High-beta bursts in SMA mediate anticipatory muscle inhibition in a bimanual motor task
Résumé
Abstract In motor networks, motor inhibition can be driven by sensorimotor mu rhythm (8-12Hz) or beta bursts (13-30Hz). In this study, we aimed to investigate whether mu or beta activity supports efficient anticipatory inhibition, as reflected by a decrease in electromyographic (EMG) activity. To test this, we recorded magnetoencephalography (MEG) in 16 adults performing a Bimanual Load Lifting Task (BLLT), where participants lifted a load with one hand supported by the other. In anticipation of unloading, elbow flexors in the supporting arm are inhibited to prevent elbow deflection. We observed that optimal postural stabilization occurs when flexor inhibition happens approximately 30 ms before unloading begins. Stronger EMG inhibition in this time interval correlated negatively with high-gamma power (90-130Hz), reflecting reduced neural excitability, and positively with high-beta power in the medial supplementary motor area (SMA). In contrast, no significant correlation was observed in the mu-range (8-12 Hz). Meanwhile, high-beta and high-gamma power were negatively correlated. Mediation analysis confirmed that gamma power significantly mediates the relationship between beta power and EMG inhibition. Beta burst probability and directed connectivity analysis using the Phase Slope Index indicated that high-beta bursts are transmitted from the middle prefrontal cortex (mPFC) and elbow-related primary motor cortex (M1) to the SMA. Our findings suggest that, in the voluntary unloading task, anticipatory muscle inhibition at the optimal time is driven by a reduction in excitability within the SMA, likely facilitated by high-beta bursts originating from the mPFC-M1-SMA network. Significance Anticipatory motor processes represent a form of higher-order motor control evolved in humans to enable precise hand manipulation. In this study, we used a bimanual coordination task where precise force control is achieved by sending an inhibitory motor command to the elbow flexors before an anticipated forearm disturbance, which requires accurate timing and pattern selection. We demonstrate that timely anticipatory inhibition is associated with the transmission of high-beta bursts (22-28Hz) to the supplementary motor area, suppression of which enables precise inhibitory control over the flexor muscle. These findings suggest the neural mechanisms underlying anticipatory postural control and provide the first direct evidence linking beta activity to muscle inhibition.
Domaines
Sciences du Vivant [q-bio]
Fichier principal
Manyukhina2025_HighBetaBurstsInSMAMediateAnticipatoryMuscleInhibitionInABimanualMotorTask.pdf (1)
Télécharger le fichier
Origine | Fichiers produits par l'(les) auteur(s) |
---|