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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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Illustration of each participant's preferred movement speed at the 4 set movement times (in milliseconds).
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Figure 2: Illustration of each participant's preferred movement speed at the 4 set movement times (in milliseconds).

Mentions: The constraint on movement speed we imposed for the four different target speeds was asymmetric as can be observed (Fig. 2) by the limited spread of data at the fastest speed and much greater variance at low target speeds. The choice of target speed differed, however, between subjects, and this choice was relatively stable, demonstrated by the subject-by-subject correlation between the slowest target speed and the other slow target-speed conditions [900–700, r(16) = 0.894, P < 0.001; 900–500, r(16) = 0.868, P < 0.001]. Because the constraint of moving very fast in the 300-ms condition prevents a true choice of speed, we observe that the effect of the prior is abolished [900–300, r(16) = 0.261, P = 0.295].


Movement speed is biased by prior experience.

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

Illustration of each participant's preferred movement speed at the 4 set movement times (in milliseconds).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Illustration of each participant's preferred movement speed at the 4 set movement times (in milliseconds).
Mentions: The constraint on movement speed we imposed for the four different target speeds was asymmetric as can be observed (Fig. 2) by the limited spread of data at the fastest speed and much greater variance at low target speeds. The choice of target speed differed, however, between subjects, and this choice was relatively stable, demonstrated by the subject-by-subject correlation between the slowest target speed and the other slow target-speed conditions [900–700, r(16) = 0.894, P < 0.001; 900–500, r(16) = 0.868, P < 0.001]. Because the constraint of moving very fast in the 300-ms condition prevents a true choice of speed, we observe that the effect of the prior is abolished [900–300, r(16) = 0.261, P = 0.295].

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