How Bilateral Stimulation Impacts Your Nervous System (and Why It Can Sometimes Trigger You)

Written By Jamie Gibbs

Bilateral stimulation (BLS) is a core element of EMDR therapy and one of the most powerful tools we have for healing trauma, anxiety, and nervous system dysregulation.
But like all trauma therapies, BLS is not neutral.

For many clients, it is grounding, calming, and transformative.
For others—especially those with complex trauma, dissociation, or unresolved attachment wounds—BLS can feel activating or even triggering at first.

This doesn’t mean something is wrong with you.
It means your nervous system is responding exactly the way it was shaped to respond.

This blog explains:

  • What BLS is

  • How it regulates the nervous system

  • Why it can also trigger activation

  • How to use it safely

  • What to expect in EMDR or trauma-informed therapy

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What Is Bilateral Stimulation?

Bilateral stimulation involves rhythmic, alternating stimulation of the left and right sides of the body or brain. Examples include:

  • Eye movements

  • Alternating tapping

  • Buzzers in each hand

  • Left/right auditory tones

  • Rhythmic walking or rocking (natural BLS)

In EMDR, BLS is used deliberately to help the brain reprocess traumatic material safely and efficiently.

How Bilateral Stimulation Regulates the Nervous System

1. It reduces amygdala activation

The amygdala is the brain’s alarm system. BLS helps it calm down, signaling that the threat has passed.

2. It supports integration between brain hemispheres

Trauma is often stored as images, sensations, and emotions without narrative. BLS allows the thinking brain to join the trauma brain so real integration can happen.

3. It shifts the system out of fight/flight or shutdown

By switching activation between hemispheres, the brain is reminded it’s no longer frozen in survival mode.

4. It supports emotional processing

Clients often notice memories losing intensity, new insights emerging, and a sense of clarity replacing confusion or reactivity.

But Here’s the Part Most People Don’t Talk About: BLS Can Sometimes Be Triggering

Bilateral stimulation moves energy, memory, sensation, and emotion through the system.

For some clients, this is relieving.
For others—especially early on—it can feel like:

  • A wave of emotion

  • A surge of anxiety

  • Flashbacks

  • Body sensations resurfacing

  • Dissociation

  • Nausea or dizziness

  • Feeling “too much,” “too fast,” or “too exposed”

This is not a mistake.
This is your nervous system opening the door to trauma material that has been stored, suppressed, or compartmentalized.

Let’s break down why this happens.

Why Bilateral Stimulation Can Feel Triggering

1. It accesses memory networks that were previously walled off

Trauma is often stored as fragments:

  • Body sensations

  • Images

  • Emotions

  • Belief states

  • Smells, sounds, or flashes

BLS awakens these networks so they can be processed.
But because trauma is implicit, your body may respond before your mind understands what’s happening.

2. It lowers defenses that previously kept you “functionally fine”

Protectors like:

  • Numbing

  • Avoidance

  • Perfectionism

  • Overthinking

  • Shutdown

  • Hyper-independence

  • Dissociation

worked hard to keep pain below the surface.

BLS temporarily softens these protectors, which can feel like “losing control.”

3. It moves stuck energy through the body

Many clients feel:

  • Tingling

  • Heat

  • Tightness

  • Shaking

  • Pressure in chest or throat

  • Gut discomfort

This is the body finally releasing something it has carried for years.

This can feel triggering because your system is not used to allowing emotional or somatic movement.

4. If the Window of Tolerance is narrow, activation happens quickly

For clients with complex trauma, childhood wounds, or attachment injuries, the nervous system may:

  • Flood

  • Shut down

  • Oscillate rapidly between sympathetic and dorsal vagal states

  • Lose grounding

This is why skilled pacing, resourcing, and titration are essential.

5. BLS can connect current triggers to old wounds

If something happening in your life mirrors an old trauma, BLS may surface that connection.

This isn’t retraumatization—
It’s the beginning of reconnection, integration, and resolution.

Triggering Is Not a Sign You’re Doing EMDR Wrong

It’s actually a sign the brain is:

  • Opening old memory networks

  • De-freezing traumatic material

  • Connecting past and present

  • Preparing for integration

Good EMDR and trauma-informed therapy is not about “pushing through.”
It’s about pacing, titration, containment, and strengthening the observing-self so that this material becomes tolerable—not overwhelming.

How We Use Bilateral Stimulation Safely in Therapy

As a trauma-informed clinician, I always ensure:

  • You have grounding resources first

  • Your system is stable enough for deeper work

  • We build capacity slowly, not forcefully

  • I track your activation and adjust pacing moment by moment

  • We use dual awareness so you remain anchored in the present

  • We respect your nervous system’s boundaries

If BLS becomes activating, we:

  • Slow down

  • Switch to taps instead of eye movements

  • Use shorter sets

  • Stop and ground

  • Strengthen your window of tolerance

  • Resource before returning to processing

Your nervous system sets the pace—
not the protocol.

When You Should Tell Your Therapist BLS Is Triggering

Let your therapist know if you feel:

  • Dizzy or spaced out

  • Numb or disconnected

  • Flooded with emotion

  • Stuck in a memory

  • Overwhelmed

  • Shut down

  • Unsafe

  • Confused about what’s happening

This information helps us attune more deeply and adjust the process so you feel supported, safe, and regulated.

Bottom Line: Bilateral Stimulation Is Powerful—And That’s Why It Must Be Used Carefully

When guided safely, BLS helps you:

  • Process trauma

  • Reduce triggers

  • Regulate emotions

  • Resolve past wounds

  • Build secure attachment with yourself

  • Strengthen nervous system resilience

But it’s not a casual tool.

It’s a trauma-processing mechanism, and your system deserves respect, pacing, and attuned support.

Curious Whether EMDR or Bilateral Stimulation Is Right for You?

If you’re wondering how BLS might impact your nervous system, or whether EMDR would help with trauma, anxiety, betrayal trauma, or attachment wounds, I’d love to talk with you.

✨ I offer a free 15-minute consultation.

This is a safe space to ask questions, explore your symptoms, and determine whether this approach is a good fit.

Your brain is designed to heal—sometimes it just needs a guide who understands your system.

Jamie Gibbs
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