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Discordant Tasks and Motor Adjustments Affect Interactions between Adaptations to Altered Kinematics and Dynamics.

Arce F, Novick I, Vaadia E - Front Hum Neurosci (2010)

Bottom Line: We found a gradient of interaction effects based on perturbation direction and task discordance.We also found that force field and visuomotor rotation had mutual anterograde and retrograde effects.Such overlap does not necessarily imply competition of resources.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Neurobiology, The Institute for Medical Research Israel-Canada, Hadassah Medical School, Hebrew University Jerusalem, Israel.

ABSTRACT
Motor control and adaptation are multi-determinate processes with complex interactions. This is reflected for example in the ambiguous nature of interactions during sequential adaptation of reaching under kinematics and dynamics perturbations. It has been suggested that perturbations based on the same kinematic parameter interfere. Others posited that opposing motor adjustments underlie interference. Here, we examined the influence of discordances in task and in motor adjustments on sequential adaptations to visuomotor rotation and viscous force field perturbations. These two factors - perturbation direction and task discordance - have been examined separately by previous studies, thus the inherent difficulty to identify the roots of interference. Forty-eight human subjects adapted sequentially to one or two types of perturbations, of matched or conflicting directions. We found a gradient of interaction effects based on perturbation direction and task discordance. Perturbations of matched directions showed facilitation while perturbations of opposite directions, which required opposing motor adjustments, interfered with each other. Further, interaction effects increased with greater task discordance. We also found that force field and visuomotor rotation had mutual anterograde and retrograde effects. However, we found independence between anterograde and retrograde interferences between similar tasks. The results suggest that the newly acquired internal models of kinematic and dynamic perturbations are not independent but they share common neuronal resources and interact between them. Such overlap does not necessarily imply competition of resources. Rather, our results point to an additional principle of sensorimotor adaptation allowing the system to tap or harness common features across diverse sensory inputs and task contexts whenever available.

No MeSH data available.


Related in: MedlinePlus

Sequential adaptations to force fields and visuomotor rotations. Hand paths of representative subjects from each group following the A–B–A paradigm. The subplots are organized according to task (row) and direction of perturbations (column): double force field (A), matched force-rotation (B), opposite force field (C), non-matched force-rotation (D). Each subplot shows the average trajectories of early trials (trials 1–5, colored) and of late trials (trials 181–200, black) for tasks A and B performed on the first day-session and for retest on task A 24 h later. Hand paths, plotted from detected movement onset to movement end, show displacement from origin to a target at 90° (gray circle). Learned target direction was always at 90°. In (B), visuomotor rotation was counterclockwise and the required hand movement direction was towards a target at 45° (light gray circle) while in (D), rotation was clockwise and the required hand movement direction was towards a target at 135° (light gray circle). Note that trajectories correspond to hand position and not cursor position. (E,F), Mean velocity profiles across trial bins (20 trials per bin) and across all force field groups (E) and all rotation groups (F). Arrow indicates mean detected movement termination (minimum velocity after success event) for the last 20 trials. Note that in some trials, movement velocity did not decay to zero since there was no requirement to hold the target position upon reaching it. Only successful trials were included.
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Figure 2: Sequential adaptations to force fields and visuomotor rotations. Hand paths of representative subjects from each group following the A–B–A paradigm. The subplots are organized according to task (row) and direction of perturbations (column): double force field (A), matched force-rotation (B), opposite force field (C), non-matched force-rotation (D). Each subplot shows the average trajectories of early trials (trials 1–5, colored) and of late trials (trials 181–200, black) for tasks A and B performed on the first day-session and for retest on task A 24 h later. Hand paths, plotted from detected movement onset to movement end, show displacement from origin to a target at 90° (gray circle). Learned target direction was always at 90°. In (B), visuomotor rotation was counterclockwise and the required hand movement direction was towards a target at 45° (light gray circle) while in (D), rotation was clockwise and the required hand movement direction was towards a target at 135° (light gray circle). Note that trajectories correspond to hand position and not cursor position. (E,F), Mean velocity profiles across trial bins (20 trials per bin) and across all force field groups (E) and all rotation groups (F). Arrow indicates mean detected movement termination (minimum velocity after success event) for the last 20 trials. Note that in some trials, movement velocity did not decay to zero since there was no requirement to hold the target position upon reaching it. Only successful trials were included.

Mentions: Figures 2A–D illustrates the 2-by-2 design with task (row) and direction (column) effects on the hand trajectories of representative subjects from each group. Average trajectories are shown for tasks A and B performed on the first day-session and for retest on task A 24 h later. As previously shown in many studies and likewise observed here, trajectories were deviated in the direction of the force field or visuomotor rotation early in adaptation. With practice, directional deviations were progressively reduced and the trajectories recovered their straightness.


