Optimizing cognitive control through the interaction between stimulation intensity and duration in single-site and dual-site tDCS

In the present study, we investigated the relationship between tDCS dosage and the effects of single-site and dual-site tDCS. In Experiment 1, two types of stimulation intensities (1 mA or 1.5 mA) were applied while participants performed a Flanker task. In Experiment 2, two different stimulation durations were manipulated while participants conducted the same task. Behavioural performance under different dosages was evaluated in the framework of both traditional reaction time measures and the drift diffusion model (DDM), respectively. Conventional reaction time analyses did not reveal any significant effect of stimulation intensity and stimulation duration on cognitive control task. In contrast, DDM analyses revealed that the detrimental effects of high-intensity tDCS diminished as tDCS continued. Additionally, these results showed that high-intensity tDCS in the single-site condition led to longer non-decision time, indicating an interruption to the perceptual and motor processes, while for dual-site tDCS, both the perceptual process and evidence accumulation process were interrupted with longer non-decision time and slower drift rates. This study underscores the importance of understanding the effects of tDCS from a temporal perspective, providing important implications for optimizing tDCS parameters and understanding the underlying mechanisms of using tDCS to enhance cognitive control.