Project Summary The proposed project is a clinical trial of a mindfulness-based neurofeedback (mbNF) intervention used to augment Dialectical Behavior Therapy (DBT) skills group training in adults with borderline personality disorder (BPD). DBT is the best-evidenced treatment for BPD. Its full implementation involves up to 20 hours per week of clinical contact for 6-12 months. Recent studies have shown that weekly brief DBT skills groups (DBTsg) also provide clinical benefit for people with BPD. Here, we propose to amplify DBTsg training with mbNF. Mindfulness is a foundational skill for DBT that is emphasized throughout each DBT module. Our aim is to strengthen the ability of subjects to practice mindfulness effectively, and thereby to amplify the therapeutic benefits of DBTsg. In our study, people with BPD will enroll, participate in a real-time fMRI mbNF intervention, and subsequently participate in DBT. The mbNF intervention involves engaging in mindfulness meditation while receiving feedback on how well one's brain patterns reflect a focused mindful state in which the fronto- parietal control network (FPCN: controls cognitive focus) has high activity while the default mode network (DMN: associated with less mindful brain state) has low activity. We hypothesize that mbNF will strengthen the brain circuitry supporting mindfulness and thereby amplify the clinical benefits obtained in the DBTsg. Our past studies using mbNF have demonstrated that it decreases hyperconnectivity within the DMN, increases anticorrelations between the DMN and FPCN, increases connectivity between frontal control regions and amygdala, improves measures of state mindfulness, and yields clinical benefits in neuropsychiatric populations. The proposed study adopts a randomized, double-blind trial design to examine whether mbNF in patients with BPD induces the expected changes in DMN connectivity (decreased internal connectivity and increased anticorrelations to FPCN). We will also test whether mbNF amplifies clinical efficacy of DBT. Efficacy on both brain and clinical measures will be determined via comparison to a control group that receives yoked sham feedback and DBT. Importantly, the persistence of training effects will be monitored over several months. Neurofeedback naturally supports a closed loop intervention development cycle in which neuroscientific and clinical knowledge develop together. The proposed study would leverage this approach in the development of novel therapeutic options for BPD. It will inform our understanding of the neural substrates supporting clinical efficacy of DBT in BPD and could lead to development of the first neuroscience-based treatment option for patients with BPD.