The study investigated how the motor system coordinates redundant body movements to adapt to visual perturbations in a bimanual stick manipulation task. The key findings are:
Participants adopted a stereotypical strategy of flexibly changing the tilt angle of the stick depending on the direction of the stick tip movement, reflecting a baseline relationship between the two. This relationship likely emerged from an optimization process to minimize movement distance.
When an end-effector relevant perturbation (visual rotation of the stick tip) was introduced, participants adapted by changing the stick tilt angle as if they were voluntarily aiming at the adapted direction, while the tip movement direction remained at the baseline level. This suggests the motor system uses the baseline relationship as a scaffold to guide implicit adaptation.
Even when an end-effector irrelevant perturbation (stick tilt angle) was introduced, the motor system attempted to correct the stick tilt error, which led to undesirable errors in the tip movement direction. This indicates the motor system predicts the visual feedback of the end-effector irrelevant dimension and tries to eliminate any dissociation between the observed and predicted states.
The adaptation patterns were influenced by the combination of end-effector relevant and irrelevant perturbations, suggesting an interaction between the two adaptation processes constrained by the baseline relationship.
Overall, the findings provide a new understanding that the baseline relationship between the end-effector and redundant body movements plays a crucial role in how the motor system controls and implicitly adapts movement patterns in redundant systems.
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by Kobayashi,T.... at www.biorxiv.org 06-14-2023
https://www.biorxiv.org/content/10.1101/2023.06.13.544873v2Deeper Inquiries