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Psychology Today: Mindful Meditation and the Vagus Nerve Share Many Powers

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Psychology Today: Mindful Meditation and the Vagus Nerve Share Many Powers

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This morning, I noticed an exciting correlation between two new studies which separately identified that optimizing the functional brain connectivity of the default mode network (DMN) can have significant psychological and physical health benefits.

The first study found that stimulating the vagus nerve dramatically reduces the severity of depression. The second study found that mindfulness meditation also optimized functional connectivity of the default mode network which lowered inflammation and improved the brain's ability to manage stress and anxiety.

After reading dozens of new scientific studies over coffee this morning, I had an 'aha' moment when I realized that these two studies-both published in the current issue of Biological Psychiatr y-are using similar language to describe very different research.

Both of these studies offer holistic ways to optimize the functional connectivity of the default mode network using non-pharmacological interventions that have the power to improve psychological and physical well-being.
Non-Invasive Vagus Nerve Stimulation Can Significantly Reduce Depression
The first study used a new non-invasive vagus nerve stimulator (tVNS) to improve functional connectivity of the default mode network which reduced symptoms of major depressive disorder (MDD).

The February 2016 study, " Transcutaneous Vagus Nerve Stimulation Modulates Default Mode Network in Major Depressive Disorder," was published in Biological Psychiatry. This research was a collaboration between the China Academy of Chinese Medical Sciences and Harvard Medical School.

Patients with major depressive disorder who volunteered to participate in this study either received the new transcutaneous VNS or a 'sham' VNS, which served as a placebo. Then, they underwent a functional neuroimaging (fMRI) scan both before and after one month of treatment. When the researchers compared patients who received real or sham VNS, they found that the patients who received real VNS showed significant improvement of their depressive symptoms.

The real breakthrough of this new vagus nerve stimulator is that it's inexpensive and completely non-invasive. The device sits in the ear like a pair of headphones. Traditional VNS is a neurostimulation technique that has been used to alleviate treatment-resistant symptoms of depression. Typically, VNS is costly and requires potentially risky neurosurgery to implant the device.

In a press release, lead author Peijing Rong concluded, "This non-invasive, safe and low cost method of depression treatment can significantly reduce the severity of depression in patients and shows promise for future use."
Mindfulness Meditation Alters Default Mode Network Brain Connectivity
The second study identified that practicing mindfulness meditation improves the functional connectivity of the default mode network which lowers a biomarker for inflammation (Interleukin-6) while improving executive control and stress resilience.

The Carnegie Mellon University (CMU) researchers identified how mindfulness meditation optimizes brain connectivity and lowers stress. The fMRI brain scans from this study showed that mindfulness meditation training increased the functional connectivity of the participants' resting default mode network in areas directly linked to attention and executive control.

The February 2016 study, " Alterations in Resting State Functional Connectivity Link Mindfulness Meditation with Reduced Interleukin-6: A Randomized Controlled Trial," was published in Biological Psychiatry.

For this randomized controlled trial, 35 job-seeking, adults-who were experiencing the stress of unemployment-were enrolled in an intensive three-day mindfulness meditation retreat program or a well-matched relaxation retreat program that did not have a mindfulness component.

The participants who completed the mindfulness meditation program showed changes in brain functional connectivity and reduced Interleukin-6 which accounted for the lower inflammation levels. Participants who relaxed, but didn't practice mindfulness meditation, did not show similar outcomes.

In a press release, David Creswell, lead author and associate professor of psychology in the Dietrich College of Humanities and Social Sciences at CMU, said,

Mindfulness Essential Reads

"We've now seen that mindfulness meditation training can reduce inflammatory biomarkers in several initial studies, and this new work sheds light into what mindfulness training is doing to the brain to produce these inflammatory health benefits.

We think that these brain changes provide a neurobiological marker for improved executive control and stress resilience, such that mindfulness meditation training improves your brain's ability to help you manage stress, and these changes improve a broad range of stress-related health outcomes, such as your inflammatory health."

Conclusion: Mindfulness Meditation and Vagus Nerve Stimulation As a Dynamic Duo
The most exciting aspect of these studies is the prospect of combining mindfulness meditation with the new non-invasive vagus nerve stimulator to create a double whammy that leads to a wide range of psychological and physical health benefits.

