I apologize I was unable to come on-line yesterday.
The theory behind EMDR is that traumatic events are not processed and stored the same way that other events are processed, but rather remain "stuck" in our brains with all of the original thoughts, feelings, images, body sensations, and beliefs about ourselves. It's like pausing live TV --the event is "stuck," in a way that it should not be, causing all kinds of negative effects (which you are intimately familiar with) .
During an EMDR session both sides of the brain are stimulated in one of several ways --eye movements, tapping (legs or hands), or tones (in ears). You start with a distressing image and allow your mind to go where ever it wants. However, there's a lot of safety built into this process. One safety mechanism is what we call "dual awareness," where you maintain awareness of the present moment (room, person you are with, date, etc) while going to the past --but the goal is to never "get lost" into the past. Some describing as riding a train where you are going to drive past the traumatic scenery.
It's not that you don't feel any pain, fear, or other uncomfortable feelings, but you don't get lost in them as if you were completely there again. Also, there is always the freedom to stop at any time. Before starting EMDR we work a lot on relaxation and the ability to return to safety when necessary. The motto is "go in just as long as necessary to get the job done."
Here's a good website to read more: www.emdr.com
Please feel free to ask more questions --I will be on late tonight and tomorrow morning.