Neural Basis of the Effect of EMDR Therapy

Summary

This study aimed to investigate the effects of a single session of Butterfly Tapping (BT), a self-administered form of alternating bilateral stimulation, on emotional reactivity and its neurophysiological correlates. 46 participants will be randomly assigned to an experimental (Exp) or control (Con) group. The Exp group performed a 15-minute session of BT. Emotional reactivity was assessed before and after the stimulation using a detection task with emotional visual stimuli, presented during electroencephalographic (EEG) recording. EEG analyses were conducted using the event-related potential (ERP) method, specifically focusing on the differential amplitude (negative minus neutral) of the Late Positive Potential (LPP), a centro-parietal component associated with sustained processing of emotionally salient stimuli. Results revealed a significant LPP reduction in the Exp group at T1 compared to T0, whereas no change emerged in the Con group. The topographical distribution of the modulation was predominantly central, consistent with models implicating the LPP in higher-order integrative and evaluative processes. These findings provide preliminary neurophysiological evidence that BT may reduce cortical reactivity to negative emotional stimuli in young clinical populations, supporting its potential as a simple and accessible strategy capable of modulating affective responsiveness.

Conditions

• PTSD - Post Traumatic Stress Disorder

Interventions

BEHAVIORAL

Butterfly Tapping (BT)

Participants adopted the traditional butterfly hug posture: arms crossed over the chest, fingertips placed below the clavicles. They delivered alternating left-right rhythmic taps (\~1 Hz) on their shoulders. Eyes remained closed, and participants were instructed to keep the emotional content active by mentally recalling previously viewed negative images, ensuring sustained affective engagement. Duration: 15 minutes, structured in four blocks of 3 minutes with short pauses. No auditory pacing was provided to preserve spontaneous rhythmicity. Targeted Mechanism Bilateral tactile stimulation aiming to modulate cortico-limbic processing, interhemispheric communication, and sustained emotional reactivity, as indexed by LPP amplitude during ta emotional simple response task

BEHAVIORAL

No intervention control

Participants will adopt the same butterfly-hug position, with arms crossed and hands placed on the chest. No rhythmic tapping or movements will be performed. Eyes are closed for the entire session, as in the experimental arm. Participants will held the emotional images in mind just as in the experimental arm. Duration: 15 minutes, identical block structure and timing as the BT condition. Targeted Mechanism Serves as a posture-matched and expectancy-matched control, ruling out effects of: simple stillness, emotional recall, attentional focus, physical posture, general relaxation effects.

Sponsors & Collaborators

• University of Rome Foro Italico

  lead OTHER

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

NONE

Model

PARALLEL

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2025-01-08

Primary Completion

2025-07-30

Completion

2026-03-15

Countries

• Italy

Study Locations