Currently, I listen to an 'Om/Aum' playlist from iTunes when practicing my daily mindfulness meditation. I can easily see plugging in the new VNS headphone-like device while meditating to reap all the benefits of both mindfulness meditation and vagus nerve stimulation simultaneously.

Both of these studies offer inexpensive and effective ways to improve people's health without the use of pharmaceuticals or invasive surgeries. Stay tuned for more on the fascinating interconnections between the vagus nerve, mindfulness meditation, and the default mode network.

To read more on this topic, check out my Psychology Today blog posts,

© 2016 Christopher Bergland. All rights reserved.

Follow me on Twitter @ckbergland for updates on The Athlete's Way blog posts.

The Athlete's Way ® is a registered trademark of Christopher Bergland.

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Mindfulness Meditation and the Vagus Nerve Share Many Powers

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This morning, I noticed an exciting correlation between two new studies which separately identified that optimizing the functional brain connectivity of the default mode network (DMN) can have significant psychological and physical health benefits. The first study found that stimulating the vagus nerve dramatically reduces the severity of depression.

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Psychology Today: The Neurobiology of Grace Under Pressure

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Psychology Today: The Neurobiology of Grace Under Pressure

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When was the last time that you had to perform gracefully in a high-pressure situation? How did you handle it? Did you choke or did you have grace under pressure?

Researchers continue to confirm that daily habits of mindset and behavior can create a positive snowball effect through a feedback loop linked to stimulating your vagus nerve. In this entry, I will show you eight habits that stimulate healthy "vagal tone" and allow you to harness the power of your vagus nerve, so you can stay calm, cool, and collected in any storm.

Healthy vagal tone is indicated by a slight increase of heart rate when you inhale, and a decrease of heart rate when you exhale. Deep diaphragmatic breathing-with a long, slow exhale-is key to stimulating the vagus nerve and slowing heart rate and blood pressure, especially in times of performance anxiety. A higher vagal tone index is linked to physical and psychological well-being. A low vagal tone index is linked to inflammation, negative moods, loneliness, and heart attacks.

Heart disease is the number one killer in America. One way to improve your heart health is to focus on the vagus-friendly lifestyle habits I explore below. Well-conditioned athletes have higher vagal tone because aerobic breathing creates healthy vagal tone, which results in a lower resting heart rate. Healthy cardiac function is directly linked to stimulating the vagus nerve.

In 1921, a German physiologist named Otto Loewi discovered that stimulating the vagus nerve caused a reduction in heart rate by triggering the release of a substance he coined Vagusstoff (German: "Vagus Substance"). The "vagus substance" was later identified as acetylcholine and became the first neurotransmitter identified by scientists.

Vagusstuff is literally a tranquilizer that you can self-administer simply by taking a few deep breaths with long exhales. You can consciously tap the power of your vagus nerve to create inner-calm on demand. This knowledge alone should be enough to reduce the fear-of-fear-itself and give you grace under pressure next time you need it.
What Exactly is the Vagus Nerve?
The word vagus means "wandering" in Latin. The words vagabond, vague, and vagrant come from the same root. The vagus nerve is known as "the wandering nerve," because it has multiple branches that diverge from two thick stems rooted in the cerebellum and brainstem that wander to the lowest viscera of your abdomen touching your heart and most major organs along the way.

The vagus nerve is constantly sending sensory information about the state of the body's organs "upstream" to your brain. In fact, 80 to 90 percent of the nerve fibers in the vagus nerve are dedicated to communicating the state of your viscera up to your brain. When people say "trust your gut," they are in many ways saying, "trust your vagus nerve." Visceral feelings and gut instincts are literally emotional intuitions transferred up to your brain via the vagus nerve.

As with any mind-body feedback loop, messages also travel "downstream" from your conscious mind through the vagus nerve signaling your organs to create an inner-calm, so you can "rest-and-digest" during times of safety or to prepare your body for "fight-or-flight" in dangerous situations.

Your vagus nerve is the commander-in-chief when it comes to having grace under pressure. The autonomic nervous system is comprised of two polar opposite systems that create a complementary tug-of-war, which allows your body to maintain homeostasis (inner-stability).

