What is Bilateral Stimulation? (The Key to Brain-Body Healing in EMDR Therapy)
What do eye movements, self-tapping, and audio tones have in common? They’re all forms of bilateral stimulation that can help your brain heal from stress & trauma.
As an EMDR trauma therapist, I witness the brain and body’s natural healing processes every day – and it never gets old. EMDR, or Eye Movement Desensitization and Reprocessing, is a powerful therapy that allows the nervous system to process stressful and traumatic experiences in a safe and lasting way.
What makes EMDR so effective? The answer lies in a simple yet potent technique called bilateral stimulation (BLS).
Bilateral stimulation activates natural healing properties in the brain & body.
Imagine a butterfly flapping its wings. Notice how the movement happens on both sides, in a back-and-forth rhythm. Bilateral stimulation replicates this concept, activating both sides of the brain in a rhythmic way. Different regions of the brain get to connect, exchange information, and reorganize neural pathways through the BLS process.
What does bilateral stimulation look like?
Here are the 3 most common methods.
Tapping: gently tapping your knees or arms, alternating sides.
Auditory tones: listening to headphones with tones alternating between ears.
Eye movements: moving your eyes back and forth, while keeping your head still.
For in-person EMDR therapy, your eyes might follow a therapist’s finger moving back and forth across your visual field; or a light bar that acts as a visual metronome.
For online EMDR therapy, your therapist might send you a link to a BLS website, where you’ll see a ball moving back and forth across your screen. You’ll follow the ball with your eyes as it travels. The website allows the therapist to control the stimulation remotely if needed (i.e., changing the speed, color, or direction of the ball).
How does bilateral stimulation work?
The exact mechanisms of bilateral stimulation are still being researched. The brain is a massive, complex, and intricate organ, after all! Here are a few compelling theories.
Enhanced Processing
When we experience a trauma, the brain prioritizes immediate survival over long-term processing. This can lead to the formation of a fragmented memory capsule. The sights, sounds, smells, emotions, and physical sensations surrounding the event get stored together, but the brain struggles to integrate this experience into our overall understanding of ourselves and the world.
These “stuck” memories can trigger intense emotional or physical reactions, making us feel as if we’re reliving the past in the present.
Bilateral stimulation is believed to activate the brain’s natural information processing system. This system is responsible for making sense of new experiences, consolidating memories, and integrating them into our existing network of memories. By stimulating both brain hemispheres, bilateral stimulation may help unlock the “stuck” traumatic memory. This allows the brain to reprocess the experience in a safe way, creating a felt sense that the past is in the past.
Reduced Emotional Distress
Bilateral stimulation may activate calming pathways in the brain, reducing the emotional and somatic charge associated with the original stressor or trauma. When a painful memory is combined with enough BLS – within a safe and attuned environment such as EMDR therapy – eventually the brain and body will be able to recall the memory without becoming overwhelmed.
The memory becomes just a memory.
The memory is no longer stored as a fragmented pain capsule; or as a perpetual fight, flight, freeze response in the body. The memory is stored in its proper filing cabinet, in the past, as a memory. The body is able to exhale a sigh of relief.
Here’s what we know about the science of BLS.
Our nervous system has two main branches: the sympathetic nervous system (fight-or-flight) and the parasympathetic nervous system (rest-and-digest). When faced with stress or danger, the sympathetic system kicks in, releasing hormones like adrenaline that increase heart rate, breathing, and blood pressure.
Bilateral stimulation is thought to stimulate the parasympathetic nervous system, essentially hitting the brakes on the fight-or-flight response.
As a disclaimer, bilateral stimulation may not completely erase the distressing emotions associated with a memory. The goal is not to feel nothing. Sadness, anger, and grief all need to be felt and acknowledged, and it’s not helpful to bypass these emotions in the name of healing.
The goal of EMDR therapy is to allow these emotions to move through the nervous system so that distress levels can reduce to a manageable level.
REM Sleep Connection
Bilateral stimulation mimics the rapid eye movements (REM) that occur during sleep. REM sleep is a crucial stage for memory consolidation and emotional processing. By replicating this rhythm, EMDR may facilitate a similar healing process while you’re awake.
Beyond BLS, there’s the whole EMDR experience.
Bilateral stimulation is a powerful technique, but it’s just one piece of the EMDR process. It’s not possible to administer, or self-administer, EMDR through BLS alone.
The EMDR process involves several steps, all of which must occur under the guidance of a trained EMDR therapist.
History-taking & memory selection: We’ll discuss your experiences and identify specific memories to work on.
Resource installation: We’ll explore ways to access neutral and positive experiences in your nervous system – such as through movement and mindfulness practices (Calm Place, Inner Ally, Grounding Tree, Container). This allows you to have an anchor of stability and grounding within yourself, to come back to as needed.
Processing: This is where bilateral stimulation comes in. While focusing on the memory and associated emotions and sensations, you’ll engage in bilateral stimulation techniques. As you process, you may experience shifts in your brain and body. You may notice new and different thoughts. You might feel a sense of emotional release, expansion, or completion.
Integration: After each processing session, we’ll check in. We’ll explore what’s coming up for you and what the next steps are.
EMDR therapy can take place through weekly sessions or through intensive therapy sessions (accelerated and focused healing within a short period of time).
If you’d like to experience EMDR therapy, let’s connect.
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About the Author
I’m Liz Zhou, a holistic trauma therapist (MA, LPCC, she/her). My work integrates teachings from psychology, neurobiology, multicultural awareness, and spirituality. I provide compassionate therapy for highly sensitive people across Colorado.
