Auricular Vagus Nerve Stimulation for Chronic Pain

Inclusion Criteria: * Volunteers 18-65 years of age. * Meet the Classification Criteria of chronic LBP (having low back pain for more than 6 months), as determined by a referring physician. * Received stable treatment or no treatment in the past month. * At least a 10th grade English-reading level. English can be a second language provided that the patients feel they understand all the questions used in the assessment measures. Exclusion Criteria: * Specific causes of back pain (e.g., epidural abscess, compression fracture, spondyloarthropathy, malignancy, cauda equina syndrome) or radicular pain, radiculopathy, or spinal canal stenosis. Complicated back problems (e.g., prior back surgery, medico-legal issues). * Presence of headache/migraine, as well as widespread body pain such as fibromyalgia. * The intent to undergo surgery during participation in the study. * 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 outcomes (e.g., asthma or claustrophobia). * Presence of any contraindications to MRI scanning (e.g., cardiac pacemaker, metal implants, fear of enclosed spaces, pregnancy, cannot lie still in fMRI scanner). * Conditions that might confound longitudinal effects or interpretation of results (e.g. severe fibromyalgia, rheumatoid arthritis). * Pregnant or lactating. * 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). * Active substance abuse disorders within the last 24 months (based on subject self-report). * Use of prescription steroids for pain during the past six months. * Presence of any other acute or chronic pain disorder. * Any medical conditions, such as peripheral neuropathy, that could affect the results of QST.