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Effects of anodal transcranial direct current stimulation over the right posterior parietal cortex on Simon task and
Sho Kojima1, Kako Tanabe2, Mitsuki Todoroki3
1Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan; Graduate School of Health and Welfare, Niigata University of Health and Welfare, Japan; Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan.
Introduction:
Stimulus-response compatibility (SRC) tasks test cognitive judgment by requiring discrimination between relevant and irrelevant information. This study explored the effects of anodal transcranial direct current stimulation (tDCS) over the posterior parietal cortex (PPC) on performance in the Simon and Flanker tasks.
Methods:
Fifteen healthy, right-handed adults (age: 21.3 ± 0.6 years) participated in the study, completing the Simon and Flanker tasks before and after active and sham tDCS conditions in a crossover design. Sessions were randomized with a 5-day interval between them. Anodal tDCS (1 mA) was applied to the right PPC for 15 min, with sham stimulation lasting 30 s. Task performance was evaluated based on reaction time and accuracy pre- and post-stimulation. Statistical analyses were conducted using nonparametric tests.
Results:
For congruent Simon task trials, reaction times significantly decreased post-intervention for active and sham tDCS, with no change for incongruent trials. The SRC effect significantly decreased following active tDCS but remained unchanged with sham stimulation. For the Flanker task, no significant differences in SRC effects were observed pre- and post-intervention.
Conclusions:
Anodal tDCS over the right PPC improved Simon task performance by reducing the SRC effect. No significant changes were observed in the Flanker task, suggesting that the PPC's role in interference control may be specific to spatial compatibility effects, as seen in the Simon task.
