When you've had a traumatic experience, it sometimes feels as if the painful memory is stuck in your head. Certain triggers can then suddenly bring back all the feelings from that time – as if you were reliving the horror. This brain reaction is normal in itself, but can be very stressful for those affected. The good news: There is a method in psychotherapy that can reduce the intensity of such "stuck" memories. This technique is called bilateral stimulation – which means reciprocal stimulation of both sides. Here, both halves of the body or senses are stimulated alternately, for example, through right-left movements of the eyes, gently alternating tapping the hands, or alternating sounds in the ears. This activates both halves of the brain alternately. In this article, we explain in a sensitive and understandable way why this bilateral stimulation can have a therapeutic effect in processing trauma.
What is bilateral stimulation?
Bilateral stimulation involves rhythmic stimuli that are applied alternately to the left and right. These can be visual (with the eyes), tactile (through touch), or auditory (through sounds). In a typical therapy session, for example, the person follows the therapist's hand movements back and forth with their eyes, or light touches (e.g., on the knee or back of the hand) are applied alternately to the left and right. Sounds can also be used, which are heard alternately in the left and right ear. The important principle is: left-right-left-right, in a steady rhythm. This method is used particularly in certain trauma therapy procedures to help the brain process stressful memories. The underlyingidea is that by alternately activating both sides of the brain, emotional blockages can be released. The pain of the memory is supposedly digested and integrated into the overall memory, so that it loses its horror.
Why can bilateral stimulation help with trauma?
Various scientific approaches attempt to explain why bilateral (reciprocal) stimulation has such positive effects on traumatic memories. Several mechanisms likely play a role. Here are some of the most important theories and findings on how this method works in the brain – illustrated by simple comparisons:
- Divided attention defuses the memory: When we remember something bad, all of our mental resources are often focused on that image—no wonder we're overwhelmed by it. Bilateral stimulation, however, forces the brain to pay attention to two things at once: the memory and the external stimulus. This "multitasking" taxes working memory and leaves less capacity to feel the full impact of the stressful images. Imagine trying to watch a movie through binoculars while constantly panning them back and forth—the image blurs. Likewise, traumatic imagery can lose vividness and emotional power when the brain is distracted. In fact, studies have shown that simultaneous eye movements can significantly reduce the vivid details and emotional intensity of negative memories. The brain then processes the memory more as something from the past and less as a present threat.
- Rhythm like in dream sleep (REM phase): During REM sleep, our eyes move rapidly back and forth. During this sleep phase, the brain processes experiences and sorts memories – especially emotional impressions. Experts suspect that bilateral stimulation mimics this natural mechanism. The alternating stimuli could signal to the brain: You are safe, you can now "clean up" in peace. Neuroscientific research supports this idea. A study on mice showed that alternating visual stimulation (similar to eye movements) activates certain brain regions, which in turn inhibit the amygdala – the part of the brain responsible for fear and alertness. Put simply: In the experiment, the left-right stimulus acted like a calming signal to the fear center. The eye movements during a therapeutic session could therefore have a comparable effect and help the brain process the trauma in a similar way to how it tries to process it every night during dream sleep. Many therapists actually report that patients often sleep better and have fewer nightmares after successful treatment – which indicates that internal processing has started again.
- Safety signal and physical calming: The gentle, predictable stimuli on the left and right can also have a direct calming effect on the body. They remind the brain to stay in the here and now. During a traumatic memory, one often feels internally as if one were in danger again – palpitations, tension, and startle reactions can occur. The rhythmic stimulation then acts like a metronome for the mind: It sets a beat that anchors part of the attention in the safe present moment. Many affected individuals describe feeling guided and less helpless by the steady back and forth – similar to how the monotonous ticking of a clock or swinging in a hammock can be calming. For example, a scientific study showed that bilateral stimulation using alternating touch reduced the physical startle response (the startle reflex) when negative images were present. At the same time, skin conductance – a sign of emotional processing – increased when positive images were present. This suggests that the method can bring the body out of its rigid alarm mode and even promote more positive emotional reactions. The message to the brain is essentially: Look, you're experiencing something right now—but nothing bad is going to happen to you now. You can let go of the fear.
