Bilateral frontal transcranial direct current stimulation: Failure to replicate classic findings in healthy subjects

Objective: There has been no modern effort to replicate, further characterize, or quantify the dramatic effects on affect described in controlled studies from the 1960s using bilateral frontal electrodes with an extra-cephalic reference in a mixed group composed primarily of mildly depressed individuals. We performed a comprehensive, quantitative assessment of the effects of bifrontal TDCS on emotion in 21 healthy subjects. Methods: In a double-blind crossover study, we administered tests of emotional state, affect, emotional decision-making, arousal, and psychomotor functions during sham, anodal, and cathodal TDCS. Results: We found no systematic effects on any measure, despite two subjects who had pronounced mood effects in the predicted direction. There were no adverse events. Conclusions: In line with some other studies, we found no consistent effects of bifrontal TDCS on measures of emotional function of psychomotor performance. Significance: These results demonstrate the safety of bilateral anterior frontal TDCS with an extra-cephalic reference, but raise questions about its effectiveness as a modulator of mood and emotional cognition, at least in healthy subjects.