As shown in Fig. 2(b), the position of each channel was numbered from 1 to 48. In order to cover the bilateral motor cortex and motor association cortex, the probes were placed symmetrically beside Cz since C3 and C4 were enclosed by channel numbers 16, 19, 20, and 23 and numbers 40, 43, 44, and 47, respectively. Consequently, Fz was placed essentially between channel numbers 4 and 28 in all subjects. In order to confirm the precise positions of the probes, we demonstrated a probe-cortex correlation using an appropriate software system (EZT-DM 101/102; Hitachi Medical Corporation, Japan). In this system, the spatial information of each probe on the head surface was first registered. Second, the 3-D head surface image and the 3-D brain image were generated from the subject’s own T1-weighted MRI data (MAGNETOM Verio 3T, Siemens, Germany), using 3-D reconstruction software (ZedView, LEXI, Tokyo, Japan), and each probe position was mapped onto the 3-D head surface image. Finally, probe positions were superimposed onto the subject’s own 3-D brain image [Fig. 2(c)]. In the present study, this procedure was performed in all subjects, and we obtained accurate regional information about hemodynamic responses to neural activation. Figure 2(c) shows that the bilateral prefrontal cortex (PFC), the bilateral dorsal premotor cortex (dPMC), and the bilateral hand area of the SMC were covered by the placement of the probes. According to the results of these processes, the regions of interest (ROIs) were set in all subjects for PFC (channels 4, 5, 28, and 29), dPMC (channels 11, 12, 35, and 36), and the hand area of SMC (channels 16, 19, 20, 23, 40, 43, 44, and 47) within an acceptable structural error range due to variable head or brain shape, as shown in Fig. 2(b).