The sympathetic nervous system is geared to rev you up like the gas pedal in an automobile - it thrives on adrenaline and cortisol and is part of the fight-or-flight response. The parasympathetic nervous system is the polar opposite. The vagus nerve is command central for the function of your parasympathetic nervous system. It is geared to slow you down like the brakes on your car, and uses neurotransmitters like acetylcholine and GABA to literally lower heart rate, blood pressure, and help your heart and organs slow down.

Unfortunately, the vagus nerve's reflexive responses can backfire and turn it from comrade into saboteur. Anytime you psyche yourself out before an important event, feel intimidated, or insecure your vagus nerve interprets that you are in real danger which exacerbates these negative responses.

All of the physical symptoms of performance anxiety-racing heart, sweaty palms, dry mouth, upset stomach, shakiness-are the result of your vagus nerve disengaging. Luckily, you have the power to harness your vagus nerve and keep it engaged to create grace under pressure. By understanding the incredible power of your vagus nerve you can begin practicing ways to flex its inhibitory strength to keep you mellow in times of distress.
8 Habits That Will Stimulate Your Vagus Nerve and Give You Grace Under Pressure 1. Visualize the Vagus Nerve
Visualizing the vagus nerve as a wellspring of neurobiological ingredients that create mental and physical calmness will create a self-fulfilling prophecy. This is not just the placebo effect in action. Remember, anytime you take a deep breath and exhale you are triggering a biological release of vagusstuff that will lower heart rate and blood pressure.

In addition to visualizing my vagus nerve, I literally talk to it in the third person like it is a separate entity. You can try this too the next time you have the butterflies or are shaky before a big presentation or challenge. I will literally say to my vagus nerve, "I thought we were in this together. I need you to work with me here. Come on! Don't let me down." Somehow this helps take my ego out of the situation, puts me at ease, and makes me feel like I have a loyal comrade on deck. Try this trick the next time you need grace under pressure and see if it works for you.
2. Practice, Practice, Practice
In a Psychology Today blog entry called No. 1 Reason Practice Makes Perfect, I wrote about the power of your cerebellum to store muscle memory and allow you to perform gracefully under pressure. Without extensive practice, we are forced to rely too much on the " executive function" of our prefrontal cortex. Anytime you "over-think" your performance you are more likely to choke, fumble, and drop the ball. Arthur Ashe called this "paralysis by analysis." Once the cerebellum is running the show, your vagus nerve engages, which helps create fluidity in your thoughts and actions.
3. Create Flow by Balancing Skill and Challenge
The key to being in the "zone" or creating a state of "flow" is to find the sweet spot where your skill level perfectly matches the challenge. Get in the habit of continually nudging against your limits. By increasing the challenge, gradually you become more skilled and comfortable with more difficult tasks.

Seek challenges that keep you nestled between anxiety and boredom. The key to peak performance is to have a heightened state of arousal but an inner sense of calm reflected in a perfect dynamic tension within the yin-yang of your autonomic nervous system.

Although it is tempting to bite-off-more-than you can chew, your vagus nerve can betray you if it feels you're in uncharted territory. By consistently increasing your skills, you will feel at ease as you take on bigger challenges. That said, if you ever do have the opportunity to leap frog to a high-stakes challenge, use other techniques here to harness the vagus nerve and use it as an ally to get you through.
4. Reframe Priorities and Values
I strongly believe that friends, family, good health, and generosity of spirit matter more than any achievements that requires grace under pressure. In 2006, Geoffrey Cohen, a professor at the Stanford University School of Education, conducted a series of experiments designed to reduce test-taking pressures. In the experiment, he asked students to write a paragraph about a topic unrelated to the exam such as: "relationships with friends and family," "religious values," "athletic ability," and "being good at art" before being tested. This brief writing assignment significantly improved the grades of students.

Before you face any challenge or test that fills you with performance anxiety, get in the habit of reframing the importance of the event by putting it in a broader perspective of other things that you're good at and what matters most to you. Even when the stakes are high, remember that every hurdle is an opportunity to learn. Mastery is a process. Overblown performance anxiety jacks up cortisol and adrenaline levels and makes you less likely to succeed.
5. Use Neuroplasticity to Re-Wire Habits of Positive Thinking
By generating positive emotions and a learned optimism, you will "fire-and-wire" together neural networks associated with a mindset that will give you grace under pressure. The vagus nerve picks up on signals coming from the "top-down" and from the "bottom-up," and uses these signals to re-wire your mind through neuroplasticity.

