Vagus nerve stimulation: can we influence our brain and our health through the ear?

What is the vagus nerve?

The vagus nerve is the tenth cranial nerve (cranial nerve X) and one of the main communication channels between the brain and numerous organs. Its name comes from the Latin vagus, meaning 'wandering,' precisely because it travels through a large part of the body.

From the brainstem it descends toward the neck, thorax, and abdomen, and is involved in communication with structures such as the heart, lungs, digestive system, liver, pancreas, and various visceral structures. It is also one of the fundamental components of the parasympathetic nervous system.

To put it simply, our body permanently maintains a balance between two major systems: the sympathetic system (activation, alertness, stress response) and the parasympathetic system (recovery, regulation, digestion, and energy conservation). The vagus nerve constitutes one of the main pathways of the second system.

The vagus nerve does not only send signals from the brain to the body

We often picture nerves as cables through which the brain sends instructions to our organs. In the case of the vagus nerve, the opposite also occurs: a large proportion of its fibers are afferent, meaning they transmit information from the body to the brain.

The vagus nerve therefore functions as a true bidirectional highway between the brain, the nerve itself, and the body. This characteristic explains why its stimulation can potentially modify certain brain circuits.

What does the ear have to do with the vagus nerve?

This is where the most surprising part begins. A small branch of the vagus nerve, known as the auricular branch of the vagus nerve (ABVN), provides sensory innervation to certain areas of the external ear. Among the regions used in research are especially the tragus, the auricular concha, and in particular the cymba conchae.

This means it is possible to apply small electrical impulses to specific areas of the ear and indirectly stimulate fibers related to the vagal system, without the need to surgically implant any electrodes. This is the origin of taVNS: transcutaneous auricular vagus nerve stimulation.

What happens when we stimulate these fibers?

The signals generated by auricular stimulation can reach brainstem structures involved in autonomic and neurological regulation. One of the main pathways studied is the following: ear → auricular branch of the vagus nerve → nucleus of the solitary tract (NTS) → locus coeruleus → noradrenaline → brain networks related to attention, pain, alertness, emotions, and executive functions.

The nucleus of the solitary tract constitutes one of the main brain centers that receive vagal information. From there, connections exist with numerous brain regions, including the locus coeruleus, the raphe nuclei, the hypothalamus, the amygdala, the insula, the thalamus, and cortical regions. Neuroimaging studies have observed changes in activity and connectivity in some of these networks during auricular vagal stimulation.

This does not mean that we can 'control the brain from the ear.' It means something scientifically far more interesting: we can modulate certain neurophysiological pathways through non-invasive peripheral stimulation.

The locus coeruleus: a particularly interesting piece

The locus coeruleus is a small structure located in the brainstem. Despite its size, it constitutes one of the main sources of cerebral noradrenaline. It is involved in functions such as attention, concentration, vigilance, learning, memory, stress adaptation, emotional regulation, and pain perception.

The functional connection vagus nerve → NTS → locus coeruleus → noradrenaline is precisely one of the reasons why vagal stimulation is generating so much interest in neuroscience.

What is taVNS being researched for?

Here we must clearly distinguish between applications with growing clinical evidence and those that are still experimental. Studies currently exist across numerous fields.

1. Migraine

Migraine is probably one of the most interesting neurological applications of vagal neuromodulation. Migraine is not simply 'a headache': it is a complex neurological disease involving different mechanisms related to the trigeminovascular system, neuronal excitability, central pain processing, neurotransmitters, peptides such as CGRP, and brain pain-modulation networks. Vagal stimulation may interact with some of these circuits.

Clinical research on non-invasive vagus nerve stimulation (nVNS) in migraine is already considerable. A meta-analysis of randomized clinical trials published in 2026 brought together 7 studies and 917 patients with migraine. Overall, nVNS was associated with reductions in monthly headache days, monthly acute medication use, and pain intensity.

It is important to introduce a clarification: these studies include both cervical vagal stimulation and auricular stimulation, and the devices and protocols are not all equivalent. Therefore, vagal neuromodulation constitutes a promising strategy for certain people with migraine, but not all vagal stimulation devices can automatically be considered equivalent.

2. Sleep and insomnia

Another particularly interesting field is sleep. Sleep depends on an extremely complex balance between brain activation systems and systems that facilitate rest, and autonomic regulation also plays an important role.

