The author is grateful to the research team (Maria Fernanda Andrade, Allison Kim, Robin Heemels).

All study procedures were performed at the Spaulding Neuromodulation Center/Spaulding Cambridge Hospital. Ethical approval for this protocol was obtained from Mass General Brigham IRB (Number Protocol #:2022P003200). Informed consent was obtained from all subjects using the encrypted Research Electronic Data Capture (REDCap) platform (see Table of Materials). Trial registration number: NCT05801809.
1. Subject selection and screening
<ol>
	<li>Identify potent...

Measurement of Neuromodulation by Transcutaneous Auricular Vagus Nerve  Stimulation

<ol>
	<li>Ben-Menachem, E., Revesz, D., Simon, B. J., Silberstein, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surgically+implanted+and+non-invasive+vagus+nerve+stimulation:+a+review+of+efficacy,+safety+and+tolerability.">Surgically implanted and non-invasive vagus nerve stimulation: a review of efficacy, safety and tolerability.</a> Eur J Neurol. 22 (9), 1260-1268 (2015).</li><li>Johnson, R. L., Wilson, C. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+vagus+nerve+stimulation+as+a+therapeutic+intervention.">A review of vagus nerve stimulation as a therapeutic intervention.</a> J Inflamm Res. 11, 203-213 (2018).</li><li>Gianlorenco, A. C. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroencephalographic+patterns+in+taVNS:+A+systematic+review.">Electroencephalographic patterns in taVNS: A systematic review.</a> Biomedicines. 10 (9), 2208 (2022).</li><li>Ruhnau, P., Zaehle, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcranial+Auricular+Vagus+Nerve+Stimulation+(taVNS)+and+Ear-EEG:+Potential+for+closed-loop+portable+non-invasive+brain+stimulation.">Transcranial Auricular Vagus Nerve Stimulation (taVNS) and Ear-EEG: Potential for closed-loop portable non-invasive brain stimulation.</a> Front Hum Neurosci. 15, 699473 (2021).</li><li>Coan, J. A., Allen, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Frontal+EEG+asymmetry+as+a+moderator+and+mediator+of+emotion.">Frontal EEG asymmetry as a moderator and mediator of emotion.</a> Biol Psychol. 67 (1-2), 7-49 (2004).</li><li>Davidson, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebral+asymmetry,+emotion,+and+affective+style.">Cerebral asymmetry, emotion, and affective style.</a> Brain Asymmetry. , 361-387 (1995).</li><li>de Aguiar Neto, F. S., Rosa, J. L. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Depression+biomarkers+using+non-invasive+EEG:+A+review.">Depression biomarkers using non-invasive EEG: A review.</a> Neurosci Biobehav Rev. 105, 83-93 (2019).</li><li>Rao, R. P. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Brain-Computer Interfacing: An Introduction. , (2013).</li><li>Machetanz, K., Berelidze, L., Guggenberger, R., Gharabaghi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=brain-heart+interaction+during+Transcutaneous+Auricular+Vagus+Nerve+Stimulation.">brain-heart interaction during Transcutaneous Auricular Vagus Nerve Stimulation.</a> Front Neurosci. 15, 632697 (2021).</li><li>Spyer, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Annual+review+prize+lecture.+Central+nervous+mechanisms+contributing+to+cardiovascular+control.">Annual review prize lecture. Central nervous mechanisms contributing to cardiovascular control.</a> J Physiol. 474 (1), 1-19 (1994).</li><li>Jarczok, M. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigating+the+associations+of+self-rated+health:+heart+rate+variability+is+more+strongly+associated+than+inflammatory+and+other+frequently+used+biomarkers+in+a+cross+sectional+occupational+sample.">Investigating the associations of self-rated health: heart rate variability is more strongly associated than inflammatory and other frequently used biomarkers in a cross sectional occupational sample.</a> PLoS One. 10 (2), 0117196 (2015).