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Vagus.net tVNS Stimulators

Scientists published last month in Elsevier Journal of Public Health findings that further linked symptoms of vagal nerve neuropathy to damage resulting directly from covid infection. 

Some symptoms such as difficulty swallowing had been previously thought to be more likely triggered by a period of intubation. But this study found that such symptoms also typically occur even in patients who never go intubation. 

SARS-CoV-2 is known to cause neurological effects in 36% of infected individuals. This can lead to a number of symptoms, from mild headaches to more severe cases of (though rare) meningitis, epilepsy or stroke. 

Commenting on the findings, Prof Kevin Tracy MD, Feinstein Institutes for Medical Research, said that this new study combined with other evidence indicated that it was vagal nerve damage from covid that was interfering with the body’s normal inflammatory reflex, “which normally inhibits inflammation [and so] contributes to the onset of the cytokine storm in Covid19.” 

Prof Kevin Tracy has in previous publications highlighted the anti-inflammatory potential of vagus nerve stimulation.

This is a question that we are increasingly asked by existing and potential customers. In most cases, the answer to this question is unfortunately: no, you should not use a TENS machine for vagus nerve stimulation. It’s possible to use one, but we strongly recommend against it. At best, most TENS machines will be inconsistent, ineffective or both. At worst, they could be harmful rather than helpful; and under some conditions, they may even be dangerous.

To understand why we recommend against the use of TENS, we need to understand the difference between voltage-controlled and current-controlled devices.

 

Voltage Control vs Current Control

TENs machines are typically voltage-controlled (VC) devices: meaning they work by applying predefined voltages across electrodes. However, it isn’t voltage that stimulates the nerve, but rather the current that results from the applied voltage. And the current that flows from a given voltage is also a function of the resistance, following Ohm’s Law:

Current (I) = Voltage (V) / Resistance (R)

This means that in conditions of high resistance a predefined voltage will drive too little current and therefore result in too little stimulation. Worse still, in conditions of low resistance, too much current will lead to over-stimulation of the nerve which could result in more harm than good.

The level of resistance in biological systems is highly unpredictable. The resistance experienced at the electrode-skin interface varies greatly, even within a single stimulation session. So there is never a case when a predefined voltage will provide a constant and reliable level of stimulation throughout a single session.

When researchers (and medics) first began experimenting with vagus nerve stimulation it was common to use voltage-controlled stimulation devices. This was mainly because they were cheaper and more widely available due to the fact that the circuitry and electronics for VC devices is much simpler than for current-controlled devices.

However, VC devices produce unpredictable results, making reproducibility of experimental results difficult. So there has been a growing consensus that to stimulate nerves it is best to use a current-controlled device.

A current-controlled device will repeatedly sample the current and dynamically adjust the voltage to maintain the current at the desired level. The vagunet device actually samples the current thousands of times per second to ensure that the right amount of current is always being delivered throughout the stimulation session.

With current controlled devices, you can always be sure how much current (and therefore stimulation) the nerve receives.

Your brain is actually the centre of a vast network of nerves - a complex system that extends throughout your body. Scientists refer to the brain and the spinal cord as the central nervous system and everything else as the peripheral nervous system.

The peripheral nervous system is a bi-directional information highway, sending information from bodily organs to the brain and operational instructions from the brain back to the body.

Some nerves carry information from our sensory organs -- such as our eyes, ears and skin. These help the brain to build a detailed perceptual picture of the world around us. Scientists call this exteroception.

But we also have an often overlooked set of nerves which deal with interoception -- the sensing of the internal state of the body. Some of this perception of bodily state (such as pain) is just as clear and sharp as the sensations of the outside word. But we also receive interoceptive nerve signals from our visceral (internal) organs which tends to be less sharp but in no way less important. Probably the most important interoceptive nerve in our body is the vagus nerve which connects all of these visceral organs to the brain.

The sensations we receive along the vagus nerve tell the brain about the state of these organs; and signals from the brain control the function of these organs - everything from the beating of your heart to the digestion of food in your stomach and intestines to the filtering of blood through your liver.

