P 181. Impact of offline transcranial direct current stimulation on consolidation of motor sequence learning in healthy elderly subjects

Abstract

Stroke is a major cause of chronic disability in older adults, with higher level motor function often adversely affected. The rate of motor skill acquisition does not seem to differ between young and older adults, but the consolidation process seems to be impaired in the latter group. Studies investigating young and healthy subjects found that online application of transcranial direct current stimulation during motor training improves performance and consolidation of the trained task. Several studies on stroke patients suggested beneficial effects of online tDCS on motor rehabilitation. We investigated whether enhancing excitability in the primary motor cortex (M1) and premotor cortex (PMC) via anodal tDCS immediately after motor training improves consolidation of motor sequence learning in healthy elderly subjects. 26 healthy elderly subjects (mean age 65.4 y, 16 female) were included. Anodal tDCS (15 min, 1 mA, 35 cm 2 electrodes) or sham-tDCS was applied over left M1 or PMC immediately after completion of the explicit motor sequence training. The motor sequence training consisted of 14 blocks with 25 s rests between blocks. Subjects were instructed to perform a five element sequence (4-1-3-2-4, 1 = Dig. II, 4 = Dig. V) with their right hand as fast and accurate as possible. The sequence was practiced 12 times per block. Subjects were retested (4 blocks) 8 h (in the evening) and 22 h (next morning) post training and speed (times per correct sequence) was evaluated. The ANOVA over both retests revealed a main effect for “group“ regarding improvement of performance compared to the end of training (last 4 blocks) ( F = 10.444, p = 0.001). Post hoc t -tests show that this effect is driven by the improved performance of the M1 group (M1 vs. SHAM: p = 0.001, M1 vs. PMC: p = 0.006, SHAM vs. PMC: p = 1.000). No interaction of group ∗ time of retest was found. Offline application of anodal tDCS over M1 post training improves consolidation of motor sequence learning in elderly subjects until at least 22 h post training. Further studies are needed to investigate the potential benefit of offline-tDCS in motor learning in healthy elderly and stroke patients.