</li><li>Shaffer, F., Ginsberg, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+overview+of+heart+rate+variability+metrics+and+norms.">An overview of heart rate variability metrics and norms.</a> Front Public Health. 5, 258 (2017).</li><li>Haensel, A., Mills, P. J., Nelesen, R. A., Ziegler, M. G., Dimsdale, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationship+between+heart+rate+variability+and+inflammatory+markers+in+cardiovascular+diseases.">The relationship between heart rate variability and inflammatory markers in cardiovascular diseases.</a> PNEC. 33 (10), 1305-1312 (2008).</li><li>Wolf, V., K&#252;hnel, A., Teckentrup, V., Koenig, J., Kroemer, N. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Does+transcutaneous+auricular+vagus+nerve+stimulation+affect+vagally+mediated+heart+rate+variability?+A+living+and+interactive+Bayesian+meta-analysis.">Does transcutaneous auricular vagus nerve stimulation affect vagally mediated heart rate variability? A living and interactive Bayesian meta-analysis.</a> Psychophysiol. 58 (11), e13933 (2021).</li><li>Geng, D., Liu, X., Wang, Y., Wang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+transcutaneous+auricular+vagus+nerve+stimulation+on+HRV+in+healthy+young+people.">The effect of transcutaneous auricular vagus nerve stimulation on HRV in healthy young people.</a> PLoS One. 17 (2), 0263833 (2022).</li><li>Garrido, M. V., Prada, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=KDEF-PT:+Valence,+emotional+intensity,+familiarity+and+attractiveness+ratings+of+angry,+neutral,+and+happy+faces.">KDEF-PT: Valence, emotional intensity, familiarity and attractiveness ratings of angry, neutral, and happy faces.</a> Front Psychol. 8, 2181 (2017).</li><li>Granot, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determinants+of+endogenous+analgesia+magnitude+in+a+diffuse+noxious+inhibitory+control+(DNIC)+paradigm:+do+conditioning+stimulus+painfulness,+gender+and+personality+variables+matter.">Determinants of endogenous analgesia magnitude in a diffuse noxious inhibitory control (DNIC) paradigm: do conditioning stimulus painfulness, gender and personality variables matter.</a> Pain. 136 (1-2), 142-149 (2008).</li><li>Nirl, R. 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F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+prevalence+and+burden+of+depressive+and+anxiety+disorders+in+204+countries+and+territories+in+2020+due+to+the+COVID-19+pandemic.">Global prevalence and burden of depressive and anxiety disorders in 204 countries and territories in 2020 due to the COVID-19 pandemic.</a> Lancet. 398 (10312), 1700-1712 (2021).</li><li>Tan, C., Yan, Q., Ma, Y., Fang, J., Yang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recognizing+the+role+of+the+vagus+nerve+in+depression+from+microbiota-gut+brain+axis.">Recognizing the role of the vagus nerve in depression from microbiota-gut brain axis.</a> Front. Neurol. 13, 1015175 (2022).</li><li>Kim, A. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safety+of+transcutaneous+auricular+vagus+nerve+stimulation+(taVNS):+A+systematic+review+and+meta-analysis.">Safety of transcutaneous auricular vagus nerve stimulation (taVNS): A systematic review and meta-analysis.</a> Sci. Rep. 12 (1), 22055 (2022).</li><li>Martins, D. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+the+vagus+nerve+in+fibromyalgia+syndrome.">The role of the vagus nerve in fibromyalgia syndrome.</a> Neurosci. Biobehav. Rev. 131, 1136-1149 (2021).</li><li>Fr&#248;kjaer, J. 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Transauricular Vagus Nerve Stimulation (taVNS) is emerging as a promising therapeutic avenue for addressing several neuropsychiatric conditions. Mood disorders, such as depression and anxiety, pose a significant global health burden, especially after the COVID-19 pandemic19. Recent studies exploring taVNS have exhibited the potential to alleviate symptoms associated with these disorders. 
The vagus nerve plays a pivotal role in the brain-gut axis and the regulation of e...