The vagus nerve forms a major part of half of the interoceptive nervous system called the parasympathetic nervous system. The other half is called the sympathetic nervous system. These two halves work together to maintain bodily homeostasis -- which refers to the body’s natural equilibrium state.

The sympathetic nervous system speeds up the body and becomes more active during stressful and dangerous situations; while the parasympathetic nervous system relaxes the body and becomes more active when we are in safe situations so that we can effectively regenerate and heal. Homeostasis is the balance between these two forces and is crucial for survival in the short term, and health and well being in the long term.

What we feel from our interoceptive nervous system is often vague compared to our exteroceptive perception. This is actually an important evolutionary adaptation. If our interoceptive perceptions were as loud and vivid as our exteroceptive perceptions, all we would ever hear would be the beating of our hearts, the air rushing into our lungs and the gurgles of our digestive system. These sounds would overwhelm external noises so much that we might not notice that sabre tooth tiger sneaking up on us.

But these sensations are nevertheless very important to survival. So the brain solves this problem by turning the sensations into broad emotions and vague feelings. This filtering can sometimes lead to confusion however -- for example when you get short tempered because you’re hungry.

And so, one of the consequences of this evolutionary adaptation is that when your vagus nerve is reporting a problem or has a problem with its own function, it’s not always easy to know. This uncertainty makes it a challenge to recognise when there might be a problem. Here are a few tips on what to look out for -- but remember, these are just guidelines. If you recognise any of the things below, it doesn’t necessarily mean that it’s caused by an issue with your vagus nerve, it just means you might benefit from trying out a few things.

Vagus nerve health (sometimes referred to as vagal tone) is worth improving even if you don’t experience any of the specific issues below. Like sticking to regular exercise and a healthy diet is good for you even if you don’t feel like anything in particular is wrong.

1. Mood and Memory

OK, mood changes can be caused by a lot of things, so just because you experience some, doesn’t mean you have issues with your vagus nerve. But emotions don’t occur in a void and like we said earlier, they are not only caused by external, environmental factors, but by the internal state of your body.

If you’re experiencing unusual and persistent mood swings, it could be a sign you have some underlying health issues.

The vagus nerve connects to all your visceral organs, so if the integrity of the vagus nerve declines, it hinders communication between the brain and these organs. This can be caused by and cause degrees of dysfunction in your organs. Early stages of this affects mood because, in a way, you feel that something is not quite right. So you may have inexplicable feelings of anxiety, sadness, tension, bouts of anger or general feelings of discomfort.

In some cases, it has been shown that dysfunction of the vagus nerve can also affect memory and cognition. Scientists still don’t fully understand the mechanisms, but studies have found solid links between good vagal tone and good mental health.

2. Energy and Blood Circulation

A lack of energy, feeling of weakness or fatigue, dizziness or fainting can all be signs that your heart and circulatory systems (the blood vessels) are not responding well to the oxygen and energy demands that are being placed on them. Our hearts actually respond from beat to beat to changes in the needs of the brain and body; and blood vessels expand and contract to regulate blood pressure. How well your heart adapts can be measured by your heart rate variability (HRV). You can learn more about this by reading our earlier post.

Experts are increasingly using HRV as a better measure of health and fitness than a simplistic average heart rate. A low HRV can be indicative of a number of underlying health issues.

As heart rate is highly regulated by the vagus nerve, it is one of the most useful indicators of vagal tone. Improving your HRV using diet and exercise or vagus nerve stimulation is one of the best things you can do for your long term health.

3. Digestive Issues

Your guts are like a second brain, containing more than 100 million neurons (or brain cells). Signals from these cells are often the drivers of the mood changes we mentioned earlier.

The vagus nerve is the main link between your digestive system and your brain. Signalling from the brain along the vagus nerve coordinates the digestive process and dysfunction in the nerve hinders communication. This can lead to an array of problems such as frequent indigestion, slow emptying of the stomach, heartburn, irritable bowels or weight gain.

Gut Brain

4. Chronic Inflammation

Inflammation is part of your body’s natural response to injury or infection. This is highly controlled by brain signalling along the nervous system and the vagus nerve is one of the primary pathways which signal to the brain the need for an inflammatory response.

