Exoskeleton Research: Myoelectric Orthosis for Rehab of Severe Chronic Arm Motor Deficits

Inclusion Criteria: * 18-89 years of age * Unilateral arm weakness due to stroke (6 months or more since onset) * Adequate range of motion at the elbow, forearm, wrist, and hand to don the device * Active shoulder flexion of at least 30 degrees and active shoulder abduction of at least 20 degrees * Ability to generate volitional, consistent, and detectable EMG signals from the upper arm and forearm sensor sites with wrist in neutral or flexed positions as detected by the MyoPro software * MAS score less or equal to 3 for the biceps, triceps, supinators and pronators of the impaired arm * Able to read and comprehend the English language * Able to follow directions * Able to provide informed consent * Medically and psychologically stable. * Ability to don/doff MyoPro independently or have support as needed. * Ability to undergo MRI * Ability to undergo TMS procedures Exclusion Criteria: * Previous stroke(s) affecting motor function on the opposite side. * Persistent and severe shoulder subluxation, pain or dislocation * Shoulder passive range of motion \< 45 degrees in flexion and abduction * Fixed upper limb contractures on the impaired arm and hand * Unable to safely support the weight of their arm plus 4 lbs (1.82 kg; the weight of the device) without pain even with arm supported. * Skin rash or open non-healing wound on impaired arm * Involuntary movements of the impaired arm * Pacemaker or other implanted devices that are not compatible with testing procedures or would interfere with donning/doffing and functioning of device. * Metal in the skull or deformity of the skull * Claustrophobia, or inability to operate the MRI patient call button * Contraindications for MRI (standardized screening form for MRI). * Past history of seizures * Family history of medication refractory epilepsy * Pregnancy or pregnancy planning during the study period * Currently taking medications or substances that lower the threshold for onset of seizure.