Comparison of Transcranial Direct Current Stimulation of the Primary Motor Cortex and Cerebellum on Static Balance in Older Adults

Background: Falling is a major problem in older adults. Transcranial direct current stimulation (tDCS) is a neuromodulation technique to improve balance in the elderly. The majority of previous studies have assessed the effects of cerebellar and primary motor cortex (M1) tDCS, while less attention has been paid to the comparison of the effects of tDCS in these two regions. Objectives: The goal of this study was to compare the effectiveness of cerebellum and M1 tDCS on the balance in older adults. Methods: In this double-blind sham-controlled crossover study, a total of 32 healthy older adults were randomly assigned to two groups of M1 and cerebellum tDCS. Each group received active and sham stimulation with a crossover design within a one-week interval. The intensity and duration of tDCS were 2 mA and 20 minutes, respectively. Before and after each session, the total path length (TPL) and mean velocity(MV) of the center of pressure were determined using a force plate in both mediolateral and anteroposterior directions under single-task and dual-task conditions. Results: The results of mixed ANOVA test showed that the main effect of time on TPL and MV was significant in both mediolateral (P < 0.01) and anteroposterior (P = 0.01) directions. The interaction between time and stimulation was also significant on TPL and MV in both mediolateral (P < 0.001) and anteroposterior (P < 0.001) directions. The between-group analysis showed no significant difference in the efficacy of cerebellar and M1 tDCS in the mediolateral (P = 0.79) and anteroposterior (P = 0.60) directions. Conclusions: Anodal tDCS of the cerebellum and Ml could improve the postural balance indices in healthy older adults. These two techniques exerted similar effects on static balance.