On January 28, 2013, researchers at the University of Glasgow in Scotland announced that they are hoping to help victims of stroke to overcome physical disabilities by helping their brains to "rewire" themselves using a Vagal Nerve Stimulator (VNS). Lead researcher Dr Jesse Dawson, a stroke consultant and clinical senior lecturer in medicine, described the vagus nerve by saying, "That nerve is one of the major nerves that goes to the brain. By stimulating the nerves, you can cause upstream changes in the brain without having to go into the brain."

It is hoped that the device will stimulate release of the brain's own chemicals and help the brain form new neural connections which might improve participants' arm mobility. In 2005, the FDA approved the use of VNS for treatment-resistant depression, although it's use remains controversial... VNS is also used to treat epilepsy and tinnitus.

Dr Dawson added: "Evidence from animal studies suggests that vagus nerve stimulation could cause the release of neurotransmitters which help facilitate neural plasticity and help people re-learn how to use their arms after stroke, particularly if stimulation is paired with specific tasks." The link between vagus nerve stimulation and neuroplasticity is strong. By focusing on creating healthy vagal tone you can trigger similar neuroplastic changes from the bottom-up. Creating a mindset of grace under pressure can be reinforced through the powerful mind-body connection of the vagus nerve.
6. Seek Daily Physicality
Cardio-respiratory activity, strength training and yoga stimulate vagal tone and harmonize hormones and neurotransmitters linked to grace under pressure. Aerobic activity stimulates healthy vagal tone due to the inherent diaphragmatic breathing of rhythmic cardio-respiratory exercise. Strength training with an emphasis on a robust exhale as you push the weight will stimulate vagal tone.

Yoga increases vagal tone, too. In a 2012 article published in Medical Hypotheses, researchers from Boston University School of Medicine (BUSM), New York Medical College (NYMC), and the Columbia College of Physicians and Surgeons (CCPS) presented evidence that yoga may be effective in treating patients with stress-related psychological and medical conditions such as depression, anxiety, high blood pressure and cardiac disease.

The researchers hypothesize that stress causes an imbalance in the autonomic nervous system (parasympathetic under-activity and sympathetic over-activity) as well as under-activity of the inhibitory neurotransmitter GABA. According to the researchers, low GABA activity occurs in anxiety disorders, post- traumatic stress disorder, depression, epilepsy, and chronic pain. The hypothesis advanced in this paper could explain why vagal nerve stimulation (VNS) works to decrease both seizure frequency and the symptoms of depression.

"Western and Eastern medicine complement one another. Yoga is known to improve stress-related nervous system imbalances," said Chris Streeter, MD, associate professor of psychiatry at BUSM and Boston Medical Center, who is the study's lead author. Streeter believes that "This paper provides a theory, based on neurophysiology and neuroanatomy, to understand how yoga helps patients feel better by relieving symptoms in many common disorders."
7. Anxiety is Contagious: Avoid Anxious People
As a neurosurgeon, my father needed to have grace under pressure. He understood how delicate the sensors of his own vagus nerve were and would ask anyone in the operating room to leave if he or she was emitting an uptight vibe.

I've learned to do the same in life-especially before an important event. Because anxiety is catching, I will remove myself from the vicinity of anyone who is negative, cynical or doubtful of my ability to hit-it-out-of-the-park in a high stakes situation. The vagus nerve picks up on people's vibe. Of course, none of us like to be around high strung people, but it is particularly important when you need to have grace under pressure.

If you are unable to remove yourself from anxious or nervous people (like in a waiting room for an audition or near the starting line of a race) I recommend using headphones with music that creates an appropriate mood and blocks the ability of others' anxiety to affect your vagal tone. You can also close your eyes and do mindfulness or meditation maneuvers to distance your vagal nerve from picking up the nervous vibe of people in your vicinity. Obviously, people who emit easygoing, warm, upbeat emotions are much better for your health, longevity, and ability to perform with grace under pressure. Seek these people out!
8. Foster Loving Kindness
In order to maintain healthy vagal tone, it's important to foster diverse and rewarding social connections. In a 2010 study published in Psychological Science, Barbara Frederickson and Bethany Kok of the University of North Carolina at Chapel Hill focused their attention on the vagus nerve.

