THE SCIENCE OF HEALING
How Does EMDR Work?
Bilateral stimulation, the eight-phase protocol, & the neuroscience behind EMDR.
The Bilateral Stimulation Engine
At the center of EMDR therapy processing is bilateral stimulation — a rhythmic, left-right pattern that engages both hemispheres of the brain. There are several forms: guided eye movements following the therapist’s hand, tactile buzzers or tapping that alternates between hands, auditory tones that shift between ears, or self-administered techniques like the butterfly hug.
Bilateral stimulation appears to mimic what happens during REM sleep, when the brain naturally processes and consolidates experiences. During waking EMDR processing, this stimulation helps the brain access traumatic memories that have been stored in a fragmented, activated state and begin to integrate them with more adaptive information.
What Happens in the Brain
Traumatic memories (or memories that cause overwhelm) are stored differently from ordinary memories. They’re held in the limbic system — the emotional brain — in raw, unprocessed form. The sights, sounds, smells, body sensations, and beliefs from the original events remain linked together and easily activated by present-day triggers.
During EMDR processing, the memory networks begin to connect with more adaptive information. The emotional charge decreases. The body releases the tension it’s been holding. Negative beliefs like “I’m not safe” or “I’m powerless” lose their grip, and more accurate beliefs can take their place. The memory doesn’t disappear — it gets reorganized so it no longer hijacks your nervous system.
Think of it this way: before processing, a traumatic memory triggers the brain’s alarm system as though the danger is still present — like a fire alarm sounding in a building where there is no fire. After processing, that same memory becomes more like a fire report — a record of something that happened, available if needed, but no longer setting off alarms every time it’s recalled.
Competing Theories: Why Does Bilateral Stimulation Work?
We don’t yet have a single definitive explanation. Several well-supported theories exist, and the truth may involve elements of all of them.
The REM sleep analogy proposes that bilateral stimulation activates the same neural processes that occur during rapid eye movement sleep, when the brain naturally consolidates and integrates the day’s experiences. EMDR may essentially be facilitating this process during waking hours.
The working memory taxation model, developed by researchers including Andrade and van den Hout, suggests that bilateral stimulation taxes working memory. Because working memory has limited capacity, holding a traumatic image in mind while simultaneously tracking eye movements or tapping reduces the vividness and emotional intensity of the memory. Over repeated sets, the memory loses its charge.
The orienting response theory proposes that bilateral stimulation triggers a natural investigatory reflex — the brain’s response to new stimuli — which shifts the nervous system from a state of alarm to a state of attentive calm.
One avenue of recent neuroimaging research has been looking into how EMDR processing affects the connectivity between the amygdala, prefrontal cortex, and hippocampus. These three regions form the core circuit disrupted by trauma. The amygdala acts as the brain’s threat detection system; in trauma it becomes hyperreactive, firing alarm signals in response to reminders of past danger even when no real threat exists. The prefrontal cortex is the brain’s rational, observing center — responsible for context, judgment, and the ability to distinguish past from present. Trauma impairs prefrontal function, which is why survivors often cannot think their way out of a triggered state no matter how much they understand what is happening. The hippocampus is responsible for filing memories in time — marking them as “this happened then, not now.” In PTSD, this time-stamping function breaks down, which is why traumatic memories feel present rather than past. Early findings suggest that EMDR may help restore communication between these regions: calming amygdala hyperreactivity, bringing the prefrontal cortex back online, and supporting the hippocampus in properly contextualizing and integrating what was previously stuck.
Other neuroimaging research has begun examining how EMDR processing affects the default mode network — the brain network most consistently associated with self-referential thought, autobiographical memory, and what some researchers describe as the construction of a coherent sense of self. In trauma, the DMN appears to show dysregulated activity: some findings suggest it becomes overactive in ways that keep the traumatic past entangled with present identity, so that old experiences feel less like memories than like ongoing facts about who you are. Early and preliminary findings suggest that EMDR may help normalize DMN activity - reducing the ruminative, self-referential charge of traumatic memories of experiences and supporting their integration as past events rather than present reality.
