Predicting Pain Response to Transcranial Direct Current Stimulation for Phantom Limb Pain in Limb Amputees

Inclusion Criteria: 1. Able to provide informed consent to participate in the study. 2. Subject is older than 18 years. 3. 3 months of phantom limb pain (experienced regularly for at least once a week) after the amputated limb has completely healed. 4. Average pain of at least 4 on a numeric rating scale in the previous week (NRS; ranging from 0 to 10). 5. If the subject is taking any medications, dosages must be stable for at least 2 weeks prior to the enrollment of the study. Exclusion Criteria: 1. Pregnancy or trying to become pregnant in the next 2 months. 2. History of alcohol or drug abuse within the past 6 months as self-reported. 3. Presence of the following contraindication to transcranial direct current stimulation Ferromagnetic metal in the head (e.g., plates or pins, bullets, shrapnel) Implanted head electronic medical devices (e.g., cochlear implants) 4. Head injury resulting in loss of consciousness for at least 30 min or pos-traumatic amnesia for greater than 24 hours, as self-reported 5. Unstable medical conditions (e.g. uncontrolled diabetes, uncompensated cardiac issues, heart failure or chronic obstructive pulmonary disease). 6. Uncontrolled Epilepsy 7. Suffering from severe depression (as defined by a score of \>30 in the Beck Depression Inventory).\* 8. History of unexplained fainting spells or loss of consciousness as self-reported during the last 2 years. 9. History of neurosurgery, as self-reported.