Their article was titled: How Positive Emotions Build Physical Health: Perceived Positive Social Connections Account for the Upward Spiral Between Positive Emotions and Vagal Tone.They discovered that a high vagal tone index was part of a feedback loop between positive emotions, physical health and positive social connections.

Their research results suggests that positive emotions, positive social connections, and physical health influence one another in a self-sustaining upward spiral dynamic that scientists are just beginning to understand. Kok states that: "We propose here that people's ability to translate their own positive emotions into positive social connections with others may hold one of the keys to solving this mystery."

In the experiment Frederickson and Kok used a Loving-Kindness Meditation technique to help participants become better at self-generating positive emotions. However, they also found that simply reflecting on positive social connections and working to improve them also caused improvements in vagal tone.
Conclusion: The Vagus Nerve and Ferocious Equanimity
Equanimity is a core tenet of many ancient philosophies and religions. Equanimity is defined as "Mental calmness, composure and evenness of temper, especially in a difficult situation." Equanimity has its biological roots in the vagus nerve and is synonymous with grace under pressure.

Equanimity is not synonymous with passivity. As you strive to push yourself ever higher-and take on bigger challenges-do so with what I call " Ferocious Equanimity". Use your vagus nerve to stay balanced and calm when the stakes are high. As you push against your limits remember that your vagus nerve is always there to keep you imperturbable and steady on the high-wire act of living your life to its fullest and maximizing your potential.

Hopefully the advice herein will give you some tools to utilize the incredible power of your vagus nerve and give you grace under pressure the next time you need it.

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The Neurobiology of Grace Under Pressure

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When was the last time that you had to perform gracefully in a high-pressure situation? How did you handle it? Did you choke or did you have grace under pressure? Researchers continue to confirm that daily habits of mindset and behavior can create a positive snowball effect through a feedback loop linked to stimulating your vagus nerve.

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Know your inner saboteurs: Shirzad Chamine at TEDxStanford

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Your mind is your best friend. But it can also be your worst enemy. | Saboteurs

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How to Stimulate Your Vagus Nerve for Better Health

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How to Stimulate Your Vagus Nerve for Better Health

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Your mind is your best friend. But it can also be your worst enemy. | Resources

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Harvard: Calming Your Heart and Your Nerves

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Harvard: Calming Your Heart and Your Nerves

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It's that time of year when schedules somehow seem three times more full with work, school, and social gatherings, but the days seem shorter. On TV and in newspapers, articles appear weekly on ways to reduce holiday stress. Holiday cheer and spending time with family can keep us afloat during the holiday season, but when the holidays are over and life returns to normal, what happens when the stress doesn't melt as fast as the snow?

Due to economic changes and an increase in unemployment rates, many Americans have reported more stress over the last year. Frequent feelings of stress can get under our skin and damage our body. While stress does not contribute to ulcers, a popularly held belief, stress does have long-term effects on health. Stress has been linked to low immunity to common illnesses, depression, high blood pressure, and heart disease.

There are numerous stress reduction techniques that can help maintain health, such as diet, exercise, and relaxation. One ancient form of stress reduction is receiving renewed attention by health professionals. Transcendental meditation, once popular in the 1960s and 70s, is thought to have physiologic effects on the body that reduce the damaging effects of stress. The National Institutes of Health have spent over twenty million dollars on researching transcendental meditation and its possible effects on blood pressure, heart disease, and the immune system. While this is a small sum compared to other medical studies, research in alternative medicine is growing.

New studies involving Transcendental Meditation

Last month at the American Heart Association conference in Orlando, FL, researchers presented data on a nine-year study that looked at the effects of transcendental meditation (TM) on heart disease in a group of African-American patients with high blood pressure and heart disease. The study was a clinical trial that randomly assigned half of the 201 patients to practice TM twice daily while the other half received health education only. After nine years, 80% still practiced TM at least once per day and the data showed this group had 20 cardiovascular events (heart attacks, stroke, or death) compared to 31 in the group that received health education alone, a statistically significant difference. The two groups had similar lifestyle habits in terms of diet and exercise, but reported significantly less stress and had reduced systolic blood pressure by 5mmHg.

Several other recent studies have also examined the relationships between transcendental meditation and health outcomes. One study found TM decreased stress and blood pressure in college students. Another showed that older breast cancer patients significantly reduced their stress and improved their quality of life after practicing transcendental meditation twice daily.

