Modulation Effect of tACS on Chronic Low Back Pain

Inclusion Criteria: 1. Volunteers 18-60 years of age 2. Meet the Classification Criteria of the chronic LBP (having low back pain for more than 6 months) 3. At least 4/10 clinical pain on the 0-10 LBP NRS 4. At least a 10th grade English-reading level; English can be a second language provided that the patients understand all questions used in the assessment measures 5. Meeting the MRI / MEG / EEG screening criteria Exclusion Criteria: 1. Specific causes of back pain (eg, cancer, fractures, spinal stenosis, infections) 2. Complicated back problems (eg, prior back surgery, medicolegal issues) 3. The intent to undergo surgery during the time of involvement in the study 4. History of cardiac, respiratory, or nervous system disease that, in the investigator's judgment, precludes participation in the study because of a heightened potential for adverse outcome (for example: asthma or claustrophobia) 5. Presence of any contraindications to MRI scanning (for example: cardiac pacemaker, metal implants, claustrophobia, pregnancy, cannot lie still in fMRI scanner) 6. Concomitant autoimmune, chronic, inflammatory, neoplastic, and psychiatric diseases 7. Pregnant or lactating 8. Conditions making study participation difficult (e.g., paralysis, psychoses, or other severe psychological problems as per the judgment of a study investigator during Session 1) 9. Active substance abuse disorders (based on subject self-report and drug test) 10. Regular use of pain medication such as opioids, nonopioid analgesics, coanalgesics, corticosteroids, or immunomodulatory agents 11. Any medical conditions, such as peripheral neuropathy, that could affect the results of QST 12. Current use of psychotropic medication