In this tDCS study the investigator uses one anode and one cathode electrode placed over the scalp to modulate a particular area of the central nervous system (CNS). The stimulation is administered via the neuroConn DC.Stimulator. The DC-STIMULATOR is a micro-processor-controlled constant current source. The DCSTIMULATOR is a CE-certified medical device for conducting non-invasive transcranial direct current stimulation (tDCS) on people.Electrode positioning is determined according to the International EEG 10-20 System.