In 2024, a randomized clinical trial on taVNS in patients with chronic insomnia was published. 72 participants were assigned to active or sham stimulation. After eight weeks, the group treated with taVNS showed significantly greater improvement in sleep quality as measured by the Pittsburgh Sleep Quality Index (PSQI). Another double-blind trial published in 2025, using 30 minutes daily for six weeks, also found improvements in sleep quality and insomnia severity compared with sham stimulation.

These are interesting results. But this does not mean that a person who sleeps well will necessarily sleep even better by using vagal stimulation: results obtained in patients with insomnia should not be automatically extrapolated to healthy individuals.

3. Attention, concentration and ADHD

This is probably one of the most fascinating fields from a neurobiological standpoint. ADHD — Attention Deficit Hyperactivity Disorder — involves complex alterations in different brain networks. Among the systems implicated are the dopaminergic and noradrenergic pathways.

Noradrenaline in particular plays a fundamental role in the functioning of the prefrontal cortex, which is linked to sustained attention, working memory, planning, impulse inhibition and executive control. As we have seen: taVNS → NTS → locus coeruleus → noradrenaline. For this reason, researchers are investigating whether auricular vagal stimulation could modulate certain processes related to attention.

A review published in Frontiers in Neuroscience examined this hypothesis specifically in ADHD. The neurophysiological basis is plausible. Nevertheless, we must be rigorous: taVNS does not yet constitute an established treatment for ADHD, and specific clinical research in this indication remains limited. At present, therefore, we should speak of a promising avenue of research, not a proven alternative to conventional treatments.

4. Stress and autonomic nervous system regulation

We live under constant exposure to stimuli that activate our nervous system: work, problems, relentless information, screens, lack of rest, responsibilities. Our body needs to alternate adequately between activation and recovery, and the vagal system plays a key role in this autonomic regulation. This is why researchers are investigating whether taVNS can modify certain aspects of the physiological stress response.

However, we must avoid a very common oversimplification on social media: 'stimulating the vagus nerve automatically increases vagal tone.' The physiology is more complex. For example, although heart rate variability (HRV) is frequently used as an indirect marker of autonomic regulation, a meta-analysis of studies conducted in healthy subjects found no convincing evidence that a single acute session of taVNS consistently increased HRV compared with sham stimulation.

This is an excellent example of why we must distinguish between a plausible physiological mechanism and a clinically demonstrated biomarker.

5. Inflammation: the inflammatory reflex

This is another of the most fascinating areas of research on the vagus nerve. Our nervous system and our immune system do not function independently: there is constant communication between the two. A mechanism known as the 'inflammatory reflex' has been described, in which certain vagal pathways may participate in the regulation of inflammatory responses. One of the pathways studied is known as the cholinergic anti-inflammatory pathway.

Experimentally, vagal signaling can influence the production of certain inflammatory cytokines. This has led to research into vagal stimulation in various diseases characterized by inflammation. Small clinical trials have found modifications in inflammatory biomarkers in certain contexts, including hospitalized patients with sepsis, COVID-19, or stroke.

But once again we must avoid drawing conclusions too hastily. We cannot claim that using a vagal stimulator on a daily basis 'eliminates chronic inflammation': current evidence does not support such a claim. What we can say is that the communication between the nervous system and immunity through vagal pathways represents an extremely interesting field of research.

6. Pain

Pain is not simply a signal coming from injured tissue: it is a complex neurological experience processed by numerous brain structures. Vagal stimulation can interact with regions involved in pain modulation, including circuits related to the brainstem, the thalamus, the insula, the cingulate cortex, and the periaqueductal gray matter.

For this reason, vagal neuromodulation is being studied in various pain syndromes. In migraine, for example, functional MRI studies have observed changes in connectivity between the periaqueductal gray matter and other brain regions during taVNS. We still need a better understanding of which patients may benefit, with which parameters, and for how long.

Can it be used in healthy people?

This is a different question. A person might think: 'I have no illness. Does it make sense to stimulate my vagus nerve to improve my health?' At present, we must answer with caution.

There are experimental studies in healthy subjects investigating attention, learning, memory, autonomic regulation, stress response, and cognitive performance. However, there is not yet sufficient evidence to claim that daily vagal stimulation in a healthy person prolongs life, prevents disease, systematically increases energy, permanently improves concentration, or produces a general 'longevity' effect.

These are interesting hypotheses; they are not established facts. Preventive medicine does not consist of using every available technology, but of distinguishing which ones have sufficient evidence for each specific goal.

How long does the stimulation session last?

Here too, there is no universal protocol. Scientific studies use very different parameters: different frequencies, different intensities, different auricular zones, sessions of varying durations, one or several sessions per day, and treatments ranging from a few days to several weeks or months.