- Both hemispheres of the brain are working together again: Some explanations emphasize that traumatic experiences are processed unequally to some extent – put simply, the right hemisphere (emotional, visual) is left with the horror, while the left (linguistic, analytical) was unable to properly classify the events. Bilateral stimulation is intended to help build a bridge between emotion and reason. By alternately activating both hemispheres, the brain can reconnect the fragmented memory. You could imagine it like this: The information from the traumatic situation is scattered in two spaces – left and right. The reciprocal stimulus opens the door between the spaces, allowing the impressions to reconnect and be integrated into the overall memory. As a result, the memory loses its overwhelming character and becomes a memory like any other, one that may be sad or painful, but no longer completely derails the memory. This reintegration of the memory is a sign of neuroplasticity – the brain learns to form new, less stressful connections. Many therapists observe that after successful bilateral stimulation, patients suddenly develop new thoughts or meanings about the traumatic event (e.g., "I survived and I am strong" instead of "I am helpless"). This indicates that the brain is re-storing the experience—with less fear and more understanding that it is over.
What does science say about the results?
The effectiveness of bilateral stimulation in trauma therapy has been researched for several decades. It is now considered evidence-based, meaning there are numerous studies and clinical experiences that demonstrate its benefits. Its use is particularly well-known in post-traumatic stress disorder, where this method is embedded in a comprehensive therapy form (described here without naming the names). Meta-analyses – studies that evaluate many studies together – conclude that incorporating the bilateral stimulation component has an additional positive effect. For example, one review showed that in therapies with bilateral stimulation, patients' PTSD symptoms and subjective distress were reduced more than in comparable treatments without this component. Laboratory studies with volunteers have also consistently found that memories are less vivid and distressing when eye movements or similar dual tasks are performed during recollection. In other words, the healing effect comes not only from talking about them or time, but also from the left-right stimulation. This is also supported by brain scan studies which observe that certain activity patterns in the brain change under bilateral stimulation – for example, the hyperarousal center calms down and frontal brain areas (responsible for evaluation and control) are activated.
It's important to note that bilateral stimulation doesn't erase the distressing memory—but it does change how we can live with it. Therapy reports show that many sufferers say after completing treatment: "The memory feels distant, as if I have distanced myself from it. I know it happened, but it no longer overwhelms me." Nightmares and flashbacks often decrease, and overall mood and daily functioning improve. A scientific review concludes that by working through their traumatic memories with bilateral stimulation, those affected exhibit fewer symptoms of depression and anxiety and are better able to cope with stress. Such results are encouraging—they show that even deep-seated traumas don't have to remain a lifelong "judgment," but that healing is possible.
Conclusion: Help for the brain to heal itself
In summary, bilateral stimulation helps the brain to catch up on something that was not fully achieved during the traumatic experience: to store the memory meaningfully without it constantly triggering alarms.
For traumatized people, this method can be liberating. It may sound strange at first: How on earth can simple bilateral stimulation reduce my anxiety? But as we've seen, there's a lot of science behind it. Our brain is an amazing organ capable of self-regulation with the right nudges. Bilateral stimulation provides precisely this nudge—it synchronizes, calms, and reconnects different brain areas that had been thrown out of sync by the trauma. And it does this in a gentle way: You don't have to relive everything to process it; instead, your brain does much of the work behind the scenes while you focus on the rhythm.
If you or someone you know is suffering from the aftereffects of a trauma, it can be hopeful to know that such innovative treatment options exist. Bilateral stimulation isn't just hocus-pocus, but a well-researched tool that has helped many people tame the power of their fearful memories. Our brains want to heal—sometimes all it takes is a little nudge from both sides to get there. With patience, support, and the right methods, it's possible that the tormenting, returning film in your head will eventually become just a faint memory—one you can live with and move on.