Transauricular vagus nerve stimulation (taVNS) is a recent neuromodulation technique that does not require surgery and utilizes a non-invasive stimulation device placed at the concha or tragus of the ear. Consequently, it is more accessible and safer for patients1. In recent years, the taVNS field has rapidly expanded, primarily focusing on clinical trials demonstrating potential therapeutic advantages for various pathological conditions, including epilepsy, depression, tinnitus, Parkinson's disease, impaired glucose tolerance, schizophrenia, and atrial fibrillation2. There is much to discuss about taVNS and its effects on biological processes in the central and peripheral systems. Ideally, a biological marker might demonstrate that the auricular branch of the vagus was stimulated, affecting intracranial structures and allowing researchers to analyze how taVNS affects physiological function. Nevertheless, without a trustworthy biomarker, it is not easy to understand what the taVNS data mean and how to interpret them effectively.
Electroencephalography (EEG) is an encouraging imaging tool to provide biomarkers for taVNS. It is a non-invasive, reliable, inexpensive approach to measure and quantify cortical activity3,4. Following this process, our group performed a systematic review, demonstrating elementary details that taVNS could influence cortical activity, mainly increasing EEG power spectrum activity in lower frequencies (delta and theta). However, diverse results in higher frequencies (alpha) and changes in early ERP components related to inhibitory tasks were also detected. High heterogeneity between the studies was found; therefore, more homogeneous, more significant, and well-planned studies are essential to make more robust conclusions about the effects of taVNS on brain activity measured by EEG3. Assessing EEG during taVNS could advance future research on integrating the two techniques for a mobile, closed-loop, monitoring, and non-invasive stimulation tool to affect brain oscillatory activity4.
Alpha asymmetry, which assesses the relative alpha band activity between the brain hemispheres, particularly at frontal electrodes, is a frequently researched EEG biomarker. Previous literature has used this biomarker to analyze the approach-withdraw hypothesis5,6, which holds that the right frontal side of the brain is associated with withdrawal behaviors. In contrast, the left frontal side is associated with approach behaviors. Since alpha is associated with low brain activity, an increase in alpha on the left side of the brain suggests lower activity and may show a lack of approach behavior. This concept helps to explain some results in the alpha band at the left side hemisphere in depressed patients7. Additionally, EEG electrodes record the activity of neuronal populations, examining Functional Connectivity (FC) or changes in large-scale brain networks, such as the default mode network (DMN)7,8.
Based on that, quantitative electroencephalography can be employed to assess the effects of taVNS on brain activity; however, more studies are required to systematically demonstrate the specific metrics and effects that would highlight the non-invasive stimulation through the auricular branch of the vagus nerve.
Peripherally, the vagus nerve and sympathetic nervous system mediate the heart's contractile and electrical function9. This regulation promotes the heart's pacemaker ability and controls it through physiological manifestations of the body, known as sinus depolarizations. Heart rate variability (HRV) records the changes per beat of sinus depolarization, thus non-invasively describing vagal influences on the sinus node10. Given this function, HRV has been seen and studied as a prominent neurocardiac function biomarker associated with an individual's well-being and the likelihood of morbidity, mortality, and stress11,12.
In the context of taVNS, HRV has been recorded in many trials, and stimulation has been thought to modulate HRV9,11,12. Considering that decreased HRV has been related to the morbidity and mortality of different diseases through mechanisms such as over-activity of the sympathetic nervous system, inflammatory response, and oxidative stress, the vagal nerve modulation of taVNS is thought to directly impact HRV and its sinus regulation13,14. In fact, some trials have already indicated that taVNS can increase HRV in healthy subjects, thus supporting this hypothesis15,16. However, there is still a need to understand better whether different taVNS parameters can affect HRV differently.
Currently, no mechanistic studies have investigated the taVNS neural network and autonomic nervous system effects of this technique together. Therefore, this protocol aims to assess how taVNS can affect EEG metrics and HRV and evaluate its safety. Additionally, this also aims to identify predictors that can influence the response to taVNS. Understanding the variables associated with the response to taVNS can help design future clinical trials to maximize the effects of this intervention.

