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Optimal task-dependent changes of bimanual feedback control and adaptation.

Diedrichsen J - Curr. Biol. (2007)

Bottom Line: Adaptation, the influence of a perturbation onto the next movement, also depended on task goals.In the two-cursor condition, only the perturbed hand adapted to a force perturbation [2], whereas in the one-cursor condition, both hands adapted.These findings demonstrate that the central nervous system changes bimanual feedback control and adaptation optimally according to the current task requirements.

View Article: PubMed Central - PubMed

Affiliation: Wolfson Centre for Cognitive Neuroscience, School of Psychology, University of Wales, Bangor, Gwynedd LL57 2AS, United Kingdom. j.diedrichsen@bangor.ac.uk

ABSTRACT
The control and adaptation of bimanual movements is often considered to be a function of a fixed set of mechanisms [1, 2]. Here, I show that both feedback control and adaptation change optimally with task goals. Participants reached with two hands to two separate spatial targets (two-cursor condition) or used the same bimanual movements to move a cursor presented at the spatial average location of the two hands to a single target (one-cursor condition). A force field was randomly applied to one of the hands. In the two-cursor condition, online corrections occurred only on the perturbed hand, whereas the other movement was controlled independently. In the one-cursor condition, online correction could be detected on both hands as early as 190 ms after the start. These changes can be shown to be optimal in respect to a simple task-dependent cost function [3]. Adaptation, the influence of a perturbation onto the next movement, also depended on task goals. In the two-cursor condition, only the perturbed hand adapted to a force perturbation [2], whereas in the one-cursor condition, both hands adapted. These findings demonstrate that the central nervous system changes bimanual feedback control and adaptation optimally according to the current task requirements.

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Task-Dependent Changes in Correction and Adaptation Rates(A) Correction rate, the proportion of initial direction error corrected by the same (black) and other (gray) hand within the same trial. The predicted optimal correction rates are plotted as dotted lines.(B) Adaptation rate, the influence of an initial direction error onto the initial direction of the same (black) and other (gray) hand. Error bars indicate the between-subject standard error of the mean (SEM).(C) For the one-cursor condition only, the between-hand correction rate correlates significantly with the between-hand adaptation rate. Each data point represents one hand of one participant under either the visual-feedback or no-visual-feedback condition.
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fig2: Task-Dependent Changes in Correction and Adaptation Rates(A) Correction rate, the proportion of initial direction error corrected by the same (black) and other (gray) hand within the same trial. The predicted optimal correction rates are plotted as dotted lines.(B) Adaptation rate, the influence of an initial direction error onto the initial direction of the same (black) and other (gray) hand. Error bars indicate the between-subject standard error of the mean (SEM).(C) For the one-cursor condition only, the between-hand correction rate correlates significantly with the between-hand adaptation rate. Each data point represents one hand of one participant under either the visual-feedback or no-visual-feedback condition.

Mentions: The behavior of the participants followed closely this prediction (Figures 1C–1E, right). The kinematics of the movements during unperturbed movements was similar. However, starting at 190 ms, the unperturbed hand showed coordinated corrections; at this time, the lateral velocity started to depend significantly on the direction of the force applied to the other hand. As a quantitative measure of the amount of correction, I computed the proportion of the initial direction error corrected by each hand (Figure 2A). When going from the two- to the one-cursor condition, the between-hand correction rate increased, whereas the within-hand correction rate decreased, matching quantitatively the predictions of optimal control theory.


Optimal task-dependent changes of bimanual feedback control and adaptation.

Diedrichsen J - Curr. Biol. (2007)

Task-Dependent Changes in Correction and Adaptation Rates(A) Correction rate, the proportion of initial direction error corrected by the same (black) and other (gray) hand within the same trial. The predicted optimal correction rates are plotted as dotted lines.(B) Adaptation rate, the influence of an initial direction error onto the initial direction of the same (black) and other (gray) hand. Error bars indicate the between-subject standard error of the mean (SEM).(C) For the one-cursor condition only, the between-hand correction rate correlates significantly with the between-hand adaptation rate. Each data point represents one hand of one participant under either the visual-feedback or no-visual-feedback condition.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2230536&req=5

fig2: Task-Dependent Changes in Correction and Adaptation Rates(A) Correction rate, the proportion of initial direction error corrected by the same (black) and other (gray) hand within the same trial. The predicted optimal correction rates are plotted as dotted lines.(B) Adaptation rate, the influence of an initial direction error onto the initial direction of the same (black) and other (gray) hand. Error bars indicate the between-subject standard error of the mean (SEM).(C) For the one-cursor condition only, the between-hand correction rate correlates significantly with the between-hand adaptation rate. Each data point represents one hand of one participant under either the visual-feedback or no-visual-feedback condition.
Mentions: The behavior of the participants followed closely this prediction (Figures 1C–1E, right). The kinematics of the movements during unperturbed movements was similar. However, starting at 190 ms, the unperturbed hand showed coordinated corrections; at this time, the lateral velocity started to depend significantly on the direction of the force applied to the other hand. As a quantitative measure of the amount of correction, I computed the proportion of the initial direction error corrected by each hand (Figure 2A). When going from the two- to the one-cursor condition, the between-hand correction rate increased, whereas the within-hand correction rate decreased, matching quantitatively the predictions of optimal control theory.

Bottom Line: Adaptation, the influence of a perturbation onto the next movement, also depended on task goals.In the two-cursor condition, only the perturbed hand adapted to a force perturbation [2], whereas in the one-cursor condition, both hands adapted.These findings demonstrate that the central nervous system changes bimanual feedback control and adaptation optimally according to the current task requirements.

View Article: PubMed Central - PubMed

Affiliation: Wolfson Centre for Cognitive Neuroscience, School of Psychology, University of Wales, Bangor, Gwynedd LL57 2AS, United Kingdom. j.diedrichsen@bangor.ac.uk

ABSTRACT
The control and adaptation of bimanual movements is often considered to be a function of a fixed set of mechanisms [1, 2]. Here, I show that both feedback control and adaptation change optimally with task goals. Participants reached with two hands to two separate spatial targets (two-cursor condition) or used the same bimanual movements to move a cursor presented at the spatial average location of the two hands to a single target (one-cursor condition). A force field was randomly applied to one of the hands. In the two-cursor condition, online corrections occurred only on the perturbed hand, whereas the other movement was controlled independently. In the one-cursor condition, online correction could be detected on both hands as early as 190 ms after the start. These changes can be shown to be optimal in respect to a simple task-dependent cost function [3]. Adaptation, the influence of a perturbation onto the next movement, also depended on task goals. In the two-cursor condition, only the perturbed hand adapted to a force perturbation [2], whereas in the one-cursor condition, both hands adapted. These findings demonstrate that the central nervous system changes bimanual feedback control and adaptation optimally according to the current task requirements.

Show MeSH