Task design and experimental setup. Experimental session: the subject performs 4 runs of 18 trials before stimulation, undergoes 20 minutes of stimulation and BCI trials, performs 4 runs after stimulation, performs a 13 minute visual oddball experiment with right hand response, and performs 4 runs delayed after stimulation (upper left). Setup of HD-tDCS electrodes (black circles) embedded within the 64 channel EEG cap (upper right). Single trial sequence of events: after the target is presented for 3 seconds, a red ball appears on the screen and moves based on the SMR control signal for a maximum of 6 seconds, and followed by a 3 second inter-trial interval (lower panel).