Different roles of the monkey dorsolateral prefrontal, premotor and posterior parietal cortices in a delayed response task revealed by functional disturbance by on-line rTMS

s / Brain Stimulation 8 (2015) 310e325 321 alteration in the intensity of stimulation delivered to the brain. Elimination of this source of variability will facilitate replication and interpretation of tDCS findings. Furthermore, measurement and statistically accounting for drift may prove important for better characterizing the effects of tDCS on the human brain and behavior.