The bi-directional communication both triggers the start of an inflammatory response and regulates the amount of inflammation that occurs. However when these neural circuits perform ineffectively, this can lead to excess inflammation. This in turn can lead to diseases such as arthritis and in extreme cases, as we have seen recently in the immune response to coronavirus infections, uncontrolled inflammation can become life threatening.

Studies show that stimulation of the vagus nerve can ease the suffering of arthritis and may help improve immune system health.

The body’s inflammatory response has been highlighted by a number of recent scientific and government reports as a primary driver in age related decline in health.

5. Difficulty swallowing

The vagus nerve plays an important role in the swallowing process. Although we take swallowing very much for granted, it requires a complex series of coordinated actions.

As you swallow a number of reflex actions occur which shut the nasal cavities and open the oral cavities, followed by esophageal contractions which push down into the stomach. The vagus nerve plays an important motor and sensory role in this process, working in concert with a number of other cranial nerves.

Dysfunction in the vagus nerve can make swallowing difficult and even dangerous. A small mistake can result in food passing into your lungs rather than your stomach. If this happens, impulses from the vagus nerve induce reflexive coughing to try to expel the food or drink from the lungs.

 

If you recognise any of the above issues, you may find great benefit from vagus nerve stimulation. Severe or sudden cases should always be discussed with a medical practitioner, but we all sometimes experience these changes to a greater or lesser degree. If they are mild but noticeable, simple lifestyle changes can help.

At vagus.net, we believe that electrical vagus nerve stimulation can help support these lifestyle changes. A growing body of recent science is showing that electrical treatments (sometimes called eletroceuticals) can in many cases be more effective than pharmaceutical interventions and carry almost no side-effects. However, electrical nerve stimulation shouldn’t be seen as a panacea. It shouldn’t be the only thing you do and it often works best when it’s used in conjunction with other lifestyle changes.

Improving vagal tone using direct electrical stimulation can often make it easier to engage in other activities, such as regular exercise and healthy sleep patterns, which in turn help strengthen vagal tone, leading to a virtuous cycle of better health.

Stay tuned for tips about other things you can incorporate into your life to improve vagus nerve health.

In previous posts we’ve pointed out that there is some evidence that the brain and body response to invasive and non-invasive vagus nerve stimulation appears to be very similar. Now scientists from Israel have added further evidence to support this idea. 

In a pre-print version of the paper published in the online biology research archive (bioRxiv) the three researchers reported on a study in which they tested participant response to transcutaneous vagus nerve stimulation (tVNS) using measures of pupil dilation and electroencephalography (EEG). The study found that tVNS applied to the ear resulted in robust pupil dilation (within a few seconds of trial onset) and modulated alpha wave EEG activity in the occipital lobe at the back of the brain. 

Importantly, these bodily responses are comparable to responses from invasive vagus nerve stimulation, indicating that non-invasive methods are a viable alternative in scientific research and in clinical applications; while obviously being far safer to administer. 

Previous studies have also shown that there are comparable responses, but this is the first to focus attention on pupillometry and ongoing EEG activity in the occipital lobe. Most other studies have focused instead on changes to reaction times which also show up in brain wave signals. 

The researchers noted that the measured responses between invasive and non-invasive vagus nerve stimulation were not completely identical however, speculating that this is due to slight differences in stimulation protocols. 

The auricular tVNS (sometimes abbreviated to taVNS) was also compared to sham stimulation. The sham did not elicit the responses observed in the non-sham stimulation, clearly indicating that the observations were elicited by the stimulation. 

Two common benefits of vagus nerve stimulation are that it usually leads to an improvement  in heart rate variability (HRV) and a drop in blood pressure (BP). Both these ‘biomarkers’ are important indicators of your long term health. 

Knowledge of the importance of maintaining a healthy blood pressure has been well known for a long time. A high BP is often referred to as the ‘silent killer’ because it can go unnoticed for a long time and is strongly associated with heart attacks and strokes. 

HRV is less well known, but more health practitioners are now emphasising its importance in long term health and well being. If you haven’t read our earlier post on HRV, that would be a good place to go either before or after you read this post. 

