A. MRI: Connectivity and chemistry. Images will be acquired on dedicated 3T research scanners across centres using standardized protocols within established neuroimaging networks. Baseline imaging will be performed within 4 weeks of intervention. Post-intervention imaging will be performed 5-7 days after the last day of treatment and at 6 months following treatment. Scan time will be ~60 minutes. Anatomical imaging following established perinatal stroke protocols includes T1- and T2-weighted 3D BRAVO anatomical sequences. For task fMRI, subjects will perform contraction of affected hand and unaffected hand in an event-related design. In response to a cue, participants will squeeze an air-filled bulb attached to a pressure transducer that quantifies grip pressure. A static fixation cross will indicate to stop and rest for 14 seconds. Brain activity in response to each hand movement will be determined using SPM12 by employing a General Linear Model. Registration to each participant's anatomical images will be performed using reverse deformation fields from SPM segmentation. Outcomes include extent of blood-oxygen level dependent response (BOLD) activation, peak locations and M1 laterality index (LI). For resting state MRI acquisition, children will be instructed to lie still with eyes open. Resting-state fMRI BOLD signals will be extracted from each M1 and other areas of interest as defined above with temporal cross-correlation. Correlation coefficients will be Fisher transformed and entered into a random effects General Linear Model consistent with validated methods. Outcomes include intrahemispheric (M1-S1) and interhemispheric (M1-M1) connectivity. For white matter connectivity, diffusion tensor imaging will include 60 directions (b-values= 0,2000s/mm2). Voxel size is 2.5mm isotropic. Fractional anisotropy (FA), color coded-FA, ADC, and b0 maps will all be generated in MRTrix3. A multi-ROI approach will generate tracts of interest using probabilistic tractography. Outcomes will expand previous experience interrogating corticospinal, somatosensory, and transcallosal tracts. Metabolite concentrations in bilateral M1 will be measured via magnetic resonance spectroscopy (MRS), providing information about neuronal and cell membrane health, energy metabolism, health of glial cells and excitatory neurotransmitters. Preliminary data from the APSP has demonstrated the feasibility of these methods in children with perinatal stroke. Established neuroimaging experts will ensure optimal comparability between centres according to predefined protocols. The centralized imaging repository system of the Stroke Imaging Lab for Children (SILC) supported by Brain Canada will use established protocols and systems (BrainCode) for anonymized online transfer of images to and from site investigators.