What Happens to Memory During Trauma?

by Monica A. Ross, LPC

Eye Movement Desensitization and Reprocessing (EMDR) works by utilizing something called dual attention stimuli. The session itself consists of the therapist leading the client through a series of either eye movements or tapping and auditory tones. Dual attention refers to the technique of the client being focused both on the traumatic memory and on the eye movements or tapping and auditory tones at the same time. Think of it kind of like this. There is the traumatic image or thought in your brain with all of its terror and then at the same time you are holding this other space of nonterror, of peace and calm. That other place is in a way beckoning you out of the disturbing image and thought.

And the funny thing is at some point during the process it’s almost as if you realize that that other thing—the place of peace—it was there with you during the terror all along. It’s just that at the time of the trauma your brain went offline and lost connection with it.

That’s how I like to think of it anyway. We’re supporting the brain’s ability to heal itself. As therapists utilizing EMDR we’re not here to put stuff into your brain as much as we are stepping back and letting your brain do its thing to restore itself in the best way it knows how.

It’s difficult talking about the usage of this technique both as a clinician and as someone having gone through it myself, because it feels a bit like things get a little abstruse and non intentionally.

So what’s happening in that moment of trauma when the brain goes offline?

Let’s talk a little bit about the brain and its structures. First we have the prefrontal cortex. The prefrontal cortex is involved in executive functioning. We use it to focus and set our attention on something.

Because the prefrontal cortex collects general knowledge it enables us to generalize and anticipate the future. When our limbic brain wants to react, the prefrontal cortex helps us to separate out present day experience from what might be triggering our past experience.

It helps us to control ourselves in situations where our boss says something that we may have heard from a caregiver in the past and to distinguish from the intent of our boss’s comment the intent of the comment that came from our abusive caregiver. So that maybe in that example we have social reserve and don’t fly off the handle.

The thalamus allows for the transfer of information between different parts of the brain and helps with things like regulating states of sleep. It also assists with motor functioning. The thalamus receives all of the information coming into the brain and does the initial sorting of it to the various places it needs to go.

It sends explicit memory information to the hippocampus and implicit memory information to the amygdala. Explicit memory is composed of facts and general knowledge. It places us in space and time. Implicit memory is composed of emotional responses and bodily sensations.

Implicit memory holds our reflexes and any classically conditioned responses we might have. Implicit memory does not help with the recalling of self in space and time. With implicit memory we remember our heart racing, the impulse we had to pull away, the physical pain we may have experienced from the event.

The thalamus sends implicit information to the prefrontal cortex, but this information has to go through additional layers of processing and gets to the amygdala first.

So that when we see a bear and run, because the information hits the amygdala first, we might first think fight/flight/freeze and run automatically and then the prefrontal cortex might later come online with how fast to run and where to run, etc.

The amygdala is the brain’s smoke detector. It scans the environment for danger and determines if, like in the example above, we need to fight/flight/freeze. The amygdala processes implicit information. If it perceives danger, it initiates a response.

The hippocampus processes a substantial amount of explicit data and moves that data through sequential stages of memory—sensory memory, working memory, long-term memory, and cortical consolidation.

Traumatic events disrupt the processing of information by the brain instantly because of the extreme arousal they cause. All of the parts of the brain discussed are affected except for the thalamus. The thalamus continues to sort.

In a traumatic event a rapid rise in neurotransmitters, especially norepinephrine, take the prefrontal cortex offline. Cortisol and adrenaline also rise. This makes the hippocampus shut off because it is sensitive to these hormones.

So information continues to be taken in and sorted by the thalamus, but it does not get processed because all of these other structures shut off. Think about that. That means the orienting of place and time, the accessing of facts and general knowledge, the bodily sensation and emotions—all of that does not integrate.

The deletion of information doesn’t occur in the same way because of the hippocampus going offline, so there is all of that information we have taken in both explicitly and implicitly and it’s all sitting there en masse disconnected and fragmented.

Memory becomes unprocessed, in other words, and is frozen or neurologically held in its original disturbing state. So that even though we might take in new information as we leave the event and go about living our daily lives, our memory of the trauma remains pretty stable and unaltered.

For example, the person who gets bitten by a dog at the age of 3—even though they have spent the past 20 years walking through neighborhoods never getting attacked by dogs—still might have fear when they take a walk at the age of 22. They may see from the periphery of their vision a dog getting loose from its owner’s leash and their heart may stop a little.

Again, much of the explaining that I’m doing of the brain and its structures and ways of processing information I culled from Rick’s presentation on EMDR this past weekend in Austin.