Online and offline effects of cerebellar transcranial direct current stimulation on motor learning in healthy older adults: a randomized double-blind sham-controlled study.

Abstract

The aim of this randomized double blinded sham-controlled study was to determine the effect of cerebellar anodal transcranial direct current stimulation (a-tDCS) on online and offline motor learning in healthy older individuals. Thirty participants were randomly assigned in experimental (n=15) or sham tDCS (n=15) groups. Participants in experimental group received 2mA cerebellar a-tDCS for 20min. However, the tDCS was turned off after 30seconds in sham group. Response time (RT) and error rate (ER) in serial RT test were assessed before, during 35minutes and 48h after the intervention. Reduction of RT and ER following the intervention session was considered as short-term (35min post intervention) and long-term offline learning (48h post intervention), respectively. Online RT and ER reduction were similar in both groups (P>0.05). RT was significantly reduced 48hours post intervention in cerebellar a-tDCS group (P=0.03). Moreover, RT was significantly increased after 35minutes and 48hours in sham tDCS group (P=0.03, P=0.007), which indicates a lack of short-term and long-term offline learning in older adults. A-tDCS on cerebellar region produced more short-term and long-term offline improvement in RT (P=0.014, P=0.01) compared to sham tDCS. In addition, online, short-term and long-term (48h) offline error reduced in cerebellar a-tDCS as compared to sham-control group, although this reduction was not significant (P>0.05). A deficit suggests that a direct comparison to a younger group was made. The findings suggested that cerebellar a-tDCS might be useful for improvement of offline motor learning in older individuals.