Modulations of motor beta-band activity are better explained by changes in action utility rather than movement speed


Despite attempts to associate the amplitude of beta-band activity (13-30 Hz; ?) from motor regions with movement velocity, the existence of a linear association between the two is still debated. Alternatively, ? might reflect the action valuation process, which in turn influences movement velocity. Consequently, the objective of the present study was to dissociate movement velocity and utility and test their respective influence on ?. 31 right-handed participants performed a speed-controlled reaching task while EEG was recorded. The required velocity was indicated by a gauge, with maximal filling corresponding to participants' maximal velocity. Two different target positions were used, each associated with different maximal peak velocity. This difference was leveraged to define conditions with identical velocity requirements but different relative effort. Results showed a significant effect of the gauge's filling, but not of the presented target on ?. Furthermore, ? was significantly decreased both for high and low fillings as compared to a medium filling. Probability density functions revealed that the most chosen velocities were on average closer to the ones required at a medium filling. These preferences were used to model action utility as a function of peak velocity. Linear mixed effect modeling revealed that action utility, but not peak velocity, significantly predicted variations of ?. These results show that modulations of ? with movement velocity are better explained by changes in action utility rather than velocity. They bring up the intriguing perspective that manipulating ? may influence motor motivation and thus effort exertion.