Figure 4.

An illustrative case of SMA mapping. (A) The schema of cortical mapping by MEPs. Subdural grid electrodes are placed on the right lateral frontoparietal and medial frontal cortices. Single pulse electrical stimulation reveals positive motor functions based on MEPs. In electrodes B08–09, a negative motor response is elicited by 5-train electrical stimulation. (B) CCEP waveforms (Plate B). Single-pulse electrical stimulation was applied to a pair of electrodes A08–09 (Plate A), which was defined as the primary motor area of the left hand. Two trials are plotted in superimposition. A large CCEP response was recorded in electrodes B06, B11-13, and B17. The functional brain region associated with those electrodes was confirmed as the SMA by MEP. (C) MEP waveforms (electrodes B06–07). MEP was elicited from the bilateral deltoid muscles, and the site of electrodes B06-07 was defined as the SMA. CCEP, cortico-cortical evoked potential; CS, central sulcus; DEL, deltoid muscle; L, left; MEP, motor evoked potential; R, right; SMA, supplementary motor area. Adapted with permission from Shibata et al. (2020) and Yamao et al. (2015).