Effects of transcranial magnetic stimulation and transcranial direct current stimulation on EEG alpha wave

Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are painless technique for nerve stimulation. It's possible to inhibit or excite neuron activity. For EEG alpha wave (8-14 Hz), it was affected to various brain activities. But, the most evident change was found when eyes closed and eyes opened. This study aims to investigate the effects of rTMS and tDCS on alpha wave during eyes closed and eyes opened. Both inhibited and excited conditions were applied on occipital area. EEGs were measured before and after stimulation for 1 minute of alternatively 10 seconds of eyes opening and 10 second of eyes closing. Subject follows these commands through wording on the monitor screen and beep sound form speaker. The alpha power between ±2 Hz of individual alpha frequency (IAF) was calculated during eyes closed and eyes opened in before and after stimulation. The results show that, the ratio of IAF alpha power (eyes closing/eyes opening) after 1 Hz rTMS and cathodal tDCS (inhibited condition) significant increase while tended to decrease after anodal tDCS (excited condition) compared with sham stimulation. These effects might cause from inhibited and excited active information processing in nerve cells that made alpha wave more synchronized and desynchronized. The alpha change according to stimulus point also related to originating area of alpha rhythm that generated in occipital area.