Bilateral stimulation: Differential effects in EEG and peripheral physiology

This study examined the physiological effects of visual and tactile BLS on frontal electroencephalography (EEG) activity and autonomic arousal in patients with PTSD and healthy controls.

Article Abstract

“Background: Bilateral sensory stimulation (BLS), such as eye movements or alternating tactile stimulation, is a key component of Eye Movement Desensitisation and Reprocessing (EMDR), a recommended treatment for post-traumatic stress disorder (PTSD). However, the neurophysiological mechanisms underlying BLS remain poorly understood.

Aims: This study examined the physiological effects of visual and tactile BLS on frontal electroencephalography (EEG) activity and autonomic arousal in patients with PTSD and healthy controls, by varying the type of stimulation in different emotional stimuli.
Method: Twenty female PTSD patients and twenty matched healthy controls participated in a counterbalanced, within-subjects design. Participants recalled a subjectively stressful or neutral event while receiving visual or tactile BLS. Frontal EEG and peripheral psychophysiological measures were recorded before and after stimulation. Data were analysed using mixed model analysis to examine the effects of stimulation type, memory condition and group.
Results: Both visual and tactile BLS significantly increased the total power of frontal EEG and decreased spectral edge frequency and peripheral physiological activation. These effects were consistent between the groups and memory conditions.
Conclusions: BLS, regardless of visual or tactile modality or emotional memory content, is associated with increased frontal EEG activity and reduced autonomic arousal. These findings support the hypothesis that BLS facilitates top-down cortical regulation, potentially aiding emotional processing in EMDR by using an inherent mechanism to promote psychological recovery. More research is needed to clarify the neural mechanisms and clinical implications.”

—Description from publisher

Article Access

Open Access

Single, M., Schäflein, E., Spieler, D., Henn, M., Hanewald, B., & Sack, M. (2025). Bilateral stimulation: Differential effects in EEG and peripheral physiology. British Journal of Psychotherapy Open, 11(6), e278, 1-7. Open access: https://doi.org/10.1192/bjo.2025.10887

About the Journal

“BJPsych Open is a high-quality, online-only open access journal for the publication of all methodologically sound research in psychiatry and disciplines related to mental health.”

—Description from publisher

View the Resource

Date
November 13, 2025

Creator(s)
Markus Stingl, Eva Schäflein, Derek Spieler

Contributor(s)
Martina Henn , Bernd Hanewald, Martin Sack

Topics
PTSD

Practice & Methods
BLS, Mechanisms of Action, Neurobiology

Publisher
Cambridge University Press

Rights
Copyright © The Author(s), 2025. Published by Cambridge University Press on behalf of the Royal College of Psychiatrists. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.

APA Citation
Single, M., Schäflein, E., Spieler, D., Henn, M., Hanewald, B., & Sack, M. (2025). Bilateral stimulation: Differential effects in EEG and peripheral physiology. British Journal of Psychotherapy Open, 11(6), e278, 1-7. Open access: https://doi.org/10.1192/bjo.2025.10887

Audience
EMDR Therapists, Other Mental Health Professionals

Language
English

Content Type
Article, Peer-Reviewed

Access Type
External Resource, Open Access

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