The role of emotional arousal in Eye Movement Desensitization and Reprocessing (EMDR). Part II: the effects yohimbine on the plasticity of emotionally neutral episodic memories.

Eye Movement Desensitization and Reprocessing (EMDR) is a widely used,
effective psychological treatment for posttraumatic stress disorder (PTSD). Its
core intervention is that patients recall trauma memories while simultaneously
making lateral eye movements. It is largely unknown how EMDR works, however,
much evidence has been obtained for the working memory hypothesis. This
hypothesis comprises that both recalling traumatic memories and making eye
movements (EM) tax working memory (WM), which has limited capacity.
Simultaneously performing both tasks leads to a competition for WM, rendering
the traumatic memories less vivid and emotional. When memories are recollected
they reenter a labile state and become malleable and, because of this, the
traumatic memory is overwritten by the memory that is blurred by EM.

Emotional material is better (re) consolidated than emotional neutral material,
i.e., it is prioritized and is (re) consolidated more vividly and in greater
detail. This is caused by emotional arousal and the accompanying release of
noradrenaline (NA) in the brain. In EMDR emotional material is recollected and
reconsolidated. Therefore, it is expected that emotional arousal is experienced
and NA is released. EMDR might work because despite emotional arousal or
becáuse of this arousal i.e., emotional arousal enhances the reconsolidation of
the blúrred emotional memories.

The primary goal of the present research proposal is to investigate whether
emotional arousal plays a role in the effectiveness of EMDR therapy.

Recent studies by our group have shown that vivid, emotionally neutral memories
cannot be blurred by EM. In the present study we seek to find out whether the
stimulation of arousal by yohimbine during the retrieval of neutral memories
leads the common EMDR effects as observed for emotional memories (reduced
vividness/emotionality)

The proposed study will use a double-blind, placebo-controlled, experimental,
repeated measures design, with medication group (placebo, yohimbine) as
between-subjects independent variable, condition (recall + EM, recall only, no
recall) and time (pretest, posttest, followup)
as within-subjects independent variables, and VAS-rated vividness and
phenomenological qualities of the memory (as measured with the short form for
Memory Experiences Questionnaire* MEQSF) as dependent variables.

Half of the participants will receive 20 mg of the alpha-adrenergic receptor
antagonist yohimbine and half will receive a placebo. Of the three
memories participants have to retrieve during the pretest (and are scored on a
VAS/MEQ-SF), one will be recalled while making EM (recall + EM), one without EM
(recall only), and one will not be retrieved (no recall) during the
intervention. During the posttest and the follow-up all three memories will be
retrieved again and scored on vividness and the MEQ-SF.

This project encompasses a low risk study. The low dosage (20 mg) of yohimbine
has minimal side-effects (see IB for an overview), and serious adverse events
are very unlikely. Participants are carefully screened for contraindicative
conditions and medication use. Another burden for the subjects is that they
have to invest some time (approximately 3 hours) in participating in the study.
The burdens of the test can be justified by the clinical and scientific
relevance of the study. Skin conductance and heart rate measures are
non-invasive. Participants can withdraw at any time from the study.