RecruitingClinical trialThe Effects of Very Brief Exposure on PTSD in U.S. Combat VeteransThe goal of this clinical trial is to develop a new behavioral treatment for U.S. combat veterans with post-traumatic stress disorder (PTSD), very brief exposure to combat-related stimuli. The main questions it aims to answer are: 1. How does Very Brief Exposure (combat images and control everyday images) and Visible Exposure to combat stimuli affect brain activity and subjective fear ratings? 2. To what extent are participants aware of the stimuli presented and tolerating the exposures? All participants will view both very brief exposure and visible exposure to combat stimuli in the functional magnetic brain imaging (fMRI) scan. They will provide ratings of fear, awareness, and tolerability. Researchers will compare U.S. combat veterans with PTSD and healthy controls to confirm differences in brain region activation and ratings.