Photosensitivity is one of the more common sequelae of TBI, with over 50% of TBI patients reporting some level of photosensitivity in the acute and/or chronic stages. Photosensitivity can range from mild to severe and can significantly impair social, physical, and cognitive functioning, as well as rehabilitation outcomes. While spectacle chromatic filters (i.e., sunglasses or indoor tints) are conventionally used to alleviate symptoms, they are not designed to resolve issues with photosensitivity and have been associated with lower symptom recovery over time, underscoring the need to develop more effective, non-invasive treatment options that can reduce or eliminate photosensitivity. Recent work has shown that neurofeedback interventions, such as Low Intensity Pulse-Based Transcranial Electrical Stimulation (LIP-tES) may be effective in treating post-concussive symptoms and a preliminary case study from our research group suggests that LIP-tES may also be able to reduce photosensitivity symptoms in veterans with a history of mild TBI. This represents an important opportunity to address an area of high priority to Rehabilitation R&D, namely “the development of technology- based interventions for chronic painful conditions that negatively impact outcomes”. However, both the mechanism by which LIP-tES alters brain activity and alleviates symptoms across a range of disorders remains unclear as does the neurobiological basis of photosensitivity associated with mTBI and psychiatric comorbidities commonly seen in today’s Veteran population. These knowledge gaps represent important limitations both for the clinical characterization of photosensitivity in Veterans and development/optimization of novel treatment options. This proposal will take an important first step in addressing these two important knowledge gaps. Aim 1: Complete a preliminary study testing the feasibility and acceptability of a novel LIP-tES intervention designed to reduce severity of PS in patients with a history of mTBI. Extending a recent case study completed by our research group, we will continue investigation of this novel intervention by completing a pilot study of LIP-tES for the treatment of PS in veterans with a history of mTBI. Across 12 LIP- tES and 12 sham sessions we will track recruitment capability (participants screened vs. enrolled, attrition rates and reasons for attrition), acceptability and suitability of the intervention, evaluate suitability of the sham procedure we developed, and gain preliminary evaluation of participant responses to the intervention. Aim 2: Assess neurophysiological markers of PS and changes associated with LIP-tES intervention using resting-state fMRI. Half of the participants enrolled in the study will complete three MRI scans during the initial visit, midway through the study, and after the last LIP-tES or sham session. Preliminary work from our laboratory has identified a sparse connectome of regions that are predictive of moderate/severe ...