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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

Adaptation and retention of force fields and visuomotor rotations. Day1 and day2 time courses, showing trial-by-trial means and ±1 SEM of initial directional deviations for the following groups: double force field (A), matched force-rotation (B), opposite force field (C), and non-matched force-rotation (D), matched rotation-force (E), and opposite rotation (F). Shown are the first 80 trials and last 40 trials. The directional deviations of pre-learning standard trials (P) are also shown.
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Figure 6: Adaptation and retention of force fields and visuomotor rotations. Day1 and day2 time courses, showing trial-by-trial means and ±1 SEM of initial directional deviations for the following groups: double force field (A), matched force-rotation (B), opposite force field (C), and non-matched force-rotation (D), matched rotation-force (E), and opposite rotation (F). Shown are the first 80 trials and last 40 trials. The directional deviations of pre-learning standard trials (P) are also shown.

Mentions: In this section, we evaluated how the consolidation of motor memories differed depending on the nature of the intervening task. We first examined performance savings from day1 to day2 for each force field group. Figure 6 shows the time course of reduction in the directional deviations from day1 to day2. Savings were apparent as the directional deviations were significantly lower on day2 compared to day1 for all groups (Figures 6A–C, ANOVA phase effects: p < 0.0001) except for the non-matched force-rotation that exhibited interference (Figure 6D, p > 0.10). Moreover, we found a significant effect of perturbation directions (ANOVA effect of perturbation direction, F(1,20) = 6.6, p = 0.019). Indeed, perturbations of matched direction showed better IMPs over non-matched directions (Figure 5B, ANOVA p < 0.00001). Direction-matched force-rotation showed higher IMPs than double force fields, although it did not reach significance levels (Figure 5B compare mF vs. mFR (1), post-hoc, p > 0.10). Facilitation by a different task was apparent in that the IMPs were significantly higher than the controls (Figure 5B CF vs. mFR (2), post-hoc, p < 0.01) but not when tasks were similar (Figure 5B CF vs. mF (3), post-hoc, p > 0.10). Performance savings were similarly found in all rotation groups (Figures 6E,F, ANOVA p < 0.0001). While retention of force field was facilitated by intervening visuomotor rotation, retention of rotation learning with force field learning was not different from the retention in control rotation; mean IMPs were not significantly different between the matched rotation-force and control rotation groups (Figure 5B CR vs. mRF (4), post-hoc, p > 0.10). The difference may stem from differences in the tasks’ requirement for stabilization (Robertson et al., 2004).


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

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

Adaptation and retention of force fields and visuomotor rotations. Day1 and day2 time courses, showing trial-by-trial means and ±1 SEM of initial directional deviations for the following groups: double force field (A), matched force-rotation (B), opposite force field (C), and non-matched force-rotation (D), matched rotation-force (E), and opposite rotation (F). Shown are the first 80 trials and last 40 trials. The directional deviations of pre-learning standard trials (P) are also shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Adaptation and retention of force fields and visuomotor rotations. Day1 and day2 time courses, showing trial-by-trial means and ±1 SEM of initial directional deviations for the following groups: double force field (A), matched force-rotation (B), opposite force field (C), and non-matched force-rotation (D), matched rotation-force (E), and opposite rotation (F). Shown are the first 80 trials and last 40 trials. The directional deviations of pre-learning standard trials (P) are also shown.
Mentions: In this section, we evaluated how the consolidation of motor memories differed depending on the nature of the intervening task. We first examined performance savings from day1 to day2 for each force field group. Figure 6 shows the time course of reduction in the directional deviations from day1 to day2. Savings were apparent as the directional deviations were significantly lower on day2 compared to day1 for all groups (Figures 6A–C, ANOVA phase effects: p < 0.0001) except for the non-matched force-rotation that exhibited interference (Figure 6D, p > 0.10). Moreover, we found a significant effect of perturbation directions (ANOVA effect of perturbation direction, F(1,20) = 6.6, p = 0.019). Indeed, perturbations of matched direction showed better IMPs over non-matched directions (Figure 5B, ANOVA p < 0.00001). Direction-matched force-rotation showed higher IMPs than double force fields, although it did not reach significance levels (Figure 5B compare mF vs. mFR (1), post-hoc, p > 0.10). Facilitation by a different task was apparent in that the IMPs were significantly higher than the controls (Figure 5B CF vs. mFR (2), post-hoc, p < 0.01) but not when tasks were similar (Figure 5B CF vs. mF (3), post-hoc, p > 0.10). Performance savings were similarly found in all rotation groups (Figures 6E,F, ANOVA p < 0.0001). While retention of force field was facilitated by intervening visuomotor rotation, retention of rotation learning with force field learning was not different from the retention in control rotation; mean IMPs were not significantly different between the matched rotation-force and control rotation groups (Figure 5B CR vs. mRF (4), post-hoc, p > 0.10). The difference may stem from differences in the tasks’ requirement for stabilization (Robertson et al., 2004).

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