The neuroplastic mechanisms that enable some people with stroke to regain high quality control of their paretic arm post-stroke are unknown. There is broad consensus that the presence or absence of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) over the primary motor cortex is the most useful biomarker to explain treatment response. However, some studies have shown that individuals who are MEP (-) can make clinically meaningful changes in impairment and function. This indicates the need to assess, in detail, the link between MEP (-) status and descending neural connectivity post-stroke. We intend to investigate a biomarker that is cost-effective and that may effectively predict treatment response (e.g., MEPs elicited by direct activation of corticospinal axons). Internationally, there is great interest in the prediction of treatment response post-stroke due to rising medical costs and frustration with minimal improvements in standard of care approaches.