Dual-tDCS over the right prefrontal cortex does not modulate stop-signal task performance

Stopping an already initiated action is crucial for human everyday behavior and empirical evidence points toward the prefrontal cortex playing a key role in response inhibition. Two regions that have been consistently implicated in response inhibition are the right inferior frontal gyrus (IFG) and the more superior region of the dorsolateral prefrontal cortex (DLPFC). The present study targets both regions with non-invasive brain stimulation to investigate their role in response inhibition. Thus dual-prefrontal transcranial direct current stimulation (tDCS) was applied to both IFG and DLPFC in a repeated measures design and compared to sham tDCS. Specifically, 9 cm2 electrodes were positioned over both IFG and DLPFC in all groups. The active stimulation groups received off-line, anodal or cathodal tDCS over the IFG and opposite polarity tDCS of the DLPFC, while the sham stimulation group received short stimulation at the start, middle and end of the supposed 20-min stimulation period. Before and after tDCS, subjects' inhibition capabilities were probed using the stop-signal task (SST). In a final sample of N = 45, participants were randomly split into three groups and received three different stimulation protocols. Results indicated that dual-frontal tDCS did not influence performance as compared to sham stimulation. This null result was confirmed using Bayesian analysis. This result is discussed against the background of the limitations of the present study as well as the potential theoretical implications