Improving your BP is all about following the health guidelines that we all know about: improving our diet, regular exercise, avoiding excessive prolonged stress and being well rested. Eating well and exercising is the sort of thing we can all do given a heavy dose of will power. I don’t want to dismiss how difficult that can sometimes be, but in some ways, it’s even harder for us to unwind at the end of our day, relax and get the proper kind of rest we all need to recuperate effectively. 

Our ability to effectively unwinding and relax can be greatly hindered if our parasympathetic nervous system is not working quite how it should be. The resulting fatigue then weakens the parasympathetic system further, creating a vicious cycle that simply exacerbates the problem. 

This is where following a protocol of vagus nerve stimulation can really help. tVNS has a direct positive effect on BP and HRV. We have previously written about the effect of tVNS on HRV and have pointed to recent research that has shown how beneficial it can be. In this post we’re going to take a look at it’s effect on the BP, so that you have some idea of what to expect when you start using the vagus.net stimulator. 

Blood pressure, like HRV, can vary a lot from day to day, or even within the same day. How your BP readings vary will depend on what you’ve eaten, how rested you are and how stressed you are. It’s important therefore to take readings over several days or weeks to get an overall picture. 

As an example, below are two graphs of blood pressure data from one of our test subjects -- a 65 year old woman in generally good health. 

The first graph shows her systolic and diastolic blood pressure readings over a ten day period. They are taken at roughly the same time every day in the early evening. The readings show a slightly elevated blood pressure, but nothing out of the ordinary for someone of her age. As you can see, the readings also vary a fair amount.

The next graph shows her readings over a ten day period when she began using our vagus nerve stimulator. The graph shows readings taken just before a 15min stimulation session and just after a stimulation session. The blue and orange lines show systolic and diastolic pressure before; while the red and green lines show readings after stimulation. 

The readings were all taken at roughly the same time each day, in the early evening.

As you can see, there is an overall fall in the BP trend (take note of the change in y-axis scale). It is not always the case that BP after stimulation is lower than BP before a session, but it is so on most occasions. 

There are two effects that are apparent here. The first is the immediate baroreflex. This is the most immediate way in which the body regulates blood pressure and involves the blood vessels dilating to rapidly reduce blood pressure. This mechanism is mediated by the vagus nerve, so stimulating the vagus has an immediate outcome. The second effect is the change in the trend. The overall blood pressure falls during the ten days of stimulation, which shows that the positive effects persist beyond the stimulation session. This is more likely due to an overall strengthening of vagal tone which allows the body to better regulate itself. 

Many people experience such falls in their blood pressure when they start tVNS. But don’t worry if you don’t. Everyone has a slightly different response to tVNS, some more dramatic than others. Studies show that those who have the most to gain usually see the greatest short term changes. But it’s important to remember that the real benefits of tVNS are very much in long term health outcomes. Developing regular, healthy habits will greatly improve your health over time. 

It isn’t essential that you measure your biomarkers. Many people simply find they feel better when they incorporate regular tVNS into their daily routines. And some will use it intermittently to reset their body’s equilibrium from time to time. All these ways of using tVNS can be effective.

However, if you’re one of those people who like to put numbers on things (like we are), we’d recommend that measuring your blood pressure will give a good indication of how you are responding to tVNS. 

In future posts we’ll take a close look at the mechanisms that bring about the changes that we tend to observe in blood pressure and heart rate variability.

References

[1] Ng, F. L., Saxena, M., Mahfoud, F., Pathak, A., & Lobo, M. D. (2016). Device-based Therapy for Hypertension. Current hypertension reports, 18(8), 61. https://doi.org/10.1007/s11906-016-0670-5

[2] Bretherton B, Atkinson L, Murray A, Clancy J, Deuchars S, Deuchars J. Effects of transcutaneous vagus nerve stimulation in individuals aged 55 years or above: potential benefits of daily stimulation. Aging (Albany NY). 2019; 11:4836-4857. https://doi.org/10.18632/aging.102074

[3] https://www.sciencedirect.com/topics/neuroscience/baroreflex

[4] Antonino D, Teixeira AL, Maia-Lopes PM, Souza MC, Sabino-Carvalho JL, Murray AR, Deuchars J, Vianna LC. Non-invasive vagus nerve stimulation acutely improves spontaneous cardiac baroreflex sensitivity in healthy young men: A randomized placebo-controlled trial. Brain Stimul. 2017 Sep-Oct;10(5):875-881. doi: 10.1016/j.brs.2017.05.006. Epub 2017 May 19. PMID: 28566194.

