Intervention: tDCS. The primary intervention will be cathodal (inhibitory) tDCS over the contralesional M1. Rationale includes evidence from a phase 1 trial (Kirton 2016, submitted), phase 2 rTMS trial, pediatric tDCS motor learning trial as well as adult stroke rTMS and tDCS trials and developmental animal studies. Inhibitory stimulation over intact, contralesional brain also maximizes safety with more predictable distribution of tDCS currents. Based on previous studies of cathodal tDCS in motor learning, adult stroke rehabilitation and studies of electrode montages in stroke and children140, the following methods will be employed. Soft, replaceable 25cm2 electrodes (Soterix, NYC) will be placed on clean, dry areas of the scalp. The cathode will be placed over the contralesional M1, precisely mapped for each patient using neuronavigated (Brainsight2, Rogue Research, Montreal QU) MRI-TMS co-registration over the hotspot for the contralateral first dorsal interosseous muscle. Consistent with previous tDCS stroke studies, the reference electrode will be placed over the contralateral orbit. The current-controlled model stimulator (Soterix, NYC) will automatically ramp up slowly over 30 seconds to the treatment current of 1.0 mA. tDCS or sham will be administered each day during the first 30 minutes of the daily 1:1 therapy sessions. Co-investigators experienced in pediatric tDCS will perform on-site training and ongoing quality assurance according to standard operating procedures.