Cortical networks underlying coordinated movements revealed by magnetoencephalographic beamforming

Event-related beamformer analyses was applied to magnetoencephalographic data from five subjects who performed synchronized and syncopated unimanual motor coordination tasks at rates ranging from 1.25 to 1.75 Hz. For syncopation, the stability of the coordination pattern decreased systematically with increasing movement rate. Averaged sensor data revealed the motor field (MF) and motor evoked fields (MEF) I and II. Additionally, we observed an early field (M0) at approximately 160 ms prior to peak flexion with polarity opposite to the MF. Beamformer analysis reproduced previous findings that showed the MF activity being generated mainly in precentral gyrus and the activity of the MEFs is distributed across multiple generators in pre- and post-central gyrus. For syncopation, additional areas of activation were observed during early M0 and late MEF II time periods which included premotor, frontal, cingulate, and SMA, with the premotor areas exhibiting a dependence on rate. These results provide evidence of the power of MEG beamforming for characterizing the properties of cortical neural activity at a high resolution in space and time.