| dc.description.abstract | Question: Accumulating evidence points towards the beneficial effects of tDCS on working memory (WM). Still, the reproducibility of increased WM performance following single session anodal tDCS
has been brought into question by some recent studies. In a series of experiments, we aimed to explore the effect of single-session anodal tDCS over both left and right dorsolateral prefrontal cortex (DLPFC) and posterior parietal cortex (PPC) on WM assessed by the n-back task (i.e., 3-back) in the verbal and non-verbal modality in the online and offline protocol.
Methods: Three sham-controlled within-subject design experiments were conducted. Each experiment had three conditions (anodal tDCS over DLPFC; anodal tDCS over PPC; and sham) that were repeated across participants in counterbalanced order (Exp1: N = 21, age range: 21–35 years, gender M/F = 9/12; Exp2: N = 21, age range: 20–35 years, gender M/F = 9/12; Exp3: N = 21, age range: 21–30, gender M/F = 10/11). In Exp1, participants completed verbal and non-verbal 3-back task immediately following 20 min tDCS over the left DLPFC/PPC (i.e., F3 and P3 of the International 10–20 EEG system). Exp2 followed the same protocol but with right-hemisphere electrode placement (i.e., F4 and P4 of the International 10–20 EEG system). Finally, in Exp3, the electrode placement was the same as in Exp1, but 3-back tasks were performed during instead of after the stimulation.
Results: The experiments yield mixed results. Namely, WM performance was enhanced following the stimulation of the right but not left DLPFC (p < .05). Furthermore, tDCS over right PPC positively affected performance on verbal (p < .05) but not non-verbal 3-back task (p = .15), while the stimulation of the left PPC enhanced nonverbal (p = .01), but not verbal 3-back task performance (p = .14). Finally, tDCS had no effect on neither verbal nor non-verbal 3-back
task in the online protocol (Exp3).
Conclusion: The results have shown that a single session of anodal tDCS can increase WM performance in young, healthy participants immediately following the stimulation. Still, it seems that the magnitude and the reproducibility of the effects depend on factors related to electrode positioning, i.e., stimulation site (frontal vs. parietal region; left/right hemisphere), experimental protocol (online/offline), as well as properties of the behavioral task (verbal/non-verbal material). | sr |
