Reticulospinal pathways are likely key contributors to bilateral disability and recovery that remain understudied. This proposal breaks new conceptual ground by integrating across neuroanatomical, neurophysiological & behavioral domains in stroke. The reticulospinal tract receives input from both hemi-spheres and projects bilaterally, and undergoes neuroanatomical changes in chronic hemiparetic stroke. Neurophysiologically, alpha-band (10-20 Hz) neural drive is exaggerated or redistributed across muscles of both arms after stroke, and this frequency of neural drive is thought to be of reticulospinal, but not corticospinal, origin. We link this to behavior as alpha-band neural drive is especially exacerbated in muscles involved in the pathologic synergies that disrupt motor control. We will demonstrate muscle-muscle coherence is a valid neurophysiological assay to characterize mechanisms of bilateral motor impairment at the level of the reticulospinal tract. Interventions exploiting these mechanisms for recovery of the more-affected arm have a greater chance at being restorative and promoting brain repair than simply improving function through practice of compensatory strategies.