The Neurology of Eye Movement Desensitization and Reprocessing (EMDR): How it Works to Treat Trauma

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We know from observational and experimental research, and brain imaging, that EMDR decreases activity in areas of the brain that are typically disrupted by traumatic stress such as the thalamus, hypothalamus, amygdala, and caudate nucleus, all of which are located in the interior regions of the brain, and all of which are involved in emotion, fear response, sleep, and memory, and in the case of the caudate nucleus, also influence motor control. We also know that EMDR activates activity in hippocampal and higher cortical areas of the brain related to problem solving, analysis, memory processing, and meaning-making. This combination of effects appears to recalibrate brain function, returning it to a state that is closer to what we would see pre-trauma—and the effects are lasting.[1]

EMDR theory itself labels what is happening in the brain during therapy as Adaptive Information Processing (AIP), which it is believed is directly related to be generated by bilaterial stimulation (BLS). Initially, BLS was achieved through eye movement, which is usually considered to be preferable if possible, but is often now achieved through other means as well such as bilateral tapping, buzzers, alternating sounds, etc.

Imaging Studies

There are numerous imaging studies (fMRI, EEG, SPECT, MRI) for EMDR, showing that it changes brain activity and structure, reducing hyperactivity in fear centers like the amygdala and increasing activity in frontal regions, which helps process traumatic memories by normalizing brain networks involved in emotion regulation and memory consolidation. These studies reveal that EMDR normalizes the hippocampus and amygdala function supporting its effectiveness for PTSD. 

Types of Imaging Used

  • fMRI (Functional Magnetic Resonance Imaging): Shows changes in brain activity and blood flow during tasks, revealing reduced amygdala response and increased prefrontal cortex activity after EMDR.
  • SPECT (Single Photon Emission Computed Tomography): Used to observe regional cerebral blood flow, showing patterns of activation in areas like the anterior cingulate gyrus and thalamus after treatment.
  • EEG (Electroencephalography): Measures electrical activity, showing shifts in brain activation from emotional to more integrated areas during EMDR sessions, correlating with symptom improvement.
  • MRI (Magnetic Resonance Imaging):Used for structural analysis, though changes in volume (like the hippocampus) might take longer to appear. 

Key Findings

  • Amygdala & Fear Response: EMDR reduces the exaggerated response of the amygdala (the brain’s fear center) to trauma cues.
  • Prefrontal and Dorsolateral Cortices (PFC and DLC) Activation: Increases activity in the PFC and DLC, which helps with emotion regulation, higher cognitive functions, and executive control.
  • Hippocampal Function: Helps normalize the hippocampus, a key memory structure often affected in PTSD.
  • Memory Reprocessing: Imaging suggests EMDR helps move traumatic memories from limbic (emotional) areas to neocortical (semantic/narrative) networks, integrating them better. (This may partially explain how trauma memories and sensations become less intense and acute after EMDR treatment).
  • REM Sleep: Sleep studies show that REM sleep improves after EMDR treatment.
  • Attention: Executive function and increased ability to focus, particularly over time, improve after EMDR treatment. (This is likely a combination of decrease in threat response networks and increase in neocortical activity).

Conclusion
Neuroimaging studies and other research provide biological evidence that EMDR therapy is far more than a psychological technique; it induces real, measurable changes in brain function and structure, helping to desensitize and reprocess (EMDR) traumatic memories for better neurocognitive and mental health outcomes.

References

de Jongh, A., de Roos, C., & El-Leithy, S. (2024). State of the science: Eye movement desensitization and reprocessing (EMDR) therapy. Journal of Traumatic Stress, 37, 205–216. https://doi.org/10.1002/jts.23012

P.F. Rousseau, M. El Khoury-Malhame, E. Reynaud, X. Zendjidjian, J.C. Samuelian, S. Khalfa, Neurobiological correlates of EMDR therapy effect in PTSD, European Journal of Trauma & Dissociation, Volume 3, Issue 2, 2019, Pages 103-111, ISSN 2468-7499, https://doi.org/10.1016/j.ejtd.2018.07.001

[1] While this brief article focuses on trauma, there is expansive, peer-reviewed research that also validates EMDR for treatment of depression, anxiety, addiction, ODC, and other mental health symptoms/conditions.

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