Understanding the Effects of Transauricular Vagus Nerve Stimulationon on Neural Networks and Autonomic Nervous System

Study Overview
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Brief Summary
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This trial aims to perform an exploratory, mechanistic, randomized double-blind sham-control trial in healthy participants to assess the physiologic effects of a single 60 minutes session of bilateral taVNS, on neural networks and autonomic function.

Detailed Description
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Several studies have shown promising results of taVNS to treat various disorders such as depression, anxiety, Alzheimer's disease, headache, obesity, and diabetes. However, no mechanistic studies have investigated the taVNS neural network and autonomic nervous system effects of this technique. Therefore, we aim to assess how taVNS can affect EEG metrics and HRV and assess its safety. Also, we aim to evaluate predictors that can influence the response to taVNS, so understanding the variables associated with response to taVNS can help the design of future clinical trials to maximize the effects of this intervention.

Official Title
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Understanding the Effects of Non-invasive Transauricular Vagus Nerve Stimulation (taVNS) on Neural Networks and Autonomic Nervous System: a Randomized Double-blind Sham-control Mechanistic Trial in Healthy Participants

Conditions
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Healthy Volunteers

Intervention / Treatment
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* Device: Transauricular vagus nerve stimulation (taVNS)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Able to provide informed consent to participate in the study. Subject is older than 18 years. Subjects should be naive to the stimulation (taVNS) Exclusion Criteria: Pregnancy. Subjects who have had a neuropsychiatric or a cardiac disorder diagnosis and have received treatment and chronic medication in the past six months, or who have functional deficits as a result. History of alcohol or drug abuse within the past 6 months as self-reported. Presence of the following contraindication to transauricular vagus nerve stimulation Ferromagnetic metal in the head and in the cranium (e.g., plates or pins, bullets, shrapnel) Implanted cranial electronic medical devices (e.g., cochlear implants) Implanted cardiac devices (e.g., pacemaker) Unstable medical conditions (e.g. uncontrolled diabetes, uncompensated cardiac issues, heart failure, or chronic obstructive pulmonary disease). Uncontrolled epilepsy, as defined by previous clinical seizures in the past 3 months in patients with treatment for epilepsy. Suffering from severe depression (as defined by a score of >30 in the Beck Depression Inventory).

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 99 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: Other
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Active taVNS<br>TaVNS will be administered by an earset, with conductive eartips placed on the auricular concha of the ears, connected to a stimulator, and during active stimulation, we stimulate both the cymba conchae and external auditory canal of both left and right ears with the following parameters: 30Hz, 200-250 us, and with adjustable intensity for 60 min. | Device: Transauricular vagus nerve stimulation (taVNS)<br>* Transauricular vagus nerve stimulation (taVNS) is a simple technique in which small surface electrodes are placed over the skin of the ear that are thought to be innervated by the auricular branch of the vagus nerve (ABVN).<br>|
| Sham Comparator: Sham taVNS<br>Sham condition will have the same device, with an earset, and conductive eartips placed in the same location of the active stimulation; however during 60 min there will be no current and the device will be turned off. | Device: Transauricular vagus nerve stimulation (taVNS)<br>* Transauricular vagus nerve stimulation (taVNS) is a simple technique in which small surface electrodes are placed over the skin of the ear that are thought to be innervated by the auricular branch of the vagus nerve (ABVN).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Resting-state electroencephalogram (EEG) | Electroencephalogram (EEG) will be recorded using the 64-channel EGI system (Electrical Geodesics, Inc)(EGI, Eugene, USA) using a high-density electrode array from two resting state conditions: eyes open and eyes closed. Fourier transformation (STFT) will be applied to filter the data into five typically analyzed frequency bands, delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (13-30 Hz) and gamma (30-80 Hz) bands. | Change from baseline resting-state EEG at 60 minutes. | 
| Electroencephalogram (EEG) event-related potentials | Electroencephalogram (EEG) will be recorded using the 64-channel EGI system (Electrical Geodesics, Inc)(EGI, Eugene, USA) using a high-density electrode array continuously during visual task stimulus presentation and go/no-go task. Event-related potential amplitudes and latencies will be measured from frontal, central, parietal, and occipital areas. We will analyze five frequency bands, delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (13-30 Hz) and gamma (30-80 Hz) bands. | Change from baseline EEG event-related potentials at 60 minutes. | 
| Quantitative sensory testing (QST) | We will find the pain-60 temperature by applying a thermode on the right forearm and delivering short heats that we increased, 1°C each wave, gradually from 41 to 48°C until patients rated their level of pain as 60, generated by a TSA-II Stimulator (Medoc Ltd). Once determined, we will administer the test stimulus for 30s at that temperature and ask them to rate their levels of pain at 10, 20, and 30s. For the conditioned stimulus, the left hand of the subject will be immersed in water at 10 to 12°C for 30s. Then, the same temperature will be applied to the right forearm - with the left hand still immersed - at 10, 20, and 30s. CPM response will be calculated as the difference between the average pain ratings from the test stimulus minus the conditioned stimulus. | Change from baseline QST at 60 minutes. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Heart rate variability (HRV) | HRV will be collected from the non-dominant hand following a standardized protocol. The measurements will be taken at baseline, during, and after stimulation. | Change from baseline HRV at 60 minutes. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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vagal nerve stimulation, healthy subjects, biomarkers