Transcranial direct-current stimulation combined with attention increases cortical excitability and improves motor learning in healthy volunteers.

The sample was small, and the sample size was based on previous studies rather than a formal calculation of how many participants were needed. The study was not pre-registered. All participants were healthy right-handed adults, so the findings do not show effects in people with stroke or other clinical conditions. The motor task was a simple ballistic thumb movement, not a functional daily activity; the authors state it is unclear whether the results transfer to activities of daily living. Experiment 1 did not include a sham tDCS condition in the main three sessions, although a separate eight-participant sham experiment was done. Some follow-up data were missing because of a device issue: one participant at 1 day in the sham tDCS plus target attention group, two participants at 30 days in the anodal tDCS plus target attention group, three participants at 30 days in the sham tDCS plus target attention group, and three participants at 30 days in the anodal tDCS plus no attention group. The motor learning result does not fully separate the contributions of tDCS and attention, because sham tDCS with target attention also improved performance at 7 days.

Funding was from the Japan Society for the Promotion of Science.

Do not read this as evidence that brain stimulation improves patient rehabilitation. The study was in healthy right-handed adults, used a laboratory thumb task, and did not test people with stroke or other clinical conditions.