In this paper, we used transcranial Direct Current Stimulation (tDCS) to evaluate it’s effect on arithmetic performance as well as on the neural correltates in the EEG. Bruno Rütsche replicated our previous finding that tDCS improved performance in complex subtractions (Hauser et al., 2013). However, the same stimulation impaired performance in simple arithmetic fact retrieval. The stimulation effects were also accompagnied by changes in alpha / theta de- / synchronizations.
Rütsche B, Hauser TU, Jäncke L & Grabner RH (2015). When problem size matters: Differential effects of brain stimulation on arithmetic problem solving and neural oscillations. PLOS One.