Mapping Corticoreticulospinal Motor Control in Chronic Hemiparetic Stroke

Inclusion Criteria: * Adults aged at least 18y * Able to perform shoulder abduction task (confirmed during screening and initial examination) * Safe to undergo MRI * Able to follow visual instructions using MRI-compatible vision correction goggles * No brainstem or cerebellar lesions * No severe concurrent medical problems * Cognitive/attentional capacity to focus on a task * Able to communicate in English or Spanish Additional inclusion criteria for stroke participants: * Have sustained only one unilateral subcortical, ischemic lesion in the territory supplied by the Middle Cerebral Artery (confirmed by clinical or radiological reports) at least one year prior to participation in this project * Paresis confined to one side, with moderate-to-severe motor impairment of the upper limb (Upper Extremity Fugl-Meyer score between 10 and 45). Exclusion Criteria: * MRI contraindications * Severe claustrophobia * Pregnant women * Prisoners * Vulnerable populations * Diagnosis/history of: * multiple sclerosis * brain tumor * brain radiation * traumatic brain injury * dementia * Parkinson's disease * Concurrent enrollment in an intervention study * Concurrent use of medications known to suppress central nervous system activity