Discordant Tasks and Motor Adjustments Affect Interactions between Adaptations to Altered Kinematics and Dynamics.

Arce F, Novick I, Vaadia E - Front Hum Neurosci (2010)

Sequential adaptations to force fields and visuomotor rotations. Hand paths of representative subjects from each group following the A–B–A paradigm. The subplots are organized according to task (row) and direction of perturbations (column): double force field (A), matched force-rotation (B), opposite force field (C), non-matched force-rotation (D). Each subplot shows the average trajectories of early trials (trials 1–5, colored) and of late trials (trials 181–200, black) for tasks A and B performed on the first day-session and for retest on task A 24 h later. Hand paths, plotted from detected movement onset to movement end, show displacement from origin to a target at 90° (gray circle). Learned target direction was always at 90°. In (B), visuomotor rotation was counterclockwise and the required hand movement direction was towards a target at 45° (light gray circle) while in (D), rotation was clockwise and the required hand movement direction was towards a target at 135° (light gray circle). Note that trajectories correspond to hand position and not cursor position. (E,F), Mean velocity profiles across trial bins (20 trials per bin) and across all force field groups (E) and all rotation groups (F). Arrow indicates mean detected movement termination (minimum velocity after success event) for the last 20 trials. Note that in some trials, movement velocity did not decay to zero since there was no requirement to hold the target position upon reaching it. Only successful trials were included.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2806051&req=5

Figure 2: Sequential adaptations to force fields and visuomotor rotations. Hand paths of representative subjects from each group following the A–B–A paradigm. The subplots are organized according to task (row) and direction of perturbations (column): double force field (A), matched force-rotation (B), opposite force field (C), non-matched force-rotation (D). Each subplot shows the average trajectories of early trials (trials 1–5, colored) and of late trials (trials 181–200, black) for tasks A and B performed on the first day-session and for retest on task A 24 h later. Hand paths, plotted from detected movement onset to movement end, show displacement from origin to a target at 90° (gray circle). Learned target direction was always at 90°. In (B), visuomotor rotation was counterclockwise and the required hand movement direction was towards a target at 45° (light gray circle) while in (D), rotation was clockwise and the required hand movement direction was towards a target at 135° (light gray circle). Note that trajectories correspond to hand position and not cursor position. (E,F), Mean velocity profiles across trial bins (20 trials per bin) and across all force field groups (E) and all rotation groups (F). Arrow indicates mean detected movement termination (minimum velocity after success event) for the last 20 trials. Note that in some trials, movement velocity did not decay to zero since there was no requirement to hold the target position upon reaching it. Only successful trials were included.
Mentions: Figures 2A–D illustrates the 2-by-2 design with task (row) and direction (column) effects on the hand trajectories of representative subjects from each group. Average trajectories are shown for tasks A and B performed on the first day-session and for retest on task A 24 h later. As previously shown in many studies and likewise observed here, trajectories were deviated in the direction of the force field or visuomotor rotation early in adaptation. With practice, directional deviations were progressively reduced and the trajectories recovered their straightness.

Bottom Line: We found a gradient of interaction effects based on perturbation direction and task discordance.We also found that force field and visuomotor rotation had mutual anterograde and retrograde effects.Such overlap does not necessarily imply competition of resources.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Neurobiology, The Institute for Medical Research Israel-Canada, Hadassah Medical School, Hebrew University Jerusalem, Israel.

ABSTRACT
Motor control and adaptation are multi-determinate processes with complex interactions. This is reflected for example in the ambiguous nature of interactions during sequential adaptation of reaching under kinematics and dynamics perturbations. It has been suggested that perturbations based on the same kinematic parameter interfere. Others posited that opposing motor adjustments underlie interference. Here, we examined the influence of discordances in task and in motor adjustments on sequential adaptations to visuomotor rotation and viscous force field perturbations. These two factors - perturbation direction and task discordance - have been examined separately by previous studies, thus the inherent difficulty to identify the roots of interference. Forty-eight human subjects adapted sequentially to one or two types of perturbations, of matched or conflicting directions. We found a gradient of interaction effects based on perturbation direction and task discordance. Perturbations of matched directions showed facilitation while perturbations of opposite directions, which required opposing motor adjustments, interfered with each other. Further, interaction effects increased with greater task discordance. We also found that force field and visuomotor rotation had mutual anterograde and retrograde effects. However, we found independence between anterograde and retrograde interferences between similar tasks. The results suggest that the newly acquired internal models of kinematic and dynamic perturbations are not independent but they share common neuronal resources and interact between them. Such overlap does not necessarily imply competition of resources. Rather, our results point to an additional principle of sensorimotor adaptation allowing the system to tap or harness common features across diverse sensory inputs and task contexts whenever available.

No MeSH data available.


Related in: MedlinePlus