Modulation of smoker brain activity and functional connectivity by tDCS: A go/no-go task-state fMRI study

BACKGROUND: Transcranial direct current stimulation (tDCS) applied to particular brain areas may reduce a smoker's smoking cravings. Most studies on tDCS mechanisms are performed on brains in the resting state. Therefore, brain activity changes induced by tDCS during tasks need to be further studied. METHODS: Forty-six male smokers were randomised to receive anodal tDCS of the left/right dorsolateral prefrontal cortex (DLPFC) or sham tDCS. A go/no-go task was performed before and after stimulation, respectively. Brain activity and functional connectivity (FC) changes during the task state before and after tDCS were used for comparison. RESULTS: This study revealed that the anodal stimulation over one DLPFC area caused decreased activity in the ipsilateral precuneus during the go task state. Right DLPFC stimulation increased the FC between the bilateral DLPFCs and the right anterior cingulate cortex (ACC), which is closely associated with cognition and inhibition of executive functions. Additionally, the study showed variations in brain activity depending on whether the anode was positioned over the right or left DLPFC (R-DLPFC or L-DLPFC). CONCLUSION: During the go task, tDCS might exert a suppressive effect on some brain areas, such as the precuneus. Stimulation on the R-DLPFC might strengthen the FC between the right ACC and the bilateral DLPFCs, which could enhance the ability of behavioural decision-making and inhibition to solve conflicts effectively. Stimulating the L-DLPFC alone could increase the FC of bilateral DLPFCs with some brain regions associated with response inhibition.