Some recent trials in insomnia have used 30-minute sessions; other experimental protocols use completely different durations. Therefore, '30 minutes' should not be interpreted as a universal medical dose: parameters must depend on the device used, its design, the indication being studied, and the corresponding protocol.

Does greater intensity mean greater effect?

No. This is a fundamental concept in neuromodulation: greater intensity does not necessarily mean greater benefit. The stimulation must be sufficient to activate the target fibers without causing pain or unnecessarily intense stimulation.

In many experimental protocols, intensity is adjusted until a perceptible but comfortable sensation is produced. Neuromodulation does not work like muscle training, where we necessarily need to progressively increase the load.

Is taVNS safe?

In general terms, the available studies show a favorable safety profile. A systematic review and meta-analysis published in Scientific Reports analyzed 177 studies including 6,322 participants. The most frequently reported adverse effects were discomfort or pain in the ear, tingling, headache, and local irritation. No causal relationship between taVNS and serious adverse events was found in that review.

However, there is an important limitation: the reporting of adverse effects was not sufficiently systematic across numerous studies. Therefore, 'well tolerated' does not mean 'without any precautions.'

Who should exercise special caution?

Vagal stimulation should not be considered simply an electronic wellness device. Before using a specific device, its contraindications, medical instructions, and technical characteristics should always be reviewed.

Special caution may be necessary, depending on the device and the clinical situation, in people with certain implanted electronic devices, significant cardiac rhythm disorders, significant bradycardia, unexplained recurrent syncope, certain cardiovascular conditions, pregnancy (when the device has not been sufficiently studied), or significant skin lesions and diseases in the area where the electrode is placed. And, of course, a person with new or unexplained neurological symptoms should not use neuromodulation to delay a medical diagnosis.

Neuromodulation does not mean 'curing everything'

Every new medical technology goes through practically the same cycle. First comes the discovery; then comes the enthusiasm; and finally comes the science, which determines what works, for whom it works, how well it works, and under what conditions.

Transcutaneous vagus nerve stimulation is at a particularly exciting stage in this process. We have plausible neurobiological mechanisms, neuroimaging studies, randomized clinical trials, promising results in certain conditions, and a growing body of research. But major questions still remain.

What we still do not know

We need a better understanding of what the optimal frequency is, what the optimal intensity is, what the ideal duration of each session is, and which area of the ear is most effective for each goal. We also need to know whether there is a different response depending on the individual, which biomarkers can identify responders, whether the benefits are maintained in the long term, which conditions genuinely respond, and which devices produce physiologically equivalent vagal stimulation.

These questions are fundamental, because the future of neuromodulation will probably not simply be a matter of 'stimulating the vagus nerve,' but rather stimulating it with specific parameters, in specific patients, and for specific goals.

The future: a medicine that does not rely solely on drugs

For decades we have modified physiology primarily through molecules: a medication enters the body and alters a particular biological pathway. Neuromodulation proposes a different strategy: instead of introducing a molecule, we modify a signal — electricity, frequency, impulses, nerve circuits.

Our body functions through chemistry, but also through electrical signals. That is why the medicine of the future will likely combine pharmacology, biology, physical stimulation, and neuromodulation to an ever-greater degree.

In summary

Transcutaneous auricular vagus nerve stimulation, or taVNS, makes it possible to stimulate specific nerve fibers from particular areas of the ear using small electrical impulses. These signals can reach brainstem circuits connected to structures such as the nucleus tractus solitarius and the locus coeruleus, and from there influence networks involved in attention, pain, autonomic regulation, and other processes.

There is currently particularly interesting research underway in migraine, insomnia, pain, autonomic regulation, attention and cognitive function, ADHD, inflammation, and certain neurological and psychiatric conditions. However, the level of evidence is not the same across all these applications: some already have controlled clinical trials, while others remain primarily experimental.

The most important idea

The vagus nerve is far more than a nerve that controls digestion or slows the heart rate: it is a vast communication pathway between our brain and our body. And today we are beginning to discover that we can interact with part of that system without surgery, from a small region of the ear. This opens a new door in medicine — but a new door does not mean a solution for every disease.

I am Dr. Florian Vallecillo, and good medicine consists precisely in maintaining two things simultaneously: curiosity about new technologies and rigour in not promising more than science has demonstrated. Non-invasive vagal stimulation is a technology that deserves to be followed very closely, because we may be witnessing only the beginning of a new generation of treatments based not solely on medications, but also on the precise modulation of our own neural circuits.