The ERSP images of frontal cluster with five cases. (a) The ERSP images of frontal cluster with five cases. The right column show the onset sequences of the two tasks. Color bars indicate the magnitude of ERSPs. Red solid lines show the onset of the math task. Red dashed lines show the mean response time for the math task. Blue solid lines show the onset of the deviation task. Blue dashed lines show the mean response time for the deviation task. The red circle pointed out by the red arrow in case 2 means the red solid line and blue solid line are on the same position. Latencies calculated from (a) are shown in (b) by calculating time form the math task onset to the first occurrence of power increases. The open bars represent the latencies in the theta (4.5 ~ 9 Hz) band. The gray bars represent these latencies in the beta (11 ~ 15 Hz) band. The comparison of total power in cross-subject (14 subjects) averaged ERSP images in the frontal cluster between cases is shown in (c). The amount of total power is calculated by adding all the power increases in the same temporal period and the same frequency band. The open bars represent the total power in the theta band. The gray bars represent the total power in the beta band.