Magnitude of the post-movement beta synchronization correlates with the variability of the ankle torque production

Abstract

Objectives During and after the completion of a motor task, an event-related desynchronization (ERD) and synchronization (ERS) – i.e., a decrease and increase of the 13–31 Hz spectral magnitude–are respectively recorded over the motor cortex (M1). The ERD is supposed to reflect M1 involvement to perform the motor task [1] , [2] while the ERS is supposed to reflect an active “top-down” cortical inhibition of the motor command [1] , [3] . Studies revealed that ERD/S are modulated with the force level [1] . However, it remains to know whether ERD/S are related to the task performance, reflecting force control. We investigated the relationship between the ERD/S and the accuracy and variability of the force production. Methods Eleven healthy participants performed 50 × 10-s isometric right plantar flexion contractions at 20% of their maximal torque. The ankle torque and the M1 EEG activity were recorded. After appropriate preprocessing, the absolute and variable errors (AE/VE) of the ankle torque, respectively reflecting accuracy and variability of the motor task and the ERD were computed during the holding force phase. The ERS was computed 1-s after the end of the contraction. All data were normally distributed. Pearson correlations between ERD/S and AE/VE were computed. Results No significant correlation was found between the ERD and VE (r2 = 0.11; P = 0.75) nor between the ERD and AE (r2 = 0.56; P = 0.07). The ERS significantly increased as the VE increased (r2 = 0.8; P Conclusion These results suggest that the ERD is not linked with fine motor control modulating accuracy and variability of force. However, the significant ERS-VE relationship suggests that the more variable is the force produced, the more M1 is deactivated, probably reflecting an increased inhibition of the motor command.