Phantom limb pain (PLP) significantly impairs rehabilitation outcomes and community participation for Veterans with lower limb amputations. PLP is a form of neuropathic pain, where damage or disease affects the nervous system causing uncontrolled pain. Prior neuroimaging research suggests that brain- based changes following amputation contribute to PLP. Changes previously documented include decreased sensory representation of the amputated limb (i.e. sensory map changes) and decreased connectivity between structures. With advancements in neuroimaging, we can now study brain-based changes in persons with lower limb amputations thus informing the design of novel rehabilitation interventions. The objective of this project is to investigate brain-based changes following lower limb amputation to identify neurocorrelates of PLP. There is growing evidence supporting the efficacy of neuromodulation as a non-pharmacological technique for chronic pain including PLP. Neuromodulation is a family of techniques that utilize electrical input to modulate the activity of a region of the brain and includes techniques such as non-invasive brain stimulation (NIBS). By pairing NIBS with existing rehabilitation techniques known to be effective for some with PLP, we can target brain-based changes to reduce PLP. Although there is preliminary evidence of neuroimaging and neuromodulation for PLP, this is unstudied in the Veteran population. Through the Veteran’s Administration (VA) Corporate data warehouse using the Informatics and Computing Infrastructure (VINCI) national database, we learned that the VA Health Care System cares for 36,000 Veterans with amputations where 81% of those Veterans have prescribed opioids for pain. The complexities of post-amputation care are great especially given our Veterans have additional co- morbidities. The long-term goal of this work is to investigate combined, non-pharmacological rehabilitation intervention for PLP in Veterans to be tested with a clinical trial in a CDA-2 proposal. However, before we can investigate the effect of a combined intervention, we must first investigate neurocorrelates of PLP in the Veteran population. The aim of this proposal involves 16 Veterans (ages 18+) with unilateral transtibial amputation (8 Veterans with and 8 Veterans without PLP). First, the Veterans will be asked to complete pain patient- reported outcomes including surveys that examine how pain interferes with daily life and pain-specifics (frequency, duration, description of pain), in combination with survey questions on prosthesis wearing patterns. Second, the Veterans will participate in neuroimaging at the Center for Magnetic Resonance Research (CMRR) at our academic affiliate, the University of Minnesota. Imaging sequences will include two forms of functional magnetic resonance imaging (fMRI). The first fMRI sequence is resting- state to evaluate the connectivity of the brain activity at rest. The second fMRI sequence is a sensory task usin...