Eye Movement Desensitisation and Reprocessing is now over 25 years old and is considered an evidence-based treatment. The question “Does it work?” has now been replaced by the bigger question “How does it work?”
There are a number of theories but the one that makes sense to me is in the article Eye Movement Desensitization and Reprocessing and Slow Wave Sleep which I will try and summarise as I understand it (all errors of interpretation are mine, email your corrections).
When we experience something overwhelming and relive the traumatic event there is reduced control of the pre-frontal cortex over the activated amygdala and hippocampus (the amygdala and hippocampus become overstimulated). In other words, when you are triggered, the rational thinking part of your brain can’t control the emotional part of your brain. This is why when you get triggered, you can’t think and you feel overwhelmed.
Traumatic memories are “stuck” in the amygdala-hippocampal complex and when triggered, they seem to occur in the present. “Stuck” memories are thought to be unprocessed memories.
During sleep, we process and consolidate memories from the hippocampus to the neocortex. Normal, less traumatic memories, don’t become “stuck”, because at night when we dream (Rapid Eye Movement or REM phase), these are moved out of the amygdala-hippocampal complex and processed by the rest of the brain. This is one of the reasons we feel so much better after a good night’s sleep.
Neuroscientists propose that what happens during REM (dream) sleep happens during EMDR.
During EMDR, therapists move your eyes from side to side whilst getting you to focus on a fragmented traumatic memory or emotion. Much like when your eyes move side to side when you dream.
EEG tracings show that the eye movements (much like in REM sleep) elicit a synchronisation of all cortical activity at a frequency in the delta range like slow-wave sleep. EMDR temporarily slows your over-stimulated amygdala down and synchronises your brain waves helping you process the traumatic memory.
This suggests that during EMDR therapy the traumatic memories are continuously “reactivated, replayed and encoded into existing memory networks”. In other words, EMDR helps traumatic memories become “unstuck” and processed like normal, less traumatic memories.
To quote the article:
“In fact, we posit that bilateral stimulation mimics the low-frequency stimulation typical of SWS (slow-wave sleep), inducing a depotentiation of the AMPA receptors of amygdalar synapses, which in turn lead to a weakening of the traumatic memory. This reduction of the over-potentiation of amygdalar synapses makes traumatic memory more accessible, and facilitates the connection between emotional memory and episodic memory, thus promoting a shift of memory to associative and neocortical areas.”
Essentially, the bilateral movements used in EMDR rapidly allows us to process stuck traumatic memories as we would normally do with less traumatic memories during sleep.
They have a great picture of an EEG tracing that show how the bilateral movements mimic slow-wave sleep. Click to see it in the original article.
EEG tracing upon eye movements during an eye movement desensitization and reprocessing (EMDR) session. Note the slow-wave sleep (SWS)-like frequency from the beginning to the end of bilateral stimulation.
EMDR bilateral stimulation (moving your eyes side to side) mimics slow-wave sleep, calming the amygdala and allowing it to synchronise with the rest of the brain. Thus allowing your brain to process a traumatic memory. What we do in therapy (move your eyes side to side), is what you do every night when you dream.
I probably have not done the article justice so if you enjoy knowing how stuff works like me, have a look at the article.
Remember research regularly overturns previous evidence, perhaps a better explanation will emerge soon. Stay curious.
I look forward to hearing from you.
Clinical Psychologist MAPS
EMDR Accredited Practitioner.
Keywords: EMDR, mechanism of action, eye movements, sleep, slow-wave sleep, REM, orienting response, working memory
Pagani M, Amann BL, Landin-Romero R and Carletto S (2017) Eye Movement Desensitization and Reprocessing and Slow Wave Sleep: A Putative Mechanism of Action. Front. Psychol. 8:1935. doi: 10.3389/fpsyg.2017.01935
Pagani, M., Di Lorenzo, G., Verardo, A. R., Nicolais, G., Monaco, L., Lauretti, G., et al. (2012). Neurobiological correlates of EMDR monitoring – An EEG study. PLOS ONE 7:e45753. doi: 10.1371/journal.pone.0045753