Transcranial direct current stimulation (tDCS) is a type of non-invasive brain stimulation that may enhance the likelihood of neuronal activity in the VMPFC. In doing so, tDCS prepares the brain to respond to external stimuli and to facilitate learning and memory. Because therapeutic success from exposure to trauma-related content - as used in exposure-based therapy for PTSD - is thought to be based on an adaptive learning process, applying tDCS in combination with exposure to trauma cues may effectively boost exposure-based learning. To do this, investigators at the Providence VA Medical Center will use a standardized virtual reality (VR) setting to deliver trauma-related content. The virtual reality setting involves three, 8-minute driving scenarios, which consist of VR stimuli (sights, sounds, smells, etc.) often encountered in combat training and in theater.