Does Transcutaneous Vagal Nerve Stimulation Improves Fear Extinction in Humans

Study Overview
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Brief Summary
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A recent study with rats showed that electrical stimulation of the vagus nerve (VNS) facilitates extinction of fear (Pena, Engineer, & McIntyre, Biological Psychiatry, 2013). The hypothesized mechanism is that VNS both enhances memory consolidation (by increasing noradrenergic neurotransmission) and reduces anxiety (thus: preventing fear responses to the CS which may re-consolidate the fear memory). The effect was only apparent when VNS occurred during exposure of the fear conditioned stimulus (CS), and not when stimulation was given immediately following exposure. These results may have implications for the treatment of anxiety disorders in humans. However, until recently, the only means to investigate the effects of VNS on human fear learning would have required the invasive implantation of vagus nerve stimulators. This has fortunately changed, as a non-invasive transcutaneous VNS device has been approved for use in the E.U. for the treatment of psychological disorders. This study proposes to use a t-VNS to investigate its effects on fear learning and extinction in (healthy) humans. Previous research has only investigated the effects it has on human mood and memory. The results obtained suggest that it reduces negative affect and enhances memory, findings which are consistent with those reported for rats. It is thus reasonable to expect that t-VNS will facilitate the extinction of fear in humans. The present study aims to answer the following research questions: Does t-VNS during extinction training: accelerates extinction curves reduces spontaneous recovery of previously extinguished fear reduce re-acquisition of fear reduce generalization of fear to other stimuli that resemble the CS+? facilitates the generalization of inhibitory learning to stimuli that resemble the CS-?

Official Title
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Does Transcutaneous Vagal Nerve Stimulation Improves Fear Extinction in Humans

Conditions
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Healthy Adults

Intervention / Treatment
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* Device: t-VNS
* Device: sham stimulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: healthy men and women aged 16 - 50 years Exclusion Criteria: current or past psychiatric or neurological disorder use of psychopharmaca use of medication that affects autonomic nervous functioning (e.g., bèta-blockers) current cardiac or respiratory disorder pregnancy

Ages Eligible for Study
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Minimum Age: 16 Years
Maximum Age: 50 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: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: t-VNS<br>electrical stimulation of the concha of the ear 30sec trains of 0.25msec-duration monophasic square wave pulses at 25Hz, with a stimulation intensity not exceeding 0.5 mA | Device: t-VNS<br>* The device that will be used is approved for systematic use by those with epilepsy and depression in the European Union. It has been used in studies of acute stimulation with healthy participants with no significant changes in heart rate or breathing (Kraus et al., 2007; Busch et al., 2013).<br>* Other names: NEMOS®, Cerbomed, Erlangen, Germany;|
| Sham Comparator: sham t-VNS<br>Sham stimulation of the earlobe will be conducted by positioning the electrode upside down 30sec trains of 0.25msec-duration monophasic square wave pulses at 25Hz, with a stimulation intensity not exceeding 0.5 mA | Device: sham stimulation<br>* electrodes will be put upside down<br>* Other names: NEMOS®, Cerbomed, Erlangen, Germany;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| fear response | startle blink EMG skin conductance response ECG respiration self-reports | 3 test days |