate the underlying neural control strategies for forelimb movements in the presence of neuromotor redundancy.
Main Methods:
- Electromyograms (EMGs) were recorded from 14-20 forelimb muscles in monkeys during reach-to-grasp tasks.
- Factor analysis was employed to identify underlying muscle components and their temporal activation patterns.
- Weighting and scaling coefficients of muscle components were analyzed to assess the influence of grasp type and target location.
Main Results:
- Factor analysis revealed 4-6 muscle components associated with either the transport/preshape phase or the grasp phase of the movement.
- Muscle component activation patterns showed greater similarity for movements sharing the same grasp type, irrespective of target location.
- Temporal coupling between transport/preshape and grasp components remained consistent, indicating invariant coordination.
Conclusions:
- Grasp type exerts a dominant influence on both the early (transport/preshape) and late (grasp) phases of reach-to-grasp movements.
- The findings support a grasp-centric model of motor control, where the intended grasp shapes the entire reach-to-grasp synergy.
- This study demonstrates a functional coupling of forelimb muscles based on the specific grasp requirements, optimizing motor execution.
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