When a traumatic event occurs, the brain has a difficult time processing and storing it like an ordinary memory. Improperly stored memories can cause disturbing feelings, images, sounds, or smells that can be related back to the trauma.  This can cause people to see the world differently and how they relate to others.  EMDR helps with reprocessing the memory so that the traumatic event does not continue to have a negative effect.  The eye movements and/or bilateral stimulation helps the brain store the memory properly.