Increased functional and directed corticomuscular connectivity after dynamic motor practice but not isometric motor practice.

Abstract

How do differences in the constraints of a practiced motor task affect oscillatory functional connectivity between the motor cortex and muscle? Here, we investigate corticomuscular (CM) and intermuscular (IM) coherence during the hold-phase of a dynamic position control (PC) and isometric force control (FC) task. We also investigate the effects of PC motor practice requiring precise wrist flexions to designated target positions, and effects of FC motor practice involving isometric wrist flexions to designated target force levels or rest in a control group. In 46 young healthy adults (aged 20-30 yr), full-cap electroencephalography (EEG) and electromyography (EMG) were recorded from the flexor and extensor carpi radialis muscles during the tasks. Beta-band (15-35 Hz) CM and IM coherence were investigated as a task-related marker of oscillatory activity in the corticospinal system. At baseline, higher CM coupling was demonstrated during position control compared with force control. Following PC motor practice, CM β-band coherence increased (P = 0.038), whereas it remained unchanged for participants who practiced FC or rested. This pattern was also found for IM coherence. The increased oscillatory synchronization following PC practice was driven by greater descending signaling (P = 0.025). We speculate that the observed differences between position and force control relate to task differences in corticomuscular control-strategy and the influence of different sensory modalities during motor practice. We interpret the results as indicating increased coupling between the motor cortex and the motoneuron pool of the contracting muscle following dynamic motor practice emphasizing requirements for position control in motor learning.NEW & NOTEWORTHY We present the effects of different types of motor practice on functional connectivity in the corticomuscular system. We present differences in corticomuscular connectivity between tasks with position versus force control emphasis and evidence for increased functional and directed connectivity within the network specifically following position-control motor practice. These findings support using different control strategies based on task constraints and emphasize the importance of dynamic motor practice focused on position control for increasing coherence.