Inclusion Criteria:

All subjects must be between the ages of 18-90 and must not be pregnant.

Additional Entry criteria for Stroke subject enrollment:

1. First-time clinical ischemic or hemorrhagic cerebrovascular accident - evidenced by a radiological (or physician's) report;
2. Weakness, defined as score of less than 55 (out of 66) on arm motor Fugl-Meyer (FM) scale
3. Stroke onset >6 months prior to study enrollment.

Exclusion Criteria:

1. Significant pre-stroke disability;
2. Major depression, as defined by Hamilton Depression (HAM-D) scale grater then or equal 17 if needed (history of depression before the stroke);
3. Any substantial decrease in alertness, language reception, or attention that might interfere with understanding instructions for motor testing;
4. Excessive pain in any joint of the paretic extremity (not applicable to severe stroke subjects);

5. Contraindications to single pulse Transcranial Magnetic Stimulation (TMS) (TMS will be used to measure cortical excitability) such as metal head implants

   • history of seizures
   • unexplained loss of consciousness
   • metal in the head
   • frequent or severe headaches or neck pain
   • implanted brain medical devices.

6. Contraindications to tDCS

   • metal in the head
   • implanted brain medical devices
7. Advanced liver, kidney, cardiac, or pulmonary disease;
8. A terminal medical diagnosis consistent with survival < 1 year;
9. Coexistent major neurological or psychiatric disease as to decrease number of confounders;
10. A history of significant alcohol or drug abuse in the prior 6 months;
11. Use of carbamazepine and amitriptyline;
12. Subjects may not be actively enrolled in a separate intervention study targeting stroke recovery and
13. Subjects may not have already received constraint induced motor therapy and/or tDCS treatment for stroke;
14. History of epilepsy before stroke (or episodes of seizures within the last six months).
15. Subjects with global aphasia and deficits of comprehension
16. Pregnancy