Figure 2.

Grand-averaged time-frequency representations of total power of oscillatory activity (1-30 Hz) on (A) the anterior ROI and (B) the posterior ROI for both tasks. Stimuli were presented from 0 to 500 ms. Color bars indicate scales of the power (μV²). Note the alpha activity (about 10 Hz) on the posterior ROI (averaged across the electrodes Pz, O1, Oz and O2) and the theta activity (about 6 Hz) on the anterior ROI (averaged across the electrodes AFz, F3, Fz and F4), and compare the differences between the two tasks, particularly before stimulus onset.