From Surgery to Skin

If you are on our website, you will very likely have heard something of the vagus nerve and how important it is to general health and well being. If you haven’t, you can look through our site or read some of our older blog posts to learn more about it.

Similarly, you may have heard of vagus nerve stimulation (VNS). Interest in VNS has grown with greater awareness of the nerve’s importance and there are now a range of techniques you can use. Some methods center around meditation and controlled breathing. Such techniques have roots in the ancient practices of meditation and yoga which are known to have significant health benefits.

Interest in electrical stimulation of the vagus nerve has grown in the last few decades. Initially, the medical application of this technique was both highly effective and highly invasive - involving major surgery to implant an electrical stimulator around the cervical (in the neck) branch of the vagus nerve.

Much more recently, interest has grown in non-invasive methods of VNS. This isn’t surprising, of course: invasive methods are expensive and carry considerable risks! All surgery is to some extent risky, but implanted VNS devices are also known to carry major side-effects:  these include changes to tenor of a person's speech and even complete loss of speech in some cases.

By contrast, much safer non-invasive methods of stimulating the cervical branch of the vagus nerve work by administering an electrical current from the surface of the skin that passes through a relatively thick layer of tissue (including skin, muscle and a tough arteria sheath), to stimulate the nerve. Electrodes are pressed against the neck, exactly where you would take your pulse and administered daily as when needed. This is obviously better than surgery, but scientists are still asking: are there even better ways to do this?

Safer and Easier

This has led scientists to increasingly become interested in stimulating the vagus nerve along it’s auricular branch - in the ear. At this location, the vagus nerve travels very close to the surface on the skin and has much less intervening tissue. What’s more, a growing body of research is  demonstrating that there are very similar physiological responses to stimulation at either location and between invasive and non-invasive stimulation. Therefore, stimulating at the ear is becoming a very attractive option.

Targeting stimulation at the ear is actually anything but novel. Humans have been doing it for millenia. Think of Chinese medicine and its emphasis on acupuncture. When I first heard of acupuncture as an undergraduate science major I didn't take it that seriously. I placed my trust firmly in modern science and medicine. But it turns out that the two are not mutually exclusive. Modern science is now providing strong empirical evidence for these ancient Eastern practices.

Knowledge of the passage of the nerves through the human body is usually obtained by the dissection of cadavers - bodies donated by people to the study of science. Over a few hundred years the art of dissection has steadily improved and with it the degree of intricacy of our knowledge of human anatomy.

Anatomical Knowledge

In 2002 two German medics dissected the ears of 7 cadavers (14 ears) to track the progress of innervation in the ear. This was an important event in the development of taVNS. It was the first attempt of its kind for almost a hundred years and remains the primary source of knowledge of the innervation of the ear. The study concluded that the cymba conchae and the tragus were the two primary locations that are innervated by the vagus nerve.

This year, in 2020, this anatomical knowledge was further extended by a group of Austrian scientists who used 3D episcopic imaging -- a method in which repeated slices of tissue are photographed and then weaved together to create a 3D model -- to further map the nerves and blood vessels in the human ear.

The image below is taken from the paper (click on it to view the original) which shows the kind of image produced by the scientific team.


The efficacy of this anatomical knowledge has since been tested extensively by scientists all over the world who have measured the effect of stimulating the auricular branch of the vagus nerve (ABVN) at both the tragus and the cymba conchae. These measures of physiological biomarkers can have either effects on brain function or bodily function.

The nerve fibres of ABVN are mainly afferent -- which means they are essentially sensory and carry information back to the brain. The ABVN travels back from the ear to a region of the brainstem called the medulla oblongata. This is a junction point between signals deeper in the brain and further branches of the vagus nerve that travel throughout the body. It is via this junction point that stimulation of the ABVN can have an effect directly on pathways in the brain as well as pass signals down to the visceral organs.

