Phenotyping Response to Spinal Cord Stimulation in Chronic Low Back Pain

Inclusion Criteria: * Able to give informed consent for participation in the trial and be able to comply with study-related requirements, procedures, and visits * Male or female, between the ages of 18 and 80 years (inclusive) * Current self-report of chronic low back pain (pain between the lower posterior margin of the rib cage and the horizontal gluteal fold), which has persisted for \> the past 3 months AND has resulted in pain on \> 50% of days in the past 6 months\* (\*Chronic low back pain criteria as defined by the NIH Pain Consortium Research Task Force (RTF) and BACPAC Minimum Dataset Working Group) * Already undergoing spinal cord stimulator treatment for chronic low back pain * Able to use their lower extremities * Able to tolerate fMRI and neurophysiological evaluation Exclusion Criteria: * Significant decision-making incapacity preventing informed consent * Any medical condition that could interfere with study procedures, accurate pain reporting, and/or confound evaluation of study endpoints, as determined by the Investigator. * Lifetime history of psychiatric disorder (schizophrenia, bipolar disorder with psychotic features, or other psychotic disorder), or current suicidal ideation * Any stimulation device and/or implant other than a spinal cord stimulator, such as a drug pump, pacemaker, deep brain stimulator (DBS), or sacral nerve stimulator (SNS) * Life expectancy of less than 1 year * Pregnant or nursing (if female and sexually active, patient must be using a reliable form of birth control, be surgically sterile, or be at least 2 years post-menopausal) * Any documented history of substance abuse (narcotics, alcohol, etc.) or substance dependency (not including marijuana use) * Participation in another clinical trial currently or within the past 30 days * Current treatment with electroconvulsive therapy (ECT) or transcranial magnetic stimulation (rTMS) * Conditions that preclude assessing brain function by fMRI: previous head injury, brain surgery, dementia, spinal cord injury, traumatic brain injury, cortical atrophy, serious neurological or medical illness, psychiatric illness, development disability, sensory impairment such as vision and hearing loss, history of birth weight less than 2000 grams and/or gestational age less than 34 weeks) * MRI compatibility: No major contraindication to MRI (e.g. claustrophobia, pacemaker, vascular stents, metallic ear tubes) and metal implants that would preclude use of MRI * History of spine surgery with existing instrumentation failure (i.e., broken screws or rods) or pseudarthrosis (lack of fusion) that could be the cause of CLBP * Any other comorbidity or condition that, in the opinion of the Investigator would make the subject unsuitable for the study or unable to comply with the study requirements