In older adults resting-state alpha power is associated with stronger effects of anodal tDCS over prefrontal cortex on dynamic balance

In the present research, we examined the effects of transcranial direct current stimulation (tDCS) on learning a dynamic balance task (DBT) in healthy older adults (OA). In a pre-and post-test randomized crossover design, eighteen healthy OA underwent DBT training while receiving tDCS either in two real stimulation conditions or a sham stimulation condition as control. We compared two target regions for anodal (a)-tDCS (primary motor cortex, M1/Cz, and dorsolateral prefrontal cortex, DLPFC/F3) and hypothesized that not only targeting M1 would be effective as previously shown for young adults but that, due to age-related deficiencies in cognitive control, enhancing cognitive resources through a-tDCS over left DLPFC would also facilitate dynamic balance training (DBT) in OA. Additionally, we explored changes in resting-state EEG oscillations and investigated whether practice effects could be predicted with resting-state EEG at baseline. Our results revealed that in the F3 condition, OA performed better than in the other two stimulation conditions (Cz, sham). Further, our results confirmed a negative transfer effect on untrained static balance tasks. Lower alpha power at baseline significantly predicted a stronger practice effect in the F3 condition. We conclude that the effects of tDCS on balance training and balance performance in OA depend on mental states at baseline as indicated by resting-state brain oscillations.