Citation

Reppert TR, Rigas I, Herzfeld D, Sedaghat-Nejad E, Komogortsev O, Shadmehr R. J. Neurophysiol. 2018; 120(2): 741-757.

Affiliation

Biomedical Engineering, Johns Hopkins University, United States.

Copyright

(Copyright © 2018, American Physiological Society)

DOI

10.1152/jn.00033.2018

PMID

29766769

Abstract

A common aspect of individuality is our subjective preferences in evaluation of reward and effort. The neural circuits that evaluate these commodities influence circuits that control our movements, raising the possibility that vigor differences between individuals may also be a trait of individuality, reflecting a willingness to expend effort. In contrast, classic theories in motor-control suggest that vigor differences reflect a speed-accuracy trade-off, predicting that those who move fast are sacrificing accuracy for speed. Here we tested these contrasting hypotheses. We measured motion of the eyes, head, and arm in healthy humans during various elementary movements (saccades, head-free gaze shifts, and reaching). For each person we characterized their vigor, i.e., the speed with which they moved a body part (peak velocity) with respect to the population mean. Some moved with low vigor, while others moved with high vigor. Those with high vigor tended to react sooner to a visual stimulus, moving both their eyes and arm with a shorter reaction-time. Arm and head vigor were tightly linked: individuals who moved their head with high vigor also moved their arm with high vigor. However, eye vigor did not correspond strongly with arm or head vigor. In all modalities, vigor had no impact on endpoint accuracy, demonstrating that differences in vigor were not due to a speed-accuracy tradeoff. Our results suggest that movement vigor may be a trait of individuality, not reflecting a willingness to accept inaccuracy, but demonstrating a propensity to expend effort.

Language: en

Keywords

basal ganglia; effort; movement vigor; reward; speed-accuracy tradeoff