Despite reports of some side effects, tDCS is considered to be a safe technique [16]. The most common side effects are tingling and itching under the electrodes. Nausea, insomnia and headache are less frequently reported. It should be noted that these side effects have also been observed in sham conditions.

TMS solutions

Previously, intensity-dependent metabolic changes have been found with positron emission tomography and blood oxygen level dependent magnetic resonance imaging after TMS to motor/prefrontal cortex; bilateral motor/prefrontal and auditory activation is induced, which becomes stronger with increasing pulse intensity [Bohning et al.,1999,2000; Fox et al.,1997; Nahas et al.,2001; Siebner et al.,1999; Speer et al.,2003]. However, these results are not directly comparable with our EEG findings. Arising a few seconds poststimulus, metabolic changes reflect relatively long-lasting activity of interconnected neuronal networks, whereas we were interested in the TMS-evoked events that occurred within a fraction of a second.