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Movement speed is biased by prior experience.

Hammerbeck U, Yousif N, Greenwood R, Rothwell JC, Diedrichsen J - J. Neurophysiol. (2013)

Bottom Line: Reduced speed variability was also associated with reduced errors in movement amplitude for the fast training group, which generalized nearly fully to a new movement direction.In contrast, changes in perpendicular error were specific to the trained direction.In sum, our results suggest the existence of a relatively stable but modifiable prior of preferred movement speed that influences the choice of movement speed under a range of task constraints.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neurology, University College London, London, United Kingdom;

ABSTRACT
How does the motor system choose the speed for any given movement? Many current models assume a process that finds the optimal balance between the costs of moving fast and the rewards of achieving the goal. Here, we show that such models also need to take into account a prior representation of preferred movement speed, which can be changed by prolonged practice. In a time-constrained reaching task, human participants made 25-cm reaching movements within 300, 500, 700, or 900 ms. They were then trained for 3 days to execute the movement at either the slowest (900-ms) or fastest (300-ms) speed. When retested on the 4th day, movements executed under all four time constraints were biased toward the speed of the trained movement. In addition, trial-to-trial variation in speed of the trained movement was significantly reduced. These findings are indicative of a use-dependent mechanism that biases the selection of speed. Reduced speed variability was also associated with reduced errors in movement amplitude for the fast training group, which generalized nearly fully to a new movement direction. In contrast, changes in perpendicular error were specific to the trained direction. In sum, our results suggest the existence of a relatively stable but modifiable prior of preferred movement speed that influences the choice of movement speed under a range of task constraints.

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Transfer to target positioned 45° clockwise. A: change (pre/post) in maximum movement speed in the fast and slow training groups. B: change in endpoint error. C: perpendicular error. D: parallel error.
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Figure 8: Transfer to target positioned 45° clockwise. A: change (pre/post) in maximum movement speed in the fast and slow training groups. B: change in endpoint error. C: perpendicular error. D: parallel error.

Mentions: Finally, we assessed how training changed preferred speed and endpoint accuracy for movements aimed at a target that was 45° clockwise to the trained direction (Fig. 1B). Figure 8A shows that, compared with the baseline (pretraining) data, movements at all target speeds were slower in the slow training group and faster in the fast training group with a significant effect of TRAINING GROUP [F(1,16) = 11.391, P = 0.004]. The size of the effect was, however, smaller than for movements made in the trained direction (compare with Fig. 4C). Peak speed variability was also reduced in the new direction [significant effect of TIME, F(1,16) = 8.664, P = 0.010] but to a lesser degree than in the trained direction (Fig. 8B).


Movement speed is biased by prior experience.

Hammerbeck U, Yousif N, Greenwood R, Rothwell JC, Diedrichsen J - J. Neurophysiol. (2013)

Transfer to target positioned 45° clockwise. A: change (pre/post) in maximum movement speed in the fast and slow training groups. B: change in endpoint error. C: perpendicular error. D: parallel error.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4527989&req=5

Figure 8: Transfer to target positioned 45° clockwise. A: change (pre/post) in maximum movement speed in the fast and slow training groups. B: change in endpoint error. C: perpendicular error. D: parallel error.
Mentions: Finally, we assessed how training changed preferred speed and endpoint accuracy for movements aimed at a target that was 45° clockwise to the trained direction (Fig. 1B). Figure 8A shows that, compared with the baseline (pretraining) data, movements at all target speeds were slower in the slow training group and faster in the fast training group with a significant effect of TRAINING GROUP [F(1,16) = 11.391, P = 0.004]. The size of the effect was, however, smaller than for movements made in the trained direction (compare with Fig. 4C). Peak speed variability was also reduced in the new direction [significant effect of TIME, F(1,16) = 8.664, P = 0.010] but to a lesser degree than in the trained direction (Fig. 8B).

Bottom Line: Reduced speed variability was also associated with reduced errors in movement amplitude for the fast training group, which generalized nearly fully to a new movement direction.In contrast, changes in perpendicular error were specific to the trained direction.In sum, our results suggest the existence of a relatively stable but modifiable prior of preferred movement speed that influences the choice of movement speed under a range of task constraints.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neurology, University College London, London, United Kingdom;

ABSTRACT
How does the motor system choose the speed for any given movement? Many current models assume a process that finds the optimal balance between the costs of moving fast and the rewards of achieving the goal. Here, we show that such models also need to take into account a prior representation of preferred movement speed, which can be changed by prolonged practice. In a time-constrained reaching task, human participants made 25-cm reaching movements within 300, 500, 700, or 900 ms. They were then trained for 3 days to execute the movement at either the slowest (900-ms) or fastest (300-ms) speed. When retested on the 4th day, movements executed under all four time constraints were biased toward the speed of the trained movement. In addition, trial-to-trial variation in speed of the trained movement was significantly reduced. These findings are indicative of a use-dependent mechanism that biases the selection of speed. Reduced speed variability was also associated with reduced errors in movement amplitude for the fast training group, which generalized nearly fully to a new movement direction. In contrast, changes in perpendicular error were specific to the trained direction. In sum, our results suggest the existence of a relatively stable but modifiable prior of preferred movement speed that influences the choice of movement speed under a range of task constraints.

Show MeSH