We don't know how any form of psychotherapy works in the brain. However, we do know that when a person is very upset, their brain cannot process information as it does ordinarily. One moment becomes "frozen in time," and remembering a trauma may feel as bad as going through it the first time because the images, sounds, smells, and feelings haven’t changed. Such memories have a lasting negative effect that interferes with the way a person sees the world and the way they relate to other people. EMDR seems to have a direct effect on the way that the brain processes information. Normal information processing is resumed, so following a successful EMDR session, a person no longer relives the images, sounds, and feelings when the event is brought to mind. You still remember what happened, but it is less upsetting.