Preconditioning tDCS facilitates subsequent tDCS effect on skill acquisition in older adults

Functional motor declines that often occur with advancing age-including reduced efficacy to learn new skills-can have a substantial impact on the quality of life. Recent studies using noninvasive brain stimulation indicate that priming the corticospinal system by lowering the threshold for the induction of long-term potentiation-like plasticity before skill training may facilitate subsequent skill learning. Here, we used "priming" protocol, in which we used transcranial direct current stimulation (tDCS) applying the cathode over the primary motor cortex (M1) before the anode placed over M1 during unimanual isometric force control training (FORCE_training). Older individuals who received tDCS with the cathode placed over M1 before tDCS with the anode placed over M1 concurrent with FORCE_training showed greater skill improvement and corticospinal excitability increases following the tDCS/FORCE_training protocol compared with both young and older individuals who did not receive the preceding tDCS with the cathode placed over M1. The results suggested that priming tDCS protocols may be used in clinical settings to improve motor function and thus maintain the functional independence of older adults.