There are additional mechanisms that likely contribute to what happens during EMDR processing. The anterior cingulate cortex — a brain region involved in cognitive flexibility, error detection, and emotional modulation — appears to play a role in helping the brain resolve internal conflicts during bilateral stimulation. When someone holds contradictory beliefs simultaneously, such as “I know I’m competent” alongside “I feel fundamentally defective,” the brain’s conflict monitoring systems activate. Bilateral stimulation appears to create conditions under which the outdated belief can update — not through logical argument, but through the brain’s own reconsolidation process recognizing the mismatch and resolving it.
This connects to another important aspect of EMDR processing: the brain doesn’t process traumatic memories in isolation. Memories are stored in associative networks — clusters of experiences linked by emotion, sensation, or meaning. When bilateral stimulation activates one memory, it often pulls related experiences into the processing stream. A client may begin with a workplace humiliation and find themselves moving through a childhood memory of being shamed and then a relational betrayal from their twenties — not because the therapist directed them there, but because the brain recognizes the thread connecting all three. This chain processing is one of the reasons EMDR can produce shifts that feel disproportionately large relative to the number of sessions.
Bilateral stimulation also appears to enhance communication between the brain’s two hemispheres via the corpus callosum. One hemisphere may hold the emotional charge of a memory while the other holds the rational understanding that the danger has passed. Without adequate cross-hemisphere communication, these remain siloed — the person knows they’re safe but doesn’t feel safe. The rhythmic, bilateral nature of the stimulation appears to bridge this gap, allowing emotional and cognitive processing to integrate rather than operate in parallel.
Research has also demonstrated that bilateral stimulation specifically reduces the vividness of disturbing visual images — not just the emotional charge, but the sensory intensity of the image itself. Studies show that after sets of eye movements, intrusive images become less vivid, less detailed, and less likely to surface unbidden. For clients who are haunted by visual memories — accident scenes, medical procedures, moments of violence or violation — this reduction in image intensity can be one of the first and most noticeable changes in processing.
Finally, effective EMDR processing depends on what clinicians call dual awareness — the ability to stay connected to distressing material while simultaneously maintaining a grounded, observing presence. Too much distance and the processing doesn’t reach the memory. Too much activation and the client becomes overwhelmed rather than processing. Bilateral stimulation appears to support this balance neurologically, helping the brain maintain the precise level of engagement needed for the memory to be accessed and transformed without flooding the system. This is not something the client has to consciously manage. The bilateral stimulation itself helps regulate the depth of engagement.
What all these theories share is a recognition that EMDR works at a neurological level that talk therapy does not directly access.
EMDR’s Eight Phases
EMDR is sometimes thought to refer to a single technique, but it is much more than that. EMDR is actually an entire therapy system that works through eight phases or components.
Phase 1: History and Treatment Planning. We map your history, identify target memories and their interconnections, and establish treatment goals.
Phase 2: Preparation. Building internal resources, developing somatic awareness, and ensuring you have the capacity to manage what comes up during processing. In my practice, this often includes IFS work to understand the parts of you that may have opinions about this process.
Phase 3: Assessment. Identifying the specific memory to target, the negative belief connected to it, where you feel it in your body, and how disturbing it is.
Phases 4–6: Desensitization, Installation, and Body Scan. This is the active processing — bilateral stimulation while holding the target memory. The disturbance decreases, a positive belief strengthens, and we check for residual tension in the body.
Phase 7: Closure. Ensuring you leave the session grounded and stable, whether or not processing is complete.
Phase 8: Reevaluation. At the next session, we check what’s shifted and what still needs attention.
Integrative EMDR
Standard EMDR is powerful in and of itself. In my practice, I’ve found that integration with other therapy approaches makes it transformative. I weave in Internal Family Systems (IFS) to work with the protective parts that often arise during processing — the part that shuts down, the part that deflects, the part that’s afraid of what comes next. I incorporate somatic therapy because trauma lives in the body, not just the mind. And I work within a relational framework because we heal in connection, not in isolation.
This isn’t a just theoretical preference. It’s what I’ve observed over 30 years of practice: when EMDR is held within a broader integrative container, the work goes deeper, the changes are more stable, and the whole person — not just their symptoms — is addressed.