Background Transcranial direct current stimulation (tDCS), which involves passing a gentle electrical current across the skull, could enhance brain function. When combined with a cognitive task, tDCS has been shown to improve targeted cognitive skills in patients with stroke and Parkinson’s disease. Huntington’s disease (HD) is associated with cognitive decline including impairments in working memory.
Aims We investigated the potential utility of tDCS for improving working memory in patients with HD, and which clinical and cognitive factors may predict efficacy.
Methods We conducted a double-blind, sham-controlled, within-participants trial of tDCS plus cognitive training in twenty patients with HD. Participants underwent both 1500 mA anodal tDCS over left dorsolateral prefrontal cortex and sham stimulation. The n-back task was used as an online cognitive training task, and required participants to watch a series of letters presented one-by-one, and indicate when the current letter was the same as the letter presented either 1 or 2 stimuli before. All subjects completed baseline clinical and cognitive assessment. Pre and post-tests included a digit recall and re-ordering test, a Stroop task (for comparison), and computerised n-back tests.
Results Performance differences from pre to post-test indicated a significant improvement in patients’ working memory span (increase of approximately half a point or 10%), but no significant difference for sham. There was a positive correlation between motor symptom ratings and gains in working memory span for tDCS, but not for sham. Patients with poorer baseline category fluency scores also showed greater improvement in working memory after tDCS. Stroop performance did not show a specific effect for tDCS.
Conclusions Dorsolateral prefrontal tDCS appears well tolerated in HD and could enhance working memory span. Motor symptoms and verbal fluency scores may help identify patients who are most likely to benefit from this intervention.
- transcranial direct current stimulation
- working memory