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	<tbody>
		<tr>
			<td>Articulated arm</td>
			<td>Electrical Geodesics, Inc.</td>
			<td>20090645</td>
			<td></td>
		</tr>
		<tr>
			<td>Baby shampoo</td>
			<td>Dynarex</td>
			<td>1396</td>
			<td></td>
		</tr>
		<tr>
			<td>Charge Cable</td>
			<td>NEURIVE Co.</td>
			<td>HV12303003</td>
			<td></td>
		</tr>
		<tr>
			<td>Computer</td>
			<td>Apple</td>
			<td>YM92704U4PC</td>
			<td></td>
		</tr>
		<tr>
			<td>Condutive eartip</td>
			<td>NEURIVE Co.</td>
			<td>HV12303003</td>
			<td></td>
		</tr>
		<tr>
			<td>Earset</td>
			<td>NEURIVE Co.</td>
			<td>HV12303003</td>
			<td></td>
		</tr>
		<tr>
			<td>EEG 64-channel cap&#160;</td>
			<td>Electrical Geodesics, Inc.</td>
			<td>H11333</td>
			<td></td>
		</tr>
		<tr>
			<td>Heart rate sensor</td>
			<td>Polar</td>
			<td>M311370175396</td>
			<td></td>
		</tr>
		<tr>
			<td>Monitor</td>
			<td>Dell</td>
			<td>REVA01</td>
			<td></td>
		</tr>
		<tr>
			<td>Net Amps 300</td>
			<td>Electrical Geodesics, Inc.</td>
			<td>A09370244</td>
			<td></td>
		</tr>
		<tr>
			<td>Peltier thermode</td>
			<td>Advanced Medical Systems, Ramat Yishai, Isreal</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Chloride (dry)</td>
			<td>Electrical Geodesics, Inc.</td>
			<td>820127755</td>
			<td></td>
		</tr>
		<tr>
			<td>Rally</td>
			<td>Mass General Brigham Research</td>
			<td></td>
			<td>online platform</td>
		</tr>
		<tr>
			<td>Research Electronic Data Capture (REDCap)</td>
			<td>Vanderbilt</td>
			<td></td>
			<td>web-based software platform</td>
		</tr>
		<tr>
			<td>Thermosensory Stimulator</td>
			<td>Medoc Ltd</td>
			<td>1241</td>
			<td></td>
		</tr>
		<tr>
			<td>Transauricular vagus nerve stimulator</td>
			<td>NEURIVE Co.</td>
			<td>HV12303003</td>
			<td></td>
		</tr>
	</tbody>
</table>

understanding the effects of non&#45;invasive transauricular vagus nerve stimulation on eeg and hrv

Several studies have demonstrated promising results of transcutaneous auricular vagus nerve stimulation (taVNS) in treating various disorders; however, no mechanistic studies have investigated this technique's neural network and autonomic nervous system effects. This study aims to describe how taVNS can affect EEG metrics, HRV, and pain levels. Healthy subjects were randomly allocated into two groups: the active taVNS group and the sham taVNS group. Electroencephalography (EEG) and Heart Rate Variability (HRV) were recorded at baseline, 30 min, and after 60 min of 30 Hz, 200-250 &#181;s taVNS, or sham stimulation, and the differences between the metrics were calculated. Regarding vagal projections, some studies have demonstrated the role of the vagus nerve in modulating brain activity, the autonomic system, and pain pathways. However, more data is still needed to understand the mechanisms of taVNS on these systems. In this context, this study presents methods to provide data for a deeper discussion about the physiological impacts of this technique, which can help future therapeutic investigations in various conditions.

Author Spotlight: Exploring the Effects of Transauricular Vagus Nerve Stimulation

Understanding the Effects of Non&#45;Invasive Transauricular Vagus Nerve Stimulation on EEG and HRV

Transauricular Vagus Nerve Stimulation, taVNS for short, is a safe, noninvasive 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 afferent 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 taVNS on psychological processes, therefore establishing a baseline understanding of how taVNS influences neurophysiological mechanisms, fostering confidence in the techniques 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.

We performed a preliminary descriptive analysis of the first randomized subject without unblinding the study. For this reason, which arms this subject was allocated to is unknown. The first subject is a 69-year-old woman, non-Hispanic, Caucasian, with a college degree, who did not report any adverse event during or after the stimulation session. The clinical data are displayed in Table 2.
Besides, a topographic distribution of scalp plots was created in resting-state EEG for t...

Read this Scientific Article Protocol about Author Spotlight: Exploring the Effects of Transauricular Vagus Nerve Stimulation at JoVE.com

This protocol provides information on how to apply transcutaneous auricular vagus nerve stimulation (taVNS) in a clinical trial, including potential biomarkers such as EEG metrics and heart rate variability (HRV) to measure the effect of this treatment on the autonomic nervous system.

Several studies have demonstrated promising results of transcutaneous auricular vagus nerve stimulation (taVNS) in treating various disorders; however, no ...