While finding effective methods of reducing stress and risk of cardiovascular disease without the use of drugs is promising, these studies have been relatively small, and larger studies with a more diverse population are necessary to confirm whether transcendental meditation is indeed as powerful as these studies suggest.

Clearly, many individuals are benefitting from the technique. But how does meditation reduce stress and the risk of heart disease? First, we should understand how stress impacts our health.

How stress gets under our skin

We all experience stress at one time or another. There are different kinds of stress, and not all stress is negative. Acute stress is more immediate stress that we deal with in everyday life. Eustress, positive acute stress, provides us with energy when running a race or completing a deadline. It also causes the exhilarating feeling we get when doing things like riding a roller coaster or skiing down a steep slope. Negative acute stressful situations are those we tend to associate the word stress with: forgetting to study for a test, arguing with a friend or co-worker, or having a flight delayed due to bad weather. We may be stressed for a few minutes, hours, or a day or two, but eventually the problem is resolved and we return to a peaceful state.

The physiologic response to stress is controlled by the autonomic nervous system, the involuntary part of our nervous system that controls heart rate, blood pressure, and digestion. There are two branches to the autonomic nervous system: sympathetic and parasympathetic. The sympathetic nervous system prepares our body to react to stress ("fight or flight") and the parasympathetic helps us recover from stress ("rest and digest"). When we are stressed, our body releases chemicals that temporarily improve performance. Cortisol, adrenaline, and other stress hormones increase heart rate, slow digestion, and increase blood pressure, all to allow greater blood flow to our muscles, heart, and brain to be able to think or act quickly in the face of immediate or acute stress. The body is able to recover from acute from stress via a natural feedback loop with the brain. High levels of stress hormones in the blood signal to the brain to stop producing the stress hormones so we can rest and recover from the stressful event.

Sometimes stress can seem more like a way of life. Chronic stress is ongoing stress that seems endless, such as a demanding job, difficult family life, or experiencing ongoing hardship. This type of stress is the most damaging to our health. With acute stress, once the perceived threat has passed, the parasympathetic nervous system takes over, allowing us to relax and recover from the stressful event. But during chronic stress, the body is continually exposed to the hormones that regulate stress. The system's natural feedback loop is interrupted. The relaxation response is not activated, and the pathway that regulates cortisol is shut down, rendering it unable stop the effects of the stress. It is the constant activation of the stress response that leads to the negative health outcomes seen with chronic stress.

The primary stress hormones are cortisol, epinephrine (also called adrenaline), and norepinephine. Cortisol is a steroid hormone released from the adrenal glands, which sit above the kidneys. Epinephrine is also released from the adrenal glands. Norepinephrine is a neurotransmitter that helps the body and brain communicate with each other about stress and about how the body should react physiologically to stress. When cortisol is released in response to stress, it works with the other stress hormones to prepare the body to react to the stressful event. The breakdown of fat leads to increased blood sugar, helping to provide energy for the essential organs - brain, heart, and lungs (more on this later). Cortisol makes blood vessels more responsive to epinephrine and norepinephrine, and in turn these hormones constrict blood vessels to increase blood pressure. In addition, epinephrine acts to increase heart rate. Increased blood pressure and heart rate help deliver nutrients and oxygen faster to the organs that need them most. Acting together, stress hormones ensure that we can think and act quickly and clearly in stressful situations.

In addition to creating the emergency response, stress hormones also divert energy away from non-emergency functions like digestion, reproduction, and maintaining the immune system. For example, cortisol inhibits the immune system by preventing the production of T-cells, important players in the immune system, and by interrupting the distribution of other immune cells to the lymph nodes and bone marrow.

Because stress hormones suppress non-emergency functions, such as maintaining the immune system, chronic stress can leave many bodily systems at risk. Constant suppression of the immune system, for example, leaves us vulnerable to infections. Additionally, as mentioned above, to provide the body with extra energy to deal with stress, stress hormones stimulate the breakdown of stored fat into smaller fatty acids that we can use for short-term energy. These fatty acids, called triglycerides, enter the blood stream waiting to be taken up by our muscles to be used for quick energy if we need flee a stressful situation. This is likely an evolutionarily advantageous response to stress: earlier in time, stress probