Significant <i>session x order</i> interaction.

<p>Individuals in the anodal—sham group (black, n = 7) exhibited larger performance improvements in the first than in the second session. By contrast, individuals in the sham—anodal group (gray, n = 7) exhibited smaller performance improvements in the first than in the second session. This finding lends further support to the observation that practice with anodal tDCS (solid bars) facilitated learning in comparison to sham tDCS (dotted bars). Data are shown as M ± SEM.</p

Anodal tDCS over the Primary Motor Cortex Facilitates Long-Term Memory Formation Reflecting Use-Dependent Plasticity

<div><p>Previous research suggests that anodal transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) modulates NMDA receptor dependent processes that mediate synaptic plasticity. Here we test this proposal by applying anodal versus sham tDCS while subjects practiced to flex the thumb as fast as possible (ballistic movements). Repetitive practice of this task has been shown to result in performance improvements that reflect use-dependent plasticity resulting from NMDA receptor mediated, long-term potentiation (LTP)-like processes. Using a double-blind within-subject cross-over design, subjects (n=14) participated either in an anodal or a sham tDCS session which were at least 3 months apart. Sham or anodal tDCS (1 mA) was applied for 20 min during motor practice and retention was tested 30 min, 24 hours and one week later. All subjects improved performance during each of the two sessions (p < 0.001) and learning gains were similar. Our main result is that long term retention performance (i.e. 1 week after practice) was significantly better when practice was performed with anodal tDCS than with sham tDCS (p < 0.001). This effect was large (Cohen’s d=1.01) and all but one subject followed the group trend. Our data strongly suggest that anodal tDCS facilitates long-term memory formation reflecting use-dependent plasticity. Our results support the notion that anodal tDCS facilitates synaptic plasticity mediated by an LTP-like mechanism, which is in accordance with previous research.</p></div

Stimulation effects.

<p>Performance improvements relative to the first training block for the anodal tDCS session (black squares) and the sham tDCS session (gray triangles). Training was performed while stimulation was applied (filled symbols), while retention tests at day 1 (RT-D1-1), day 2 (RT-D2-1…RT-D2-3) and 7 (RT-D7-1…RT-D7-3) were performed without stimulation (open symbols). * indicates blocks where LSD post hoc tests indicate significant differences of anodal tDCS versus sham stimulation (p < 0.001). Data are shown as M ± SEM.</p

Order effects.

<p>Peak velocity data of the practice blocks (train1…10) performed in session 1 (black squares) and session 2 (gray circles). Note that when data are collapsed across anodal tDCS and sham tDCS conditions peak velocity was generally higher in the second session, but the extent of improvement over the course of learning was similar. Data are shown as M ± SEM.</p

Individual subject data.

<p>Individual subject data showing gains/savings measured during the retention test at day 7 compared to performance at the end of training (i.e. average performance at RT-D7-1…3 minus average performance at train8…10). Individuals exhibiting the same trend as the group average are shown in black. Only one subject (gray) exhibited better retention performance after practice with sham tDCS than after practice with anodal tDCS.</p