When we experience something traumatic, that means that our brain's emotional system is too overwhelmed. Therefore, you cannot access the part that regulates our emotions. Our emotional brain is like airport security, constantly scanning incoming information to ensure no signs of threat. Trauma, or adverse experiences, make airport security go on complete lockdown, tagging anything that remotely looks dangerous. This "full lockdown" can look like panic attacks, constant anxiety, being alert or on guard, conflict in relationships, misunderstanding what people say or their intentions and an overall sense of dread. The part of our brain that regulates our emotions is like the airport security personnel, watching the scanner and, even if an alarm goes off, being able to check to see if it is worth worrying about.

EMDR takes advantage of the fact that memory is a process and that this process can have things added or taken away, and with enough training, you can manipulate what you add or take away from a memory. Imagine building a tower out of Lego bricks, and there are different colours and sizes of bricks. Then, imagine someone comes over, knocks over your tower, takes away 10 pieces, and then asks you to build the same tower. You can do it, but there may be holes in your tower from the bricks that were taken away. Your brain automatically will fill these holes with material or information that makes the most sense. If there is a bunch of blue bricks, then your brain may fill in a gap with a blue-looking brick, etc. With trauma, these holes may be negative beliefs about ourselves or simply being stuck on certain parts of the tower (hyper-fixing on specifics of a memory).

EMDR allows a clinician with the client to manipulate how the brain may fill some of those gaps, thereby altering or making the tower into something much more manageable and less disturbing. It is taking all the pieces of Lego and being more in control of remaking the tower into something manageable and whole. Perhaps a yellow brick is a better choice to fill some of the gaps in the memory than a blue one. This could replace "I am in danger" with "I am safe now." Even though "I am in danger" could fit with the memory, that may become problematic over time. Changing it to "I am safe" could make the whole tower less scary and easier to manage going forward.