Neural Mechanisms of Imaginal and in Vivo Exposure

Study Overview
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Brief Summary
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Imaginal exposure is a widely used and effective psychological treatment technique. Recent research suggests that neural activations and emotional responses during imaginal exposure are similar to those elicited during in vivo exposure. However, to the investigators knowledge, no direct comparison between in vivo and imaginal exposure has been performed during neuroimaging. This study compares neural activations and emotional responses during imaginal and in vivo exposure. This study also explores the generalizability of fear reduction achieved through imaginal exposure to fear responses elicited by in vivo stimuli, and vice versa, in a follow-up session approximately one week later. A better understanding of the mechanisms behind both types of exposure could have significant clinical utility, as well as elucidate the differences between fear created from outward stimuli and fear created from inward stimuli, such as mental imagery.

Detailed Description
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The study includes participants fearful of spiders and entails two experimental sessions, roughly one week apart. The first session includes brain imaging using functional magnetic resonance imaging (fMRI). During the first session, participants will be randomized into one of two conditions - in vivo exposure or imaginal exposure. In the in vivo exposure condition, participants will be shown video clips of spiders (fearful stimuli) and leaves (neutral stimuli) in different situations. In the imaginal exposure condition, participants will be instructed to produce mental imagery of the corresponding stimuli used for in vivo exposure. Previous research found that the brief exposure procedure used during session 1 produced a fear reduction when the procedure was repeated one week later. Thus, in order to conceptually replicate this finding, and to examine the generalizability of fear reduction, participants return roughly one week later for a follow-up session. In the follow-up session, participants undergo a similar exposure procedure as used in session 1, but with half of the stimuli in vivo and the other half of the stimuli as mental imagery. In this way, it can be studied whether fear reduction generalize from exposure modality to another. The effects of imaginal and in vivo exposure on avoidance behavior towards fear-provoking stimuli (spiders) will also be assessed using an approach-avoidance conflict paradigm, using pictures of spiders to probe spider fear. The current study will also explore the impact of mental imagery vividness during imaginal exposure on fear reduction. Additionally, the study will assess if vividness level can predict the generalizability of the effects of imaginal exposure to fear-provoking stimuli (mental imagery of a spider) on subsequent fear responses to to in vivo stimuli (film clip of a spider) one week later. Functional magnetic resonance imaging (7T) is used to measure neural activations (session 1). Skin conductance is used to measure arousal response (session 1 & 2). Subjective fear and mental imagery vividness ratings will also be collected.

Official Title
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Neural Mechanisms of Imaginal and in Vivo Exposure: Exploring the Differences Between Imaginal and in Vivo Exposure, Using fMRI and Psychophysiology

Conditions
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Fear of Spiders

Intervention / Treatment
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* Behavioral: Imaginal exposure
* Behavioral: Exposure
* Behavioral: Approach-avoidance conflict
* Behavioral: In vivo exposure


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Willing and able to provide informed consent and complete study procedures Fear of spiders Exclusion Criteria: Current psychiatric disorder other than spider phobia Current use of psychotropic medication Current neurological conditions MRI-contraindications (i.e metal implants in skull)

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Imaginal exposure<br>Exposure to mental imagery including a fearful stimulus (spider) and corresponding scenes including a neutral stimulus (leaf) | Behavioral: Imaginal exposure<br>* Session 1 (Day 1): Participants receive repeated exposure to mental imagery of fear-provoking stimuli (spiders) and neutral stimuli (leaves) while undergoing brain imaging med fMRI.<br>Behavioral: Exposure<br>* Session 2 (Ca one week): Participants receive both imaginal and in vivo exposure to fear-provoking stimuli and neutral stimuli (both arms are exposed to both video clips (in vivo exposure) and mental imagery (imaginal exposure). Session 2 is conducted in the laboratory, i.e., no brain imaging.<br>Behavioral: Approach-avoidance conflict<br>* Session 2 (Ca one week): Spider fear is probed by an approach-avoidance conflict task. Participants can receive varying small rewards for watching pictures of spiders, or avoid the spider pictures at the cost of not receiving a reward (neutral pictures are shown instead).<br>|
| Experimental: In vivo exposure<br>Exposure to video clips including a fearful stimulus (spider) and corresponding clips including a neutral stimulus (leaf) | Behavioral: Exposure<br>* Session 2 (Ca one week): Participants receive both imaginal and in vivo exposure to fear-provoking stimuli and neutral stimuli (both arms are exposed to both video clips (in vivo exposure) and mental imagery (imaginal exposure). Session 2 is conducted in the laboratory, i.e., no brain imaging.<br>Behavioral: Approach-avoidance conflict<br>* Session 2 (Ca one week): Spider fear is probed by an approach-avoidance conflict task. Participants can receive varying small rewards for watching pictures of spiders, or avoid the spider pictures at the cost of not receiving a reward (neutral pictures are shown instead).<br>Behavioral: In vivo exposure<br>* Session 1 (Day 1): in vivo exposure. Participants receive repeated exposure to film clips of fear-provoking stimuli (spiders) and neutral stimuli (leaves) while undergoing brain imaging med fMRI.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Blood oxygen level dependent contrast (BOLD-signal) during exposure to fearful stimuli (in vivo or imaginal). | BOLD-signal is assessed using functional magnetic resonance imaging. | Day 1 | 
| Physiological arousal response during exposure (in vivo or imaginal). | Skin-conductance responses are used as a measure of physiological arousal response, i.e. event-related rise in electrodermal activity as a response to stimulus. Unit of measure is microSiemens. | Day 1 | 
| Physiological arousal response during follow-up exposure | Skin-conductance responses are used as a measure of physiological arousal response, i.e. event-related rise in electrodermal activity as a response to stimulus. Unit of measure is microSiemens. | One week after Day 1 | 
| Ratings of subjective fear experienced during exposure to fearful stimuli and neutral stimuli | Scale 0-100; no fear at all - extreme fear | Day1 | 
| Ratings of subjective fear experienced during exposure to fearful stimuli and neutral stimuli | Scale 0-100; no fear at all - extreme fear | One week after Day 1 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Ratings of subjective fear participants expect to experience during exposure to fearful stimuli | Scale 0-100; no fear at all - extreme fear | Day 1 & one week after Day 1 | 
| Number of approach-avoidance decisions during an approach-avoidance behaviour task using fearful stimuli (spiders) | Number of participants' decisions to avoid looking at a fearful stimuli, or to look at them and be compensated with at small amount. | One week after Day 1 | 
| Task-specific mental imagery vividness ratings to fearful and neutral stimuli during imaginal exposure, and follow-up exposure (not applicable during in vivo exposure). | Vividness of Imagery (scale: 1-5; no image at all - image as clear and vivid as real life) | Day 1 & one week after Day 1 | 
| Spielberger State-Trait Anxiety Inventory (STAI-T) | STAI-T is a self-rated questionnaire which assess trait anxiety. Scale: 20-80 in the participants where higher scores represent higher levels of trait anxiety | One week after Day 1 | 
| Vividness of visual imagery Questionnaire (VVIQ) | VVIQ is used to measure individual differences in Vividness of Visual mental Imagery; scale: 16-80 where higher scores represent a higher ability for visual imagery. | One week after Day 1 | 
| Amount of watching film clips (not applicable during imaginal exposure). | Assessment of avoidance when watching film clips. To what extent did you watch the film clips (i.e. not close your eyes)? Scale 0-100% of film clips. | Day 1 & one week after Day 1 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Imaginal exposure, Exposure, Mental Imagery