This means that scientists can examine the effects of ABVN stimulation using biomarker directly from the brain and biomarker that may come from the body.

Brain Biomarkers

Neurological changes can be picked up by brain scans. Using such techniques, scientists can see that stimulation of the ABVN has very similar effects to both invasive and non-invasive stimulation of the vagus nerve at the cervical branch (in the neck). Below is an image from an fMRI study of tVNS to help sufferers of tinnitus. Again, you can click on the image to look at the original study.


Using such techniques, scientists have built up an understanding of how stimulation influences the brain. Explaining how to interpret these images and finding is out of the scope of this post, but what the study, and many like it, show is that targeting the auricular branch of the vagus nerve activates certain regions of the brain. The important point I’m trying to make here is that there is clearly an effect from tVNS that is measurable.

However, though many of these studies are of great interest to science and to the development of specific treatments using tVNS, one of the main reasons for using tVNS is it’s broader, more general health benefits.

Body Biomarkers

With this in mind, a better way of monitoring the effects of tVNS at home is by using two bodily biomarkers: heart rate variability (HRV) and blood pressure. Both these can be measured using equipment that is broadly available and relatively cheap to buy. They are also highly correlated to long term health outcomes.

Blood pressure has long been termed by doctors as the ‘silent killer’. Having a high blood pressure puts you at much greater risk of heart attacks and strokes; and greatly reduces quality of life in old age.

For a long time, heart rate was the other important measure for general health. But more recently, medics have realised that heart rate varies a lot in the short term -- even between beats. And this heart rate variability (HRV) is a key measure of health with the same kind of predictive power as blood pressure. If you don't know much about this, you can read our earlier post to get some background.

Both these measures are highly correlated with good vagus nerve health. So improving vagal tone (the strength of activity in the vagus nerve) is one of the best things you can do to improve your long term health outcomes.

Vagus nerve stimulation is not the only way of improving your blood pressure or HRV. In a previous post we covered a number of changes you can make to your lifestyle. But tVNS is one option which can help achieve a better balance.

As we’ve covered before, recent studies by UK scientists have indicated that a few weeks of tVNS can greatly improve HRV. And both these biomarkers can be measured at home using readily available equipment. You don’t have to carefully measure them to benefit from using tVNS, but if you want to check up on how you are responding to changes in your lifestyle and habits, these biomarkers will give you good feedback.

In upcoming posts we will explore how to go about this and what to expect.

Researchers in Germany have been investigating the potential of using transcutaneous auricular Vagus Nerve Stimulation (taVNS) to help regulate our eating habits. In a study published in the Brain Imagine and Behaviour journal, scientists administered an hour of tVNS stimulation to a cohort of healthy participants and put them in an fMRI scanner to see how the stimulation influenced the appetite regulation centres of the brain. While not conclusive, the research showed some promising results. 

That stimulation of the vagus nerve could influence appetite makes a lot of sense considering that the vagus nerve is the primary channel of communication between our brains and guts; and also carries taste information back to the brain; and is highly involved in food metabolism. 

Moreover, patients who receive invasive forms of vagus nerve stimulation for the treatment of epilepsy or depression often experience appetite reduction and weight loss as a side effect. 

Motivated by such considerations, a team of researchers in two German Universities asked whether a form of non-invasive vagus nerve stimulation could be used directly as a means of controlling appetite. 

The researchers reported that the results of the study were promising, but mixed. Participants who received stimulation, as opposed to sham, found food less appealing after stimulation, but this did not translate into longer term changes in eating behaviour. 

Participants were tested with a combination of questionnaires and fMRI imaging. The researchers reported that the fMRI scans provided “clear evidence for specific modulatory effect of tVNS” on how appealing the participants found food and this neurological effect persisted beyond the stimulation session. But when eventually offered a meal, following a period of fasting, participants who received the stimulation ate approximately as much as those who received sham stimulation. 

The brain imaging showed very similar effects between invasive vagus nerve stimulation (VNS) and non-invasive stimulation (tVNS), as would be expected. And this was correlated in this study with self-reported appetite from the participants. 

The researcher suggested that with better stimulation parameters selection, the approach could be tuned to be more effective in the longer term and offer non-invasive treatment options for obese patients.

