Multisession anodal transcranial direct current stimulation induces motor cortex plasticity enhancement and motor learning generalization in an aging population

• Published in: Clinical neurophysiology 2018-02, Vol.129 (2), p.494-502
• Main Authors: Dumel, Gaëlle, Bourassa, Marie-Ève, Charlebois-Plante, Camille, Desjardins, Martine, Doyon, Julien, Saint-Amour, Dave, De Beaumont, Louis
• Format: Article
• Language: English
• Subjects: Brain plasticity; Cortical inhibition; Geriatrics; Motor cortex; Motor learning generalization; Noninvasive brain stimulation
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2017.10.041

•Multisession anodal transcranial direct current stimulation (a-tDCS) of primary motor cortex (M1) induces motor learning generalization in aging.•Multisession a-tDCS-M1 induces M1 cortical disinhibition in aging.•Persistent M1 disinhibition induced by tDCS predicts motor learning generalization. The present aging study investigated the impact of a multisession anodal-tDCS protocol applied over the primary motor cortex (M1) during motor sequence learning on generalization of motor learning and plasticity-dependent measures of cortical excitability. A total of 32 cognitively-intact aging participants performed five consecutive daily 20-min sessions of the serial-reaction time task (SRTT) concomitant with either anodal (n = 16) or sham (n = 16) tDCS over M1. Before and after the intervention, all participants performed the Purdue Pegboard Test (PPT) and Transcranial Magnetic Stimulation (TMS) measures of cortical excitability were collected. Relative to sham, participants assigned to the anodal-tDCS intervention revealed significantly greater performance gains on both the trained SRTT and the untrained PPT as well as a greater disinhibition of long-interval cortical inhibition (LICI). Generalization effects of anodal-tDCS significantly correlated with LICI disinhibition. Anodal-tDCS facilitates motor learning generalisation in an aging population through intracortical disinhibition effects. The current findings demonstrate the potential clinical utility of a multisession anodal-tDCS over M1 protocol as an adjuvant to motor training in alleviating age-associated motor function decline. This study also reveals the pertinence of implementing brain stimulation techniques to modulate age-associated intracortical inhibition changes in order to facilitate motor function gains.