B. TMS: Robotic motor mapping. TMS studies will occur at the ACH Pediatric Brain Stimulation Laboratory, a state-of-the-art, child-friendly facility that has completed >3 million stimulations in >280 children (Zewdie, unpublished) without complication. The investigators are the first pediatric centre in the world with the Axilum TMS Robot72 and have developed a rapid motor mapping technique (see Figure 2). Using each subject's anatomical MRI and neuronavigation (Brainsight2), a 10x10 grid with 7mm spacing will be placed over M1. A recently developed rapid mapping protocol (4 stimulations per site) will obtain mean MEP values for each active site. The robot allows precise targeting with real-time motion correction and rapid mapping. The primary TMS outcome will be area-under-the-curve of customized heat maps of contralesional motor cortex. Multiple upper extremity muscles will be simultaneously mapped from both hemispheres including dedicated ipsilateral projections from the contralesional hemisphere. Primary outcomes are motor map area, volume, and center of gravity. Additional TMS measures will include corticospinal tract arrangement, motor thresholds, MEP latency, and cortical silent period. The investigators have successfully demonstrated these methods in children with stroke.