Citation

Hammerbeck U, Yousif N, Greenwood RJ, Rothwell JC, Diedrichsen J. J. Neurophysiol. 2014; 111(1): 128-134.

Affiliation

University College London.

Copyright

(Copyright © 2014, American Physiological Society)

DOI

10.1152/jn.00522.2013

PMID

24133220

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 25cm-reaching movements within 300, 500, 700 or 900ms. They were then trained for 3 days to execute the movement at either the slowest (900ms) or fastest (300ms) speed. When retested on the fourth day, movements executed under all four time constraints were biased towards 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.

Language: en