Increased left prefrontal brain perfusion after MRI compatible tDCS attenuates momentary ruminative self-referential thoughts

BACKGROUND Transcranial direct current stimulation (tDCS) is a non-invasive electrical stimulation technique, assumed to influence cognition and emotional processing. OBJECTIVE However, it is unclear how tDCS influences spontaneous cognitive processes such as momentary self-referential thoughts on the neuronal level. METHODS Forty healthy female volunteers participated in a single session sham-controlled crossover tDCS study while being in the MRI scanner. We measured brain perfusion (arterial spin labeling) just before and just after tDCS. Before and after the stimulation procedure, participants were scored on mood (visual analogue scales) and on the Momentary Ruminative Self-focus Inventory (MRSI). We performed a 1.5 mA, 20-min, anodal left dorsolateral prefrontal cortex, cathodal right supraorbital stimulation. RESULTS One sham-controlled tDCS session did not result in subjective mood changes. However, as compared to before, MRSI scores significantly decreased only after active tDCS. Regression analysis revealed that this reduction in momentary ruminative self-referential thoughts was related to tDCS-related increases in left prefrontal cortical perfusion. tDCS decreased momentary self-referential thoughts, which was associated with increasing perfusion in the left prefrontal cortex. CONCLUSION Our findings are in line with the hypothesis that tDCS of the DLPFC attenuates ruminative processes.