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Saccade adaptation in response to altered arm dynamics.
Thrishantha Nanayakkara1, Reza Shadmehr
1Laboratory for Computational Motor Control, Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.
Journal of Neurophysiology
|December 11, 2003
Summary
The brain uses an adaptable internal model to predict limb position, compensating for sensorimotor delays. This model integrates proprioceptive feedback to estimate hand position for stable motor control.
Area of Science:
- Neuroscience
- Motor Control
- Systems Neuroscience
Background:
- Sensorimotor pathways have delays, challenging stable error feedback control.
- The brain maintains limb stability despite these delays, suggesting predictive mechanisms.
- Internal models of limb dynamics are hypothesized to aid in predicting limb position.
Purpose of the Study:
- To test if hand position estimation, via saccades, relies on an adaptable internal model of arm dynamics.
- To investigate how the brain accounts for altered arm dynamics during motor control.
Main Methods:
- Perturbing the unseen hand with a force pulse and observing saccade generation.
- Altering arm dynamics predictably or unpredictably post-perturbation.
- Analyzing saccade amplitude and position relative to hand movement.
Main Results:
- Saccades were generated as unbiased estimates of real-time hand position following perturbations.
- Saccade amplitudes adapted to reflect predictable changes in arm dynamics.
- This adaptation suggests the internal model adjusts to altered limb behavior.
Conclusions:
- The brain integrates proprioceptive feedback into an adaptable internal model.
- This model computes real-time hand position in eye-centered coordinates.
- This predictive mechanism is crucial for maintaining limb stability despite sensorimotor delays.