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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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Experiment 1 Shows Bilateral Movement Corrections in the One-Cursor Condition(A) In the two-cursor condition, participants reached for two separate targets. In the one-cursor condition, they reached with both hands to move a common cursor to a single target. One of the hands was perturbed with a leftward (red) or rightward (blue) force field or was unperturbed (black).(B) Predicted movement trajectories based on the optimal control policy.(C) Movement trajectories observed in experiment 1, averaged across participants and hands.(D) The y velocity (dashed line) and x velocity (red, blue, and black solid lines) of the perturbed hand.(E and F) The x velocity of the unperturbed hand with (E) and without (F) visual feedback shows the onset of the correction in the one-cursor condition. The shaded area indicates the across-subject standard error (SE).
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fig1: Experiment 1 Shows Bilateral Movement Corrections in the One-Cursor Condition(A) In the two-cursor condition, participants reached for two separate targets. In the one-cursor condition, they reached with both hands to move a common cursor to a single target. One of the hands was perturbed with a leftward (red) or rightward (blue) force field or was unperturbed (black).(B) Predicted movement trajectories based on the optimal control policy.(C) Movement trajectories observed in experiment 1, averaged across participants and hands.(D) The y velocity (dashed line) and x velocity (red, blue, and black solid lines) of the perturbed hand.(E and F) The x velocity of the unperturbed hand with (E) and without (F) visual feedback shows the onset of the correction in the one-cursor condition. The shaded area indicates the across-subject standard error (SE).

Mentions: Optimal control theory [3] predicts that the coordination of movements depends on task goals. Here, I show that humans alter bimanual feedback control according to this prediction. In experiment 1, participants (n = 10) performed a bimanual reaching task in separate sessions under two conditions (FigureĀ 1A). In the two-cursor condition, participants simultaneously moved two cursors, one with each hand, toward separate visual targets. In the one-cursor condition, participants performed physically similar reaching movements but moved a single cursor, presented at the average position of the two hands, to a single target. So that feedback control could be tested, in half of the trials, a randomly selected hand was perturbed with a velocity-dependent leftward or rightward force field [4].


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

Diedrichsen J - Curr. Biol. (2007)

Experiment 1 Shows Bilateral Movement Corrections in the One-Cursor Condition(A) In the two-cursor condition, participants reached for two separate targets. In the one-cursor condition, they reached with both hands to move a common cursor to a single target. One of the hands was perturbed with a leftward (red) or rightward (blue) force field or was unperturbed (black).(B) Predicted movement trajectories based on the optimal control policy.(C) Movement trajectories observed in experiment 1, averaged across participants and hands.(D) The y velocity (dashed line) and x velocity (red, blue, and black solid lines) of the perturbed hand.(E and F) The x velocity of the unperturbed hand with (E) and without (F) visual feedback shows the onset of the correction in the one-cursor condition. The shaded area indicates the across-subject standard error (SE).
© Copyright Policy
Related In: Results  -  Collection

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

fig1: Experiment 1 Shows Bilateral Movement Corrections in the One-Cursor Condition(A) In the two-cursor condition, participants reached for two separate targets. In the one-cursor condition, they reached with both hands to move a common cursor to a single target. One of the hands was perturbed with a leftward (red) or rightward (blue) force field or was unperturbed (black).(B) Predicted movement trajectories based on the optimal control policy.(C) Movement trajectories observed in experiment 1, averaged across participants and hands.(D) The y velocity (dashed line) and x velocity (red, blue, and black solid lines) of the perturbed hand.(E and F) The x velocity of the unperturbed hand with (E) and without (F) visual feedback shows the onset of the correction in the one-cursor condition. The shaded area indicates the across-subject standard error (SE).
Mentions: Optimal control theory [3] predicts that the coordination of movements depends on task goals. Here, I show that humans alter bimanual feedback control according to this prediction. In experiment 1, participants (n = 10) performed a bimanual reaching task in separate sessions under two conditions (FigureĀ 1A). In the two-cursor condition, participants simultaneously moved two cursors, one with each hand, toward separate visual targets. In the one-cursor condition, participants performed physically similar reaching movements but moved a single cursor, presented at the average position of the two hands, to a single target. So that feedback control could be tested, in half of the trials, a randomly selected hand was perturbed with a velocity-dependent leftward or rightward force field [4].

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