How Does Bilateral Stimulation Work? | Why EMDR Therapy is Not Just Eye Movements
EMDR accesses the parts of the brain where traumatic memories are stored, and changes the neural wiring around those memories — through a simple technique called bilateral stimulation (BLS). Learn what BLS looks like in an EMDR session, and why it works so well for trauma reprocessing.
What is EMDR therapy?
EMDR (Eye Movement Desensitization & Reprocessing) is a therapeutic approach that helps you process distressing memories, through a body-based technique called bilateral stimulation.
Through EMDR therapy, you can shift the way that traumatic memories are stored in the brain, decreasing their negative emotional charge.
By the end of EMDR, you might notice that a memory that was 10/10 distressing is now 2/10 or 0/10 (minimally distressing or neutral).
The memory becomes just a memory — instead of a painful experience repeating itself in the present.
What does EMDR look like?
EMDR consists of 8 phases:
(1) Preparation
Your therapist explains the EMDR process and shares techniques (known as “resourcing practices”) for managing emotional distress.
→ To learn more, check out this blog post: Resourcing in EMDR Therapy | What It Is & Why It’s Important.
(2) Assessment
You identify a target memory (or series of memories) to reprocess, such as: childhood trauma, accident, experiences of abandonment and neglect, or any other distressing experience.
Your therapist helps you identify negative beliefs, emotions, and physical sensations associated with the target.
(3) Desensitization
As you focus on the target memory, your therapist guides you through sets of bilateral stimulation (30-60 seconds) to help your brain reprocess the memory. The disturbance associated with the memory gradually decreases.
(4) Installation
The negative beliefs, emotions, and physical sensations associated with the target memory eventually fade away. They are replaced by neutral or positive beliefs, emotions, and sensations, which you “install” in your nervous system through bilateral stimulation.
(5) Body Scan
Your therapist guides you to scan your body from head to toe. If there’s any residual distress associated with the memory, you’ll continue with sets of bilateral stimulation until the distress level is 0 or close to 0.
If you don’t detect anything distressing, you’ll move on to the next steps.
(6) Closure
You and your therapist will review important themes that came up for you, resourcing techniques, and your EMDR aftercare plan.
(7) Re-evaluation
At the next session, your therapist will check if there are any remaining distressing symptoms associated with the target memory. Based on your report, you and your therapist will plan future sessions.
What is bilateral stimulation (BLS)?
Bilateral stimulation (BLS) is used in EMDR therapy to 1) soothe your nervous system, and 2) rewire your brain to heal trauma.
BLS is any type of movement that activates both hemispheres of the brain. It can look like:
moving your eyes back & forth
tapping your arms or knees
listening to alternating tones in your ears
These are the most common types of BLS used in EMDR sessions.
Alternative types of BLS, less commonly used in EMDR but potentially just as effective, include:
tossing an object (stone, ball, fidget) between your hands
drumming
marching in place
walking around
rocking back & forth in a chair
How does BLS work?
The exact mechanisms by which EMDR, or any trauma therapy, works are still being researched. However, there are a couple theories about why bilateral stimulation (BLS) works so well for reprocessing trauma.
(1) BLS TAXES WORKING MEMORY
During EMDR sessions, bilateral stimulation requires you to perform two tasks at once: recalling a distressing memory and following the BLS. This dual taxation is believed to desensitize trauma memories and facilitate the natural healing processes of the nervous system.
While some of your attention is focused on the bilateral movement, distracting your “thinking mind,” the subconscious parts of your brain can work on processing the memory “behind the scenes.”
(2) BLS DISRUPTS NEURAL PATHWAY ASSOCIATED WITH TRAUMA
EMDR is not about talking or thinking your way out of distress. It’s about accessing the parts of the brain where traumatic memories are stored and changing the neural wiring around that memory.
BLS does exactly that. Whether through eye movements, self-tapping, or auditory tones, BLS brings different parts of the brain, across left and right hemispheres, in communication with each other.
New associations and connections are made, old beliefs get “unstuck” – and after enough sets of bilateral stimulation, the target memory becomes rewired in a way that doesn’t cause as much distress as before. The memory becomes neutralized.
Why is EMDR therapy not just eye movements?
(Even though EMDR stands for Eye Movement Desensitization & Reprocessing.)
Psychologist Francine Shapiro developed EMDR in 1987, after noticing that she could more easily process distressing thoughts while engaging in eye movements. She went on to create the 8-phase EMDR protocol, using eye movements as the primary form of bilateral stimulation.
Over time, EMDR has expanded to include other types of bilateral stimulation.
As the therapy gained popularity, it became evident that different individuals respond better to various stimulation methods.
(In fact, some people may be unable to engage in eye movements due to health conditions.)
Some people find auditory stimulation, such as listening to alternating tones, most effective for memory reprocessing. Others prefer tactile stimulation, like tapping on their knees or shoulders.
Flexibility in BLS allows therapists to tailor EMDR treatment to the specific needs, comfort levels, and physical preferences of each client.
What’s the most effective type of bilateral stimulation for trauma reprocessing?
It depends on the person. There’s no one BLS technique that’s 100% effective for everyone, since each nervous system is unique.
During your EMDR sessions, you might alternate through different types of BLS – for example, starting with eye movements, switching to self-tapping, and ending with marching in place.
Your nervous system will give you direct feedback about which BLS is most effective.
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About the Author
Liz Zhou is holistic trauma therapist providing therapy services in Denver, Colorado. She helps highly sensitive, neurodivergent adults and couples heal from the past and connect with their authentic selves. Liz’s specialties include EMDR, IFS, psychedelic integration, and trauma therapy intensives for individuals and couples.
