This study will contribute to the field of stroke rehabilitation research by expanding the investigator's understanding of the neural mechanisms responsible for the development and expression of abnormal flexion synergy, a primary movement impairment due to stroke. The study will longitudinally evaluate motor tract morphology and motor impairment/function in an attempt to develop early neuroimaging-based predictors of the development of flexion synergy and its impact on reaching and hand recovery (6 month). The study will utilize quantitative motor testing (kinematics and kinetics) to measure motor impairment and reaching and hand function. Both neuroimaging and quantitative motor testing will be conducted within 96 hours-, 2 weeks-, 3 months-, and 6 months-post stroke. The knowledge gained by this study will provide crucial structural and functional neuroimaging evidence that demonstrates the timeline of progressive ipsi- and contralesional motor pathway (including bulbospinal pathways) changes and the associated development of flexion synergy that grossly impacts reaching and hand function in individuals with moderate to severe stroke.