Transcranial Direct Current Stimulation Enhances Motor Skill Learning but Not Generalization in Chronic Stroke.
Manuela Hamoudi, Heidi M Schambra, Brita Fritsch and 4 others
PMID 29683030WHAT IT FOUND
Adding real anodal tDCS to five days of pinch training raised the trained-task learning score (2.29 vs 1.53), but gave no extra gain on untrained hand tests.
Training alone improved those tests.
Key findings
01Total learning, the primary outcome, was greater with real tDCS than sham: 2.29±0.16 versus 1.53±0.25 unitless skill change (p=0.02, d=0.86).
02Training improved untrained hand tests, but real tDCS did not add to that effect: Grooved Pegboard accuracy and Jebsen Taylor speed differed by training state (p=0.038 and p=0.039), with no significant tDCS condition effect (p=0.757).
03For the trained pinch task, real tDCS mainly increased speed and smoothness, not accuracy: movement times were faster and smoothness greater than sham, while target error rates decreased similarly.
STILL TO COME
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What it does not show
Only 50 of 56 enrolled patients were analyzed after dropouts and exclusions. The study included only patients with mild to moderate hemiparesis and enough hand function to perform the pinch task, so it says little about more severely affected stroke patients. It was powered for total learning and learning stages across five days, not for effects on individual training days. The no-training/no-tDCS group was added during the experiment rather than being part of the original real-versus-sham randomization. Blinding was single-blind at the NIH site and double-blind only at the Freiburg site. The primary skill outcome was a unitless index from a computerized pinch task, not a standard clinical scale or ADL measure. The tDCS benefit was task-specific; untrained hand tests improved with training but showed no significant added tDCS effect.
Declared interests
The authors declared no conflict of interest. The article text does not state a funding source, although the publication types list NIH intramural support.
The easy way to misread this
Do not conclude that tDCS improves hand function after stroke. The real tDCS group learned the trained pinch task more than sham, but tDCS did not add to improvements on untrained hand tests; training alone produced those generalization gains.