To employ a fear learning-extinction paradigm with functional magnetic resonance imaging (fMRI) and skin conductance response (SCR) assessments among patients with posttraumatic stress disorder (PTSD) and trauma exposed healthy controls, aiming to a) clarify neural circuits underlying PTSD and b) to probe brain based predictors of symptomatic improvement in response to Prolonged Exposure (PE) treatment, and first line treatment for PTSD.