What Is Bilateral Stimulation in EMDR?
Bilateral stimulation (BLS) is one of the most unique and essential parts of EMDR (Eye Movement Desensitization and Reprocessing) therapy. While EMDR is widely known as an evidence-based treatment for trauma, anxiety, and other mental health challenges, it's the use of bilateral stimulation that truly sets it apart. This rhythmic, alternating stimulation activates both sides of the brain, helping to unlock the brain’s natural ability to process and heal from distressing experiences.
In this blog, I will explain what bilateral stimulation is, how it’s used in EMDR therapy, and what the research tells us about its role in emotional healing and nervous system regulation.
Understanding EMDR Therapy
EMDR was developed by psychologist Francine Shapiro in the late 1980s. It’s a structured therapy designed to help people heal from trauma and other distressing life experiences. By targeting unprocessed memories that continue to fuel emotional pain, physical symptoms, or deeply rooted negative self-beliefs, EMDR allows the brain to reprocess those experiences in a way that promotes relief, resolution, and lasting change.
EMDR follows a structured eight-phase protocol, with one of its most distinctive elements being bilateral stimulation during the reprocessing phase. This rhythmic left-right stimulation activates the brain’s natural healing mechanisms, helping clients remain grounded in the present while safely accessing and reprocessing painful memories from the past.
Numerous studies support the effectiveness of EMDR. In a meta-analysis by Chen et al. (2014), EMDR was found to significantly reduce PTSD symptoms, with outcomes comparable to and often better than trauma-focused CBT.
What Is Bilateral Stimulation?
Bilateral stimulation involves rhythmic, alternating stimulation of the left and right sides of the body. BLS can be delivered in several ways:
Eye movements: Following the therapist’s fingers as they move side to side, or tracking a visual stimulus on a screen.
Tapping: Alternating taps on arms, thighs, or knees
Auditory tones: Listening to sounds that alternate between the left and right ear through headphones.
Vibration: Holding tactile pulsers or buzzers that vibrate alternately in each hand.
The purpose of BLS is to gently activate both hemispheres of the brain while the client focuses on a distressing memory. This helps the brain reprocess the experience in a way that’s adaptive, manageable, and no longer emotionally overwhelming.
Why the Brain Gets “Stuck” After Trauma
Trauma can overwhelm the brain’s ability to process information, causing it to store the memory in a raw, unprocessed form. This is why certain images, sensations, or emotions can feel just as intense today as they did years ago. The brain hasn’t finished processing the event.
Research shows that EMDR with bilateral stimulation helps shift these distressing memories from a state of emotional reactivity to one of resolution. A randomized controlled trial by van den Hout et al. (2001) found that eye movements during recall significantly reduced the vividness and emotionality of negative memories compared to recall without eye movements.
Learn how EMDR therapy works in the brain
How Bilateral Stimulation Supports Healing
Bilateral stimulation helps the brain reprocess “stuck” traumatic memories by:
Reducing the vividness and emotional charge of distressing images (Lee & Cuijpers, 2013)
Activating both hemispheres of the brain for more integrated processing (Propper & Christman, 2008)
Enhancing a sense of safety and dual awareness (you stay grounded in the present while accessing the past)
Supporting adaptive learning and new insights, often replacing negative beliefs like “I’m not safe” with more empowering ones like “I survived” or “It wasn’t my fault”
What It Feels Like in Session
Many clients describe bilateral stimulation as calming, rhythmic, or even trance-like. During EMDR sessions, I will guide you through short “sets” of stimulation while you bring up a memory to mind. After each set, we’ll pause so you can notice what comes up: images, emotions, thoughts, or body sensations. We’ll then continue with additional sets, allowing your brain to do the work of reprocessing until the memory feels less emotionally charged and more resolved.
As clients progress, they often report:
A “lightness” in their body
Fewer distressing images
Reduced guilt or shame
Increased clarity or insight
A study by Maxfield et al. (2008) showed that eye movements during EMDR significantly increase the speed and effectiveness of desensitization, helping clients reach adaptive conclusions more quickly than recall alone.
