Transauricular Vagus Nerve Stimulation, taVNS for short, is a safe non-invasive stimulation technique that targets the auricular branch of the vagus nerve. Placing the electrodes at the concha of the ear, as an alternative to invasive stimulation, taVNS can affect several brain functions by stimulating the vagal afrins fibers. Several studies have demonstrated promising results of taVNS.
However, there is a lack of mechanistic studies to investigate its effect on neural network and autonomic nervous system. So in this clinical trial, we are assessing taVNS in health subjects, looking for potential biomarkers such as EEG metrics and heart rate variability. With this protocol, we are proposing a bilateral stimulation that does not significantly increase the likelihood of cardiovascular events, but enhances the effect of vagus stimulation.
taVNS holds significant promise for addressing mood disorders and chronic pain conditions among others. This study will provide insights into the safety, feasibility and general effects of the taVNS on psychological processes. Therefore, establishing a baseline understanding of how taVNS influences neuro-physiological mechanisms, fostering confidence in the technique's potential therapeutic value.
Understanding the variables associated with response to taVNS can help design future clinical trials to maximize the effects of this intervention. Based on that, our studies will be focused on how taVNS can be optimized to target specific neural pathways and treat different conditions. To begin, open an envelope containing the concealed randomization and prepare the correct active or sham device.
Hand the device over to the blinded investigator. Use the electronic format capture system or REDCap, to collect the data for this study with the subject. To start the QST Assessment, apply a Peltier Thermode to the right forearm of the subject to deliver short heat stimuli.
Instruct the subject to rate the pain intensity from zero to 100. Next, apply the test stimulus for 30 seconds at the test temperature. Ask the subject to rate the pain intensity at 10 second intervals from 10 to 30 seconds, after the thermode reaches the pain 60 temperature.
Five minutes after delivering the test stimulus, immerse the left hand of the subject in a water bath set between 10 to 12 degrees Celsius for 30 seconds. Then apply the same pain 60 temperature on the subject's right forearm, before asking him to rate the pain intensity. Now, ask the subjects to place a Heart Rate Variability or HRV monitor on their person.
Submerge the EEG cap in one liter of water with 11 grams of potassium chloride and five milliliters of baby shampoo for 10 to 15 minutes. Next, position the subject comfortably on the chair. Then cover the subject's shoulders with large towels.
To locate the vertex, place a mark at the halfway distance between nasion and inion. Mark the halfway distance between both preauricular points. Then mark the intersection of both marks.
Place the EEG cap carefully on the subject's head. Connect the EEG to a computer system and start the resting assessments. Simultaneously, assess the baseline HRV for five minutes on a tablet connected to the monitor via Bluetooth, before assessing the EEG.
Next, to perform the task related to the EEG assessment, clean the skin of the subject's ear with a 70%alcohol pad. Apply saline to the ear tips, then place the electrodes on the ear and check the current quality. Start the stimulation using the TAVNS.
After 60 minutes of stimulation, measure the subject for EEG, HRV, and pain. Then perform conditioned pain modulation as before. A topographic distribution of scalp plots was created in resting state EEG for Theta, Alpha, and Beta bands, in the Baseline, During and Post procedure.
An Asymmetric Alpha Pattern was noticed in the frontal region.
