The purpose of this project is to develop the fundamental physiological understanding of feedback controlled vagal nerve stimulation (VNS) using positron emission tomography (PET) brain imaging and blood biomarker measurement with stress in healthy individuals and individuals with PTSD. Healthy human subjects with a history of psychological trauma but without the diagnosis of a psychiatric disorder (Phase 1), and human subjects with a history of PTSD (Phase 2), undergo PET imaging of the brain in conjunction with VNS or a sham treatment during exposure to neutral scripts and scripts of personal traumatic events. Blood is drawn simultaneously for measurement of a variety of stress responsive biomarkers, including inflammatory markers and neurohormones. A second PET scan with biomarkers assesses the delayed effects of VNS. On two other days subjects undergo exposure to random stressors with VNS or sham in conjunction with measurement of stress biomarkers.