Theories Behind How Bilateral Stimulation Works
Although researchers are still exploring exactly how BLS works, several theories have been proposed:
1. Working Memory Taxation
Research by Gunter and Bodner (2008) showed that engaging in a memory while simultaneously performing a competing task can significantly reduce the emotional intensity of that memory.
2. REM Sleep Analogy
Eye movements in EMDR are thought to mimic those that occur during REM sleep, when the brain naturally processes emotional memories. EMDR may tap into this self-healing mechanism. (Stickgold, 2002)
3. Increased Interhemispheric Communication
BLS enhances communication between left and right hemispheres, supporting emotional regulation and memory integration. (Propper & Christman, 2008)
4. Orienting Response
BLS may trigger a neurological “orienting response” that calms the nervous system. It is similar to how we scan our surroundings to feel safe after a threat. (Schubert & Lee, 2009)
Is One Type of Bilateral Stimulation Better?
Eye movements have the strongest research support, but all forms of BLS—tapping, auditory tones, and tactile stimulation are effective. A 2010 study by Barrowcliff et al. found no significant difference in effectiveness between eye movements and alternating tones, suggesting that flexibility in delivery does not reduce EMDR’s healing potential.
In my EMDR sessions, I often use a combination of eye movements, tapping, and auditory tones. These forms of BLS help “tax” the working memory, which research suggests plays a role in reducing the vividness and emotional intensity of distressing memories. This enhances the desensitization process and supports deeper, more efficient reprocessing.
What If It Doesn’t Feel Right?
It’s completely normal for bilateral stimulation to feel unfamiliar at first. Some clients may even worry they’re “doing it wrong.” But you don’t need to try or force anything, just allow the process to unfold. EMDR isn’t about reliving the trauma or thinking harder. It’s about letting your brain do what it already knows how to do: heal.
If something feels off, uncomfortable, or not helpful, let your therapist know. The process can always be adjusted to meet your needs.
Want to Explore EMDR Therapy in Oklahoma City or Dallas?
At Mood Therapy, I offer personalized EMDR therapy for adults navigating trauma, anxiety, or depression. Whether you’re new to therapy or seeking deeper healing, I’m here to help you reconnect with yourself and move forward. I also offer EMDR intensives (Oklahoma and Texas) for those who prefer to make faster progress.
Schedule a Free Consultation to learn how EMDR therapy could support your healing.
References:
Barrowcliff, A. L., Gray, N. S., Freeman, T. C., & MacCulloch, M. J. (2010). Eye movements reduce the vividness, emotional valence, and electrodermal response to negative autobiographical memories. Journal of Forensic Psychiatry & Psychology, 21(4), 523–545.
Chen, Y. R., Hung, K. W., Tsai, J. C., Chu, H., Chung, M. H., Chen, S. R., & Chou, K. R. (2014). Efficacy of eye-movement desensitization and reprocessing for patients with posttraumatic-stress disorder: A meta-analysis of randomized controlled trials. PLOS ONE, 9(8), e103676.
Gunter, R. W., & Bodner, G. E. (2008). How eye movements affect unpleasant memories: Support for a working-memory account. Behaviour Research and Therapy, 46(8), 913–931.
Lee, C. W., & Cuijpers, P. (2013). A meta-analysis of the contribution of eye movements in EMDR therapy: A component analysis. Behaviour Research and Therapy, 51(6), 231–239.
Maxfield, L., Melnyk, W. T., & Hayman, C. A. (2008). A working memory explanation for the effects of eye movements in EMDR. Journal of EMDR Practice and Research, 2(4), 247–261.
Propper, R. E., & Christman, S. D. (2008). Interhemispheric interaction and saccadic horizontal eye movements: Implications for episodic memory, EMDR, and PTSD. Journal of EMDR Practice and Research, 2(4), 269–281.
Schubert, S. J., & Lee, C. W. (2009). Adult PTSD and the efficacy of EMDR: A review of randomized controlled trials. Journal of EMDR Practice and Research, 3(4), 264–269.
Stickgold, R. (2002). EMDR: A putative neurobiological mechanism of action. Journal of Clinical Psychology, 58(1), 61–75.
van den Hout, M., Muris, P., Salemink, E., & Kindt, M. (2001). Autobiographical memories become less vivid and emotional after eye movements. British Journal of Clinical Psychology, 40(2), 121–130.
