Neural Operant Conditioning

Inclusion Criteria: 1. Sign and date consent form 2. At least 3 months since stroke event 3. Over 18 years of age at time of eligibility 4. Ability to stand upright and walk for at least 5 minutes 5. Premorbidly independent 6. Mild to moderate gait impairment 7. Reduced knee flexion during walking relative to the unimpaired side 8. Unilateral hemiparesis of the lower limbs 9. Ability to evoke muscle responses through peripheral nerve stimulation, spinal cord stimulation, and transcranial magnetic stimulation 10. Medically stable 11. Skin intact on hemiparetic leg, abdomen, and scalp 12. Ability to evoke muscle responses and/or reflex responses through peripheral nerve stimulation, spinal cord stimulation, and/or transcranial magnetic stimulation Exclusion Criteria: 1. Co-existing neurological condition other than prior stroke involving the hemiparetic lower limb (e.g., peripheral nerve injury, PD, SCI, TBI, MS). 2. History of lower limb musculoskeletal injury 3. Functionally relevant osteoarthritis and weight bearing restriction 4. Functionally relevant polyneuropathy resulting in lack of sensation in the lower leg 5. Functionally relevant cognitive impairment 6. Functionally relevant vision impairment 7. Pregnant 8. Botox injection to the ipsilateral leg in the last 12 weeks or taking oral anti-spasticity medications 9. Taking part in physical therapy for any walking-related impairment 10. Cardiac pacemaker or other implanted electronic systems 11. Uncontrolled seizure disorder 12. Use of seizure lowering threshold medications and the discretion of the study physician 13. Deficits in communication that interfere with reasonable study participation 14. Severely impaired cognition and communication 15. Severe lower limb pain