References

Alicart, H., Heldmann, M., Göttlich, M. et al. Modulation of visual processing of food by transcutaneous vagus nerve stimulation (tVNS). Brain Imaging and Behavior (2020). https://link.springer.com/article/10.1007/s11682-020-00382-8

Pardo, J. V., Sheikh, S. A., Kuskowski, M. A., Surerus-Johnson, C., Hagen, M. C., Lee, J. T., Rittberg, B. R., & Adson, D. E. (2007). Weight loss during chronic, cervical vagus nerve stimulation in depressed patients with obesity: An observation. International Journal of Obesity, 31(11), 1756–1759. https://doi.org/10.1038/sj.ijo.0803666.

Burneo, J. G., Faught, E., Knowlton, R., Morawetz, R., & Kuzniecky, R. (2002). Weight loss associated with vagus nerve stimulation. Neurology, 59(3), 463–464. https://doi.org/10.1212/WNL.59.3.463.

So you’ve received your kit and you’re excited about trying out your first session.

Getting started is very easy. Instructions are on screen and on the included card.

There is no one right way to do vagus nerve stimulation. As with everything, try things out to see what works best for you. Here are 10 tips and pointers to help you get the most out of your tVNS device:

1) You don't have to use the paste

Many people prefer not to. It’s a matter of choice. You can use the clip dry or with a little saline solution (salty water)

2) Make sure your skin is clean.

Skin is a living organ. It excretes a variety of fluids from salty sweat to lubricants and oils; and it picks up layers of dirt throughout the day. Your ears also contain waxes that can end up on the outer parts of the ear. And even the soaps and skin care products we use can leave a residue on the skin.

All of this can change the way you experience the stimulation session. The best thing to do is take a wet wipe, or simply some water on your thumb and finger and rub your tragus clean before you begin a session.

Skin contact

3) Attach the electrodes firmly.

It’s best to attach the electrodes as deeply onto your tragus as you can. You can either loop the wire over your ear or, even better, loop it over your right shoulder and run it behind your neck and then onto your left ear. Leave just enough length free to attach the clip at a comfortable angle. The weight of the wire is then either on your ear or on your shoulders and prevents the clip from dislodging during the session. This can be fiddly to begin with, but with practice, you’ll find it easy.

4) You may feel nothing at all.

Or, you may feel significant discomfort, such as pins and needles, which some people may find hard to tolerate. How people experience the stimulation varies greatly. Scientists don’t completely understand why this is, but it may be due to a number of reasons including your skin type and any residues that might be on the surface of your skin. Whatever the cause, the sensation you feel is because nerves in your skin are also triggered by the electrical current, which must pass through your skin to reach your vagus nerve. If you find the sensation hard to tolerate, try using the paste, or turning down the intensity. If, on the other hand, you feel nothing at all, you’re one of the lucky ones! In scientific studies, it is common to lower the stimulation level until the subject can barely notice the stimulation is active.

5) If it looks like it’s working, it probably is.

If the device is attached properly and showing a current, then the current will be flowing through your vagus nerve. If the electrodes cannot make good contact, the device will indicate this -- in which case, you should refer to tips 1-3 above. If the device shows current is flowing, read on.

6) The longer you use the device, the less you will feel.

This is because the nerves in your skin are designed to adapt and ignore sensations that last consistently over time. The nerve cells in your skin are designed to notice change and are more sensitive to new sensations. As you become accustomed to the sensation of stimulation, you will find it more tolerable until eventually you may barely notice it.

7) Never pull the clip off during stimulation.

Doing so could be very uncomfortable. It’s best to stop the session by pressing the button on the device before removing the clip.

8) 15 minutes is only a target.

Don’t stress if you don’t do the whole session. Many scientists currently recommend 15 minutes a day, but you can build up to this and you don’t have to do it all in one session. However, many people find stimulation works best if they allow themselves the full time to sit and relax during the stimulation session.

9) Side effects.

