This project will evaluate two different methods of normalizing the center of mass acceleration (COMa) in individuals post-stroke, specifically focusing on rates and pattern of recovery to analyze walking-specific adaptations as precursors to motor learning. In addition, the proposed project seeks to establish the optimal configuration of electrodes to activate neural circuits involved in post-stroke locomotion. Once the better method of training COMa and optimal parameters of electrode placement for tDCS are identified, the investigators will evaluate the effects of tDCS on locomotor adaptations during single sessions and over a five-day training period.

The project seeks to establish the optimal configuration of electrodes to change the excitability of neural circuits involved in post-stroke locomotion, identify effective strategies for training a specific locomotor adaptation, and improve adaptations via adjunctive non-invasive brain stimulation. Tools to improve neural excitability may increase potential for locomotor skill learning, thereby improving rehabilitation outcomes. Non-invasive brain stimulation with transcranial direct current stimulation (tDCS) has recently emerged as a simple to administer, low-cost, and low-risk option for stimulating brain tissue. Cortical excitability is increased after application and preliminary results imply a relationship to increases in motor activity in those post-stroke. However, inhibition of the contralesional hemisphere is also shown to improve paretic motor output through inhibition of excessive maladaptive strategies, and combining the two electrode configurations may provide additional benefit for locomotor tasks requiring interlimb coordination. Furthermore, the effects of tDCS on walking function in conjunction with physical intervention strategies aimed at improving locomotor ability post-stroke are yet unstudied.

Inclusion Criteria: Chronic Stroke

1. age 18-70
2. at least six month post-stroke
3. residual paresis in the lower extremity (Fugl-Meyer LE motor score <34)
4. ability to sit unsupported for ≥ 30 sec
5. ability to walk at least 10 ft.
6. self-selected 10 meter gait speed < 0.8 m/s
7. provision of informed consent.

Exclusion Criteria: Acute Stroke

1. Unable to ambulate at least 150 feet prior to stroke, or experienced intermittent claudication while walking < 200 meters
2. history of congestive heart failure, unstable cardiac arrhythmias, hypertrophic cardiomyopathy, severe aortic stenosis, angina or dyspnea at rest or during activities of daily living
3. History of COPD or oxygen dependence
4. Preexisting neurological disorders, dementia or previous stroke
5. History of major head trauma
6. Legal blindness or severe visual impairment
7. history of significant psychiatric illness
8. Life expectancy <1 yr
9. Severe arthritis or orthopedic problems that limit passive ROM
10. post-stroke depression (PHQ-9 ≥10)
11. History of DVT or pulmonary embolism within 6 months
12. Uncontrolled diabetes with recent weight loss, diabetic coma, or frequent insulin reactions
13. Severe hypertension with systolic >200 mmHg and diastolic >110 mmHg at rest
14. presence of cerebellar stroke.