What Is Alternating Bilateral Stimulation?

What Is Alternating Bilateral Stimulation?

Short Answer: Alternating bilateral stimulation is a repeated side-to-side pattern used during Eye Movement Desensitization and Reprocessing (EMDR). It can involve moving the eyes from left to right, hearing sounds alternate between the left and right ears, or feeling taps alternate between the left and right sides of the body. During EMDR, this stimulation is used while you briefly focus on a memory, thought, feeling, or body sensation. Researchers are still studying exactly why it contributes to EMDR, but one leading explanation is that doing another attention-demanding task while recalling a memory places demands on working memory and may change how vivid or emotionally intense the memory feels.

Key Takeaways

• Alternating bilateral stimulation means stimulation that shifts repeatedly from one side to the other.
• It can use eye movements, sounds, or touch.
• In EMDR, it is used while you also briefly focus on a memory, thought, feeling, or sensation.
• Alternating bilateral stimulation is one part of EMDR, not the entire treatment process.
• Researchers continue to study exactly why it contributes to EMDR.
• The idea that it works simply by “activating both sides of the brain” is not an established explanation.

What Does “Alternating Bilateral” Mean?

The phrase sounds technical, but it is fairly simple when broken down.

Bilateral means involving two sides.

Alternating means moving back and forth between those sides rather than stimulating both sides at exactly the same time.

So alternating bilateral stimulation might look like:

• Your eyes moving left, then right, then left again.
• A sound playing in your left ear, then your right ear.
• A tap on the left side of your body, followed by a tap on the right.

This side-to-side pattern is commonly used during EMDR. The EMDR International Association describes bilateral stimulation as alternating lateral eye movements and/or alternating auditory or tactile stimulation.

What Types of Alternating Bilateral Stimulation Are Used?

There are several common ways to create the alternating pattern.

Eye Movements

Visual bilateral stimulation typically involves following something that moves from side to side.

For example, you might follow a moving light, dot, or other visual target with your eyes as it travels repeatedly from left to right.

Eye movements are the form most closely associated with EMDR and have received substantial research attention. Studies have found that making eye movements while recalling unpleasant memories can reduce ratings of memory vividness and emotional intensity.

Alternating Sounds

Auditory bilateral stimulation uses sound.

Usually, tones or other sounds alternate between the left and right ears, often through headphones.

You might hear a tone on the left, then the right, followed by the same pattern repeatedly.

Auditory stimulation is used in EMDR, although research suggests it should not automatically be assumed to have exactly the same effects as eye movements. Some experimental studies have found stronger working-memory effects from eye movements than from alternating sounds.

Alternating Tapping

Tactile bilateral stimulation uses touch.

For example, taps may alternate between the left and right hands, knees, shoulders, or another part of the body.

The important feature is the repeating side-to-side pattern.

Tactile stimulation is another recognized form of bilateral stimulation used within EMDR.

How Is Alternating Bilateral Stimulation Used During EMDR?

During the reprocessing parts of EMDR, you usually bring a specific memory, thought, emotion, image, or body sensation to mind.

At the same time, you follow the bilateral stimulation for a short period.

For example, you might:

1. Bring a distressing memory to mind.
2. Follow a moving visual target from side to side for a brief set.
3. Pause.
4. Notice what thoughts, feelings, memories, or sensations come up.
5. Continue with another set.

This means your attention is divided between what you are remembering and what you are doing in the present.

Research often describes this as a dual-attention task because you are attending to both the memory and another task at the same time. EMDR may be used to work with memories and reactions connected to anxiety.

Why Is the Stimulation Alternated From Side to Side?

The alternating pattern is a traditional and recognizable feature of EMDR, but researchers are still studying which parts of that pattern are most important.

One older theory suggested that rapidly alternating left-right stimulation might help by increasing interaction between the two sides of the brain. Some experiments have investigated this possibility.

However, other research has found that tasks do not necessarily need to alternate horizontally to affect memory. Vertical eye movements and other attention-demanding tasks can also produce effects in experimental settings.

These findings have contributed to another major explanation: that the important feature may be the demand the secondary task places on working memory rather than the left-right pattern itself.

So the term bilateral stimulation accurately describes how the stimulation is commonly delivered during EMDR, but researchers have not established that alternating the two sides is the only reason the technique has an effect.

What Does Working Memory Have to Do With It?

Working memory is the limited mental workspace you use to temporarily hold and work with information.

For example, you use working memory when you:

• Keep a phone number in mind long enough to type it.
• Remember the beginning of a sentence while reading the end.
• Hold directions in mind while following them.

Remembering a vivid emotional experience also requires mental resources.

Following moving objects with your eyes or performing another attention-demanding task requires mental resources too.

The working-memory explanation proposes that when you do both at the same time, the two tasks compete for this limited capacity. As a result, the remembered image may temporarily become less vivid or emotionally intense.

A substantial body of experimental research supports working-memory effects as one explanation for the role of eye movements in EMDR, although researchers continue to investigate the full mechanism.

Distressing memories can also be connected with ongoing stress in everyday life.

Does Bilateral Stimulation “Activate Both Sides of the Brain”?

You may see alternating bilateral stimulation explained online as a technique that simply “activates both sides of the brain.”

That description is too definite.

Researchers have studied changes in brain activity and communication associated with eye movements and other forms of stimulation, and theories involving interhemispheric interaction have been proposed. But research has not established that EMDR works simply because the left and right sides of the brain are alternately activated.

The working-memory explanation currently has substantial research support, and other mechanisms have also been proposed.

It is therefore more accurate to say that scientists are still studying exactly how bilateral stimulation contributes to EMDR.

Is Bilateral Stimulation the Same Thing as EMDR?

No.

Bilateral stimulation is one component of EMDR.

EMDR is a structured process that includes several phases. Depending on where you are in the process, it can involve identifying what you want to work on, noticing beliefs and emotions connected with it, using bilateral stimulation, checking what comes up, and continuing through additional processing.

Simply watching something move from side to side or listening to alternating sounds is not the same as completing the full EMDR process.

Alternating Bilateral Stimulation in Self-Guided EMDR

Alternating bilateral stimulation can also be delivered digitally, which makes it possible to use visual or auditory stimulation in online and self-guided EMDR formats.

With the Virtual EMDR self-guided program, for example, bilateral stimulation is built into the online process, and users can select and adjust available stimulation settings themselves.

This is one reason EMDR does not require someone to physically move a hand back and forth in front of you. The alternating stimulus can be produced visually or through sound in an online format as well.

Conclusion

Alternating bilateral stimulation is the repeated side-to-side stimulation used during EMDR. It may involve eye movements, alternating sounds, or alternating taps.

During EMDR, you use this stimulation while briefly focusing on a memory, thought, emotion, or sensation, creating a divided-attention task.

Although the alternating left-right pattern is strongly associated with EMDR, researchers have not established that simply stimulating both sides of the brain explains how it works. One of the leading explanations is that performing another attention-demanding task while recalling a memory places demands on working memory, which may reduce how vivid or emotionally intense the memory feels.

Bilateral stimulation is therefore an important part of EMDR, but it is only one part of the larger EMDR process.