A clinical trial is exploring if a new system called Prism can help reduce PTSD (Post-Traumatic Stress Disorder) symptoms. PTSD is a condition where someone keeps reliving a terrible event. Prism uses EEG, which stands for Electroencephalogram, to help people control their brain activity. EEG is a test that records brain wave patterns. Researchers will compare Prism training to a "sham" training, which looks like real training but doesn't provide actual brain feedback. Participants will attend two one-hour sessions each week for about 8 weeks, followed by two additional sessions a month and two months later. There will be three interviews: before starting, after nine weeks, and a month after the last session. **Key Points:** - The study involves 15 training sessions and 3 interviews over approximately 20 weeks. - Participants need to be comfortable with regular sessions and interviews. - Participants must be stable on any mental health medications before and during the study. This trial is for military veterans and civilians with PTSD, but certain medical conditions or treatments might exclude someone from participating.