My experience of EMDR therapy and the brain is that there is a kind of unraveling that occurs. The brain is allowed to flow freely and link different times and events to come to the resolution it needs. I am able to stay partly in the room and partly in the image I am working with.
I find the emotions come like waves. Throughout the processing, I might be feeling anger and then sadness, and then a sense of calm and resolution. I have found the original image sometimes becomes kind of fuzzy and sometimes is still clear, but I am doing something different in the image.