Increased synchronization of cortical oscillatory activities between humansupplementary motor and primary sensorimotor areas during voluntary movements

In human, both primary and nonprimary motor areas are involved in the contr ol of voluntary movements. However, the dynamics of functional coupling amo ng different motor areas has not been fully clarified yet. Because it has b een proposed that the functional coupling among cortical areas might be ach ieved by the synchronization of oscillatory activity, we investigated the e lectrocorticographic coherence between the supplementary motor and primary sensorimotor areas (SMA and S1-M1) by means of event-related partial cohere nce analysis in 11 intractable epilepsy patients. We found premovement incr ease of coherence between the SMA proper and S1-M1 at the frequency of 0-33 Hz and between the pre-SMA and S1-M1 at 0-18 Hz. Coherence between the SMA proper and M1 started to increase 0.9 sec before the movement onset and pe aked 0.3 sec after the movement. There was no systematic difference within the SMA (SMA proper vs pre-SMA) or within the S1-M1, in terms of the time c ourse as well as the peak value of coherence. The phase spectra revealed ne ar-zero phase difference in 57% (20 of 35) of region pairs analyzed, and th e remaining pairs showed inconsistent results. This increase of synchroniza tion between multiple motor areas in the preparation and execution of volun tary movements may reflect the multiregional functional interactions in hum an motor behavior.