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

Abstract

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.

Keywords: Addiction; Behaviour control; Functional connectivity; Functional neuroimaging; Nicotine dependence; Seed-based analysis; Transcranial direct current stimulation.

Fig. 1

The experimental design of this study a. The experiment flow diagram (G_1,2: Go/No Go task). b. Schematic of the Go/No Go task operation.

Fig. 2

Brain MRI characteristics a. LEFT group (corrected p < 0.05); The region where the BOLD signal decreases were left middle occipital gyrus, left precuneus, and left crus I of the cerebellar hemisphere; b. RIGHT group (corrected p < 0.05); The region where the BOLD signal decreases were the right precuneus and left middle occipital gyrus. c. Comparison of LEFT group and SHAM group after stimulation; The region where the BOLD signal decreases were right thalamus, right lingual gyru, left lobule IV, V of cerebellar hemisphere and left crus I of the cerebellar hemisphere (corrected p < 0.05); The region where the BOLD signal increases were right parahippocampal gyrus and left middle occipital gyrus (corrected p < 0.001); d. Comparison of RIGHT group and SHAM group after stimulation; The region where the BOLD signal decreases were left superior temporal gyrus, right lobule III of cerebellar hemisphere (corrected p < 0.001).

Fig. 3

Go RT or No-Go error rate. a. Within group comparison of RT. b. Within group comparison of error rate (For each group, p＞0.05). Error bars indicates 95 % confidence interval. RT: reaction time; tDCS: Transcranial direct current stimulation.