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  • Megan Begley, LCSW

How does EMDR Therapy Work? A More In-Depth Explanation

Updated: Jul 2

Some people just want to know the success rate of a method. For others, however, the more they understand how and why something works, the the more they perceive benefit. If you appreciate details, this post is for you. It explains how EMDR (Eye Movement Desensitization and Reprocessing) was developed, how the brain's normal memory processing is impacted by a traumatic event, and how EMDR acts a course-corrector. It ends with a summary of EMDR benefits in the words of the practitioner who originally developed the treatment approach.


An accidental discovery about eye movements, and the link to emotions and memories


EMDR was first conceived over thirty years ago by Francine Shapiro, a clinical psychologist, after noticing that the intensity of distressing thoughts decreased while moving her eyes back and forth on the ground as she took a walk. Theorizing that eye movements mimic the memory consolidation and emotional processing benefits of REM sleep, she set up a successful clinical trial combining therapist-led, alternating eye movements with traumatic memory processing (re-immersion in the memory).


A fundamental tenet of EMDR is that post-traumatic stress symptoms arise when activation of the sympathetic nervous system, or the fight or flight response, causes a physically or psychologically threatening event to be inadequately processed and stored in memory networks. When an event is too overwhelming to be consolidated with REM sleep, as described below, EMDR creates a waking-life opportunity to reintegrate by re-engaging the brain (and therefore the body, via limbic system connections) in memory processing.


When we're threatened, the brain's hippocampus processes memories differently


Memory processing is a function of the hippocampus, or the right and left hippocampi--one in each hemisphere of the brain. Normally, this brain structure transfers short-term memories into long-term storage in a process involving communication across the hemispheres (bilateral), with a ‘’time stamping’’ effect that files ordinary events away as ‘’the past.’’


When faced with threat, however, this hippocampal function is disrupted for a specific reason: if the memory were shifted to long-term storage, we might not recall it quickly enough to avoid the same danger in the future. It's a behavior-shaping feature designed to support survival by keeping us on alert.


As a result, the event retains a short-term memory status, conveying to the rest of the body that the fight or flight reaction may be still be necessary. If escape or defense is thwarted, or the tension caused by a ''freeze'' response is not later discharged, the biological circuit of autonomic nervous system function (fight or flight, followed by rest and restore) remains incomplete. In other words, the stimulating neurotransmitters and hormones produced in the organs to facilitate action (such as adrenaline and cortisol) remain elevated if the body-mind doesn't receive adequate safety signals, resulting in post-traumatic stress symptoms. At the biological level, it's as if the event never stopped occurring at all.


''Reprocessing'' involves re-engagement of the hippocampus to integrate a memory


After taking some time to help you relax into a state of mindful awareness, the EMDR process itself begins by asking you to close your eyes and re-immerse yourself in the target memory (typically the one causing the most distress.) While this may sound frightening, it recreates the right conditions for the hippocampus to re-engage and ultimately re-process the event within the context of safety.

Although re-immersion is distressing initially, reprocessing of the memory begins relatively quickly by using a form of alternating stimuli to initiate bilateral communication across the hippocampus. While eye movements were obviously the original form of stimuli, later research indicated that alternating tactile or auditory stimulation is also effective (and the Center for HBH in fact uses painless hand buzzers). This evidence led Francine Shapiro to acknowledge that the element of dual attention may actually be the critical component in the treatment's efficacy.


As Shapiro states in this excellent interview, dual attention to both the memory and an external task ‘’...seems to stimulate the brain’s information processing system, and the client then has different, rapidly moving associations...it allows the brain to do the digesting by making all of the appropriate links that it hadn’t been able to make before.’’ In other words, EMDR could be described as providing the body-mind with a second chance to fully integrate an event into a long-term memory, enabling both intense feelings and even biochemical symptoms to be desensitized to some degree at the same time.


Whether eye movements or another stimulus is used, as dual attention enables reprocessing to begin, so does the desensitization element of the therapy. The distress level associated with the target memory begins to decrease--typically both as the session progresses, and also in a way that usually endures after the treatment.


EMDR also builds resiliency by reframing your beliefs about the event and your past


As desensitization occurs, not only does the intensity of the memory become less charged, but shifts in associated negative beliefs-- about yourself or the world--begin to naturally shift. Often, these beliefs prove to be connected to other lifetime events, creating the opportunity to begin healing a network of trauma. As Shapiro notes, ‘’emotions, physical sensations, beliefs--all of those shift to a level of learning and resilience.’’


In a 2019 article for BrainWorld, Shapiro also writes:


“EMDR therapy places the information-processing system of the brain first and foremost in both the development and treatment of pathology. This system functions to take disturbing events and make the appropriate connections that allow a return of emotional equilibrium. For instance, a fight with a family member may cause us to have negative emotions, thoughts and body reactions, but they are usually resolved through thinking about it and during the period of rapid eye movement (REM) sleep. We may end up feeling, He must have been having a bad day. We’ve had good experiences before and can resolve this glitch. This resolution occurs because our brain has made the appropriate connections, and our negative reactions disappear. But when an event is too disturbing, it can overwhelm the information-processing system, and this negative experience is stored in memory along with the unpleasant emotions, physical sensations and beliefs. Since everything that happens in the present links into the memory networks to be interpreted, any future encounter with the person can trigger these unprocessed memories and the negative responses arise.''


Shapiro continues, ''Rather than rely on the deliberate manipulation of beliefs and behaviors as occurs in cognitive behavior therapy, or the use of the relationship as in psychodynamic therapies, EMDR therapy identifies the earlier life experiences that are the basis of current problems and, after accessing the memories of the events, activates the brain’s information-processing system.”



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