The “What” and “Why” of bilateral stimulation in therapy.

By Chantel Bryson, LPCC, CMHC

     Perhaps you’ve heard the term “bilateral stimulation” before or maybe the term is completely new to you; regardless, you are likely to experience this technique if you seek therapy for PTSD, trauma, or other stuck thoughts, emotions, or beliefs. Some of the most effective and thoroughly-researched therapeutic practices for trauma use bilateral stimulation: EMDR and ART. However, when first instructed by your therapist in performing bilateral stimulation, you might feel curious or even cautious about why a such a seemingly odd technique is used in therapy. So let’s talk about what bilateral stimulation is and what it may be doing to enhance your treatment.

     Bilateral stimulation can be conducted using eye-movements, tapping, other body movements, hand-held buzzers, or even sounds. For example, a client might be instructed to follow a therapist’s hand with their eyes in a rhythmic left-to-right or diagonal motion. Or perhaps instead of the therapist’s hand, the client might be moving their eyes to follow a dot on a screen, or a moving light on a lightbar.

     Sometimes eye-movements are uncomfortable for a client or there are other reasons a therapist might choose to implement bilateral stimulation in a different way. In these cases, a therapist might have vibration tools that a client will hold in each hand that produce a gentle, alternating vibration. Often called “buzzers” these tools are becoming a standard piece of equipment in many therapists’ offices. Another popular method is to teach clients how to tap on alternating left and right shoulders or knees. Creative means of performing bilateral stimulation include rocking side-to-side or using headphones to listen to a tone shifting between right and left ears.

     So what does all of this have to do with therapy? Why has bilateral stimulation become an important part of processing trauma and other formative experiences? I’ve had the experience of EMDR therapy coming up in a social setting as a topic of conversation and observing as people unfamiliar with the technique express sentiments ranging from curiosity to skepticism to scorn about bilateral stimulation. One popular snipe regarding the role of bilateral stimulation in EMDR is, “It’s just cognitive therapy with extra steps.” That said, negative sentiments inevitably tend to shift once a few individuals enthusiastically share their personal healing experiences with EMDR therapy utilzing bilateral stimulation. In some cases, individuals are experiencing rapid healing and profound reduction in symptoms after a few sessions of EMDR or ART in a way they have not previously experienced in talk-therapy.

     Therapists use bilateral stimulation during certain trauma-therapy modalities because when bilateral stimulation is applied during the recollection of a traumatic experience (as prompted in a session with a trained therapist), the vividness and emotionality of the trauma memory decreases. Scientists have studied why this effect occurs, and while we don’t have definitive answers, we now have some strong hypotheses that are gaining ground in research.

     One hypothesis is that performing bilateral stimulation while also recalling a difficult experience simply makes your brain work harder. Doing two things at once taxes your working memory which then impacts the brain’s retrieval of the memory, resulting in the memory being only partially retrieved. Partial retrieval is what causes the emotional vividness and traumatic content to become blurred and diminished. Hypothetically, when the memory is stored away again, it is stored as the less vivid version, thereby reducing symptoms that used to come up when a person thought about the memory: panic, hypervigilance, nightmares, etc (Wadji et. al 2022). And, this reduction in vividness occurs without reducing the factual memory of the event; indeed, some studies suggest that factual recall may actually improve with the use of bilateral stimulation (Nieuwenhuis et. al 2013).

     Another recent study found that bilateral stimulation may increase activity in the thinking part of the brain while decreasing the body’s stress response. So, bilateral stimulation appears to reduce fight-or-flight reactions while allowing the thinking part of the brain to help calm and regulate emotional reactions. With this extra boost, people are able to process emotional memories more effectively (Stingle et. al 2025).

     Scientists have even more ideas about why bilateral stimulation works. Some believe that bilateral stimulation mimics the rapid-eye movements seen in REM sleep while we’re dreaming, inducing a similar processing effect in the brain. Others believe that bilateral stimulation causes an orienting and relaxation response in the brain which allows individuals to face their challenging memories without having to suppress or avoid the distress they typically feel when thinking about the memory (Pagnani et. al 2017).

     Ultimately, the mechanisms by which bilateral stimulation works are still a matter of rigorous debate and study. As I’ve worked with clients and also personally experienced therapy modalities such as EMDR and ART, I’ve both observed and felt how bilateral stimulation shifts the vividness of painful memories. I love doing this type of work with my clients because I get to see healing occur in real time. If you are wondering if you might benefit from a therapeutic modality that uses bilateral stimulation, please reach out and let’s talk. *

Nieuwenhuis S, Elzinga BM, Ras PH, Berends F, Duijs P, Samara Z, Slagter HA.

Bilateral saccadic eye movements and tactile stimulation, but not auditory stimulation, enhance memory retrieval.

Brain and Cognition, Volume 81, Issue 1, 2013, Pages 52-56, ISSN 0278-2626,

https://doi.org/10.1016/j.bandc.2012.10.003.

Pagani M, Amann BL, Landin-Romero R, Carletto S. Eye Movement Desensitization and Reprocessing and Slow Wave Sleep: A Putative Mechanism of Action. Front Psychol. 2017 Nov 7;8:1935. doi: 10.3389/fpsyg.2017.01935. PMID: 29163309; PMCID: PMC5681964.

Stingl M, Schäflein E, Spieler D, Henn M, Hanewald B, Sack M. Bilateral stimulation: differential effects in EEG and peripheral physiology. BJPsych Open. 2025;11(6):e278. doi:10.1192/bjo.2025.10887

Wadji, D.L., Martin-Soelch, C. & Camos, V. Can working memory account for EMDR efficacy in PTSD?. BMC Psychol 10, 245 (2022). https://doi.org/10.1186/s40359-022-00951-0

*Please reach out to a licensed professional to work through trauma using bilateral stimulation. It is extremely important to be appropriately screened prior to initiating any trauma treatment technique utilizing bilateral stimulation.