Distinct cortical areas for motor preparation and execution in human identified by Bereitschaftspotential recording and ECoG-EMG coherence analysis

Objective: To clarify the cortical areas involved in motor preparation and execution by investigating Bereitschaftspotentials (BPs) and electrocorticogram-electromyogram (ECoG-EMG) coherence from subdural electrodes placed around the rolandic area. Methods: BPs and ECoG-EMG coherence were investigated for presurgical evaluation in a patient with cavernoma in the left frontal lobe. BPs were recorded in association with the tongue, right hand and right foot movements. ECoG-EMG coherence was calculated in association with weak muscle contraction of the right hand. Results: Two cortical areas related to voluntary motor control were identified; one in the primary hand motor area, which generated surface-negative BPs with hand movements and showed significant coherence of ECoG with EMG of the contralateral hand muscle, and the other in the ventral rolandic area posterior to the central sulcus, which generated surface-positive BPs with voluntary movements of multiple sites (hand, tongue and foot) but did not show any ECoG-EMG coherence. Conclusions: It is postulated that the former area represents the primary motor area involved in both motor preparation and execution, and the latter area represents the non-primary motor area involved in motor preparation. Significance: BP recording combined with ECoG-EMG coherence analysis could reveal the functional roles of motor cortices and the reorganization induced by structural brain lesion.