Anodal tDCS over the dorsolateral prefrontal cortex reduces Stroop errors. A comparison of different tasks and designs

In the present work, we evaluated the possibility to induce changes in the inhibitory control through noninvasive excitatory stimulation of the prefrontal cortex (PFC). To this aim, different montages of the transcranial direct current stimulation (tDCS) were adopted in three separate experiments, wherein different cognitive tasks were performed before and after the stimulation. In the first experiment, participants performed a visual Go/no-go task, and a bilateral anodic or sham stimulation was provided over the scalp area corresponding to the inferior frontal gyrus (IFG). In the second experiment, the IFG was stimulated unilaterally over the right hemisphere, and participants performed a Stroop task combined with a concurrent n-back task, which was aimed at overloading PFC activity. Since no behavioral effects of tDCS were observed in both experiments, we conducted a third experiment with different montage and paradigm. Stimulation was provided bilaterally over the dorsolateral PFC (DLPFC) in the context of a classic Stroop task: results indicated that anodal stimulation favored a reduction of errors. Present findings suggest that the bihemispheric stimulation of the DLPFC might be effective to increase inhibition in healthy subjects, and that this effect might be mediated by the implementation of sustained attention, as predicted by the attentional account of the inhibitory control.