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. 2017 Sep 12;6:e26602. doi: 10.7554/eLife.26602

Figure 2. M1 a-tDCS during Prism Adaptation (PA) enhanced consolidation of the prism after-effect.

The x-axis represents baseline accuracy (zero error), with prism after-effect (AE) data representing changes from baseline. For each panel N = 9. Asterisk indicates significant difference between Anodal and Sham (p<0.05). (A) Pointing accuracy in healthy volunteers when anodal (red) or sham (blue) tDCS was applied to M1 during Adaptation (Experiment 1). Black wedges indicate blocks throughout which prisms were worn. During Adaptation (prism exposure, (E1–E6) and Washout (prisms removed, (W1–W6), participants saw the outcome of the trial, so could correct their errors. The AE was measured without visual feedback (AE1-15, shaded light grey). Solid lines show pointing accuracy averaged across participants (shading =±1 SEM). Adaptation and Washout lasted 20 min each. Retention lasted 6 min after 10 min of blindfolded rest. Relative to sham, anodal tDCS increased AE persistence throughout Washout and Retention: note the leftward shift in AE7-15 (no visual feedback), whereas accuracy in interleaved blocks W1-6 is indistinguishable. (B–E) Prism after-effect in different stimulation conditions. Panel (B) summarizes group mean AEs (±1 SEM) for the dataset shown in (A) (AE1-15 only) and also shows data for reversed polarity stimulation (cathodal, green). Other panels plot the same summary AE data for stimulation of: (C) M1 before Adaptation (Experiment 2); (D) right posterior parietal cortex (PPC) during Adaptation (Experiment 3); E) right cerebellum (CB) during Adaptation (Experiment 4).

Figure 2.

Figure 2—figure supplement 1. Control experiment 5: M1 a-tDCS alone does not cause a leftward shift in pointing behavior.

Figure 2—figure supplement 1.

Data are group mean open-loop pointing errors (±1 SEM; N = 10) for sham and anodal tDCS conditions in the identical behavioural protocol to that shown in Figure 2 (ie: Adaptation, Washout, Retention) except that sham (not prism) glasses were used (Experiment 5). There is no leftward shift in pointing behavior in either condition. This confirms that M1 a-tDCS alone does not induce the sustained leftward shift in pointing behavior shown in Figure 2A,B and Figure 3.