Fig. 6
a Mean error distances between the motor hotspot locations identified by TMS-induced MEP and our EEG-based machine learning approach with respect to the number of channels (RM-ANOVA with Bonferroni corrected p-value < 0.05: Ch_Set5 > Ch_Set4 > Ch_Set3 = Ch_Set2 > Ch_Set1 for the right hand and Ch_Set5 > Ch_Set4 = Ch_Set3 > Ch_Set2 > Ch_Set1 for the left hand). The numbers below the bar graphs represent the mean error distances of each channel set and their standard errors denoted by error bars. The standard deviations of the mean error distances are ± 0.20 for Ch_Set1, ± 0.33 for Ch_Set2, ± 0.54 for Ch_Set3, ± 0.69 for Ch_Set4, ± 1.14 for Ch_Set5, respectively. No significant difference was observed between the left and right hand for all channel sets in terms of the error distance (paired t-test p > 0.05), except Ch_Set3 (left hand > right hand). The abbreviation, n.s., means no significant difference. b A representative example showing the 3D locations of the motor hotspots identified by TMS (blue rectangle) and the EEG-based approach with respect to the number of channels. The X, Y, and Z coordinates correspond to the left/right, posterior/anterior, and ventral/dorsal dimension, respectively, based on the Cz (origin: 0, 0, 0)