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Actions and consequences in bimanual interaction are represented in different coordinate systems
Paul M Bays1, Daniel M Wolpert
1Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London WC1N 3BG, United Kingdom. p.bays@ion.ucl.ac.uk
Summary
The human body actively predicts and counteracts forces generated by movement to maintain stability. This study shows that arm coordination learning adapts to new situations, representing movement and resulting force in different coordinate systems.
Area of Science:
- Neuroscience
- Motor Control
- Biomechanics
Background:
- Body part movement generates interaction forces that can destabilize other body parts.
- The body employs predictive mechanisms to actively oppose these destabilizing forces and maintain stability.
- These anticipatory mechanisms adapt to changes in the body or environment for accurate predictions.
Purpose of the Study:
- To examine the acquisition of novel predictive coordination between the arms.
- To investigate the coordinate systems used for internal transformation from movement to force.
- To understand how the brain represents arm movement and its resulting forces.
Main Methods:
- Subjects performed arm movements where a force on one hand was a consequence of the other hand's velocity.
- Adaptation to externally applied forces was assessed through practice.
- Generalization of learning to new joint configurations was tested to explore coordinate system representations.
Main Results:
- Subjects learned to stabilize a perturbed arm by predicting and opposing forces resulting from the other arm's movement.
- A dissociation was observed between the representation of the action (movement) and its consequence (force).
- Movement was represented in extrinsic coordinates (hand velocity), while the resulting force was represented in intrinsic, joint-based coordinates.
Conclusions:
- The human motor system can learn novel predictive coordination between limbs.
- Motor learning involves distinct neural representations for action and its sensory consequences.
- The brain utilizes different coordinate systems for representing movement and the forces it produces.