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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 2 Shows Bilateral Adaptation to a Constant Force Field in the One-Cursor ConditionThe initial direction error of the perturbed hand (A) and unperturbed hand (B) in normal (solid line) and catch (dashed line) trials. Results are averaged across participants, hands, and force fields. Error bars indicate the between-subject standard error of the mean (SEM).
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fig4: Experiment 2 Shows Bilateral Adaptation to a Constant Force Field in the One-Cursor ConditionThe initial direction error of the perturbed hand (A) and unperturbed hand (B) in normal (solid line) and catch (dashed line) trials. Results are averaged across participants, hands, and force fields. Error bars indicate the between-subject standard error of the mean (SEM).

Mentions: So that the changes in adaptation could be confirmed, participants in experiment 2 (n = 8) adapted for 80 trials to a velocity-dependent force field of a constant direction applied to one of the hands. The perturbed hand (Figure 4A) quickly adapted to the large initial errors. This can also be seen in the change of initial direction in catch trials, in which no force field was applied (dashed line). In the two-cursor condition, adaptation was restricted to the perturbed hand. In the one-cursor condition, however, the unperturbed hand (Figure 4B) also changed its initial direction, such that it opposed the force field [t(7) = 7.89, p < .001], allowing the perturbed hand to adapt less than in the two-cursor condition [t(7) = 2.67, p = 0.032].


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

Diedrichsen J - Curr. Biol. (2007)

Experiment 2 Shows Bilateral Adaptation to a Constant Force Field in the One-Cursor ConditionThe initial direction error of the perturbed hand (A) and unperturbed hand (B) in normal (solid line) and catch (dashed line) trials. Results are averaged across participants, hands, and force fields. Error bars indicate the between-subject standard error of the mean (SEM).
© Copyright Policy
Related In: Results  -  Collection

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

fig4: Experiment 2 Shows Bilateral Adaptation to a Constant Force Field in the One-Cursor ConditionThe initial direction error of the perturbed hand (A) and unperturbed hand (B) in normal (solid line) and catch (dashed line) trials. Results are averaged across participants, hands, and force fields. Error bars indicate the between-subject standard error of the mean (SEM).
Mentions: So that the changes in adaptation could be confirmed, participants in experiment 2 (n = 8) adapted for 80 trials to a velocity-dependent force field of a constant direction applied to one of the hands. The perturbed hand (Figure 4A) quickly adapted to the large initial errors. This can also be seen in the change of initial direction in catch trials, in which no force field was applied (dashed line). In the two-cursor condition, adaptation was restricted to the perturbed hand. In the one-cursor condition, however, the unperturbed hand (Figure 4B) also changed its initial direction, such that it opposed the force field [t(7) = 7.89, p < .001], allowing the perturbed hand to adapt less than in the two-cursor condition [t(7) = 2.67, p = 0.032].

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
Related in: MedlinePlus