Initial performance modulates the effects of cathodal transcranial direct current stimulation (tDCS) over the right dorsolateral prefrontal cortex on inhibitory control

Transcranial direct current stimulation (tDCS) has received considerable attention as a new option to facilitate cognitive ability or rehabilitation in healthy populations or in individuals with neuropsychiatric disorders. However, the tDCS effect varies widely, possibly because individual differences in initial performance have frequently been ignored in previous research. Here, we aimed to examine the influence of initial performance on inhibitory control after tDCS. Fifty-six participants were randomly divided into three groups: anodal, cathodal and sham stimulation. The go/no-go task, stop-signal task and Stroop task were performed to measure inhibitory control before and immediately after tDCS. tDCS was applied to the F4 site (international 10-20 system), corresponding to the right dorsolateral prefrontal cortex (rDLPFC), for 20 min with an intensity of 1.5 mA. Neither anodal nor cathodal stimulation had significant effects on the performance of these three tasks at the group level in comparison with sham stimulation. However, the analyses at the individual level only showed a negative relationship between baseline performance and the magnitude of change in go/no-go task performance following cathodal tDCS, indicating the dependence of the change amount on initial performance, with greater gains (or losses) observed in individuals with poorer (or better) initial performance. Together, the initial performance modulates the proactive inhibitory effect of cathodal tDCS of the rDLPFC. Additionally, the rDLPFC plays a crucial role in proactive inhibition.