Thousands of scientific studies indicate that side effects are very rare, but not unknown. The most commonly noted side effects are actually skin reactions - these are typically classified as mild side effects and include tingling, pins and needles or some other skin discomfort; or warmth and redness on the skin at or around the point of stimulation. Side effects which are considered more serious are related to the actual stimulation of the vagus nerve. As the vagus nerve is also involved in a range of bodily functions, these more severe side effects can be very broad, including: indigestion, nausea, feelings of disorientation, changes in your hearing, neck stiffness or pains, or feelings of changes to the rhythm of your heart. These are nothing to be immediately alarmed about as even such rare occurrences have never been documented as long lasting. If you do experience any uncomfortable/severe side effects, you should stop the session, leave it for a few hours, or even a day or two and try again. If some of these more severe side effects persist, you may be one of a small percentage of people (around 1%) who do not tolerate tVNS well, and you should return the device for a full refund. We give a 30 day refund policy to allow plenty of time to find out if you are able to tolerate tVNS well or not.

10) Desired effects.

Vagus nerve strength (or tone) is known to correlate well with many long term health outcomes; in other words, the benefits of stimulation accrue gradually over time. Some of the benefits may be in terms of preventing or reducing the negative, natural and common effects of ageing. Shorter term benefits will be felt over a few weeks, and some very short term benefits may be measurable sooner. For example, straight after a session, blood pressure often falls and heart rate variability increases. These benefits may fluctuate with each session, but you should see an improving trend over time. It’s a good idea to keep track of these biomarkers (blood pressure and heart rate variability) if you can. Studies have shown that such benefits show measurable improvements within a few weeks. You may also feel other positive effects more immediately, such as a feeling of relaxation and wellness. Such effects are harder to measure precisely, but are often reported by users. Because of the subjectivity of such reports, these are hard to quantify. It may well be that positive effects reported by some people are the same effects that are reported as negative by others. Let your own feelings be your guide. Take things gradually and give it some time.

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Researchers have discovered that transcutaneous Vagus Nerve Stimulation (tVNS) administered to the auricular (at the left ear) branch of the vagus nerve can enhance language learning in adults.

 

The findings were reported this month by a team of scientists from the University of Pittsburgh and University of California, USA; and published in the Nature Partner Journal, Science of Learning

 

Llanos, F., McHaney, J.R., Schuerman, W.L. et al. Non-invasive peripheral nerve stimulation selectively enhances speech category learning in adults. npj Sci. Learn. 5, 12 (2020). https://doi.org/10.1038/s41539-020-0070-0

 

Their experiments were conducted on native English speakers who were exposed to Chinese Mandarin tonal categories while undergoing stimulation. A control group was exposed to the same language sounds without receiving the stimulation. The findings were supported by analysing brain signals using electroencephalography (EEG), which showed that the improved learning was facilitated by enhancing perception processing and memory consolidation. 

 

Experimental subjects who received the stimulation were able to learn new language sounds twice as quickly, in some cases, as those who received no stimulation. 

 

Adult language learners find it notoriously difficult to recognise non-native speech sounds and Mandarin is one of the hardest languages to learn for native English speakers because of its use of subtitle tones to change the meaning of words. 

 

Stimulation was delivered using a custom made earbud-like device. The researchers speculated that a similar approach might have further applications in other kinds of learning.


“Showing that non-invasive peripheral nerve stimulation can make language learning easier potentially opens the door to improving cognitive performance across a wide range of domains,” said lead author Fernando Llanos, PhD, a postdoctoral researcher in Pitt’s Sound Brain Lab.

 

tVNS has received considerable scientific attention in the last few years, but most of the previous studies have focused on the nerve’s central role in regulating bodily functions such as the functioning of major organs, maintaining nervous system balance (homeostasis) and the body’s inflammatory response. However the majority of the signalling along the auricular branch of the vagus nerve is actually afferent, meaning it is towards the brain. Some evidence has previously indicated that mood and cognition is positively affected by auricular vagus nerve stimulation in a much broader sense, but this is the first study that demonstrates such a direct link between stimulation at this location and an enhancement of a specific neurological function. 

 

The exact mechanism of how these benefits are incurred from tVNS are still not fully understood and more work is needed to explore this. It is possible that the effects are very specific and it will take the development of better stimulation protocols to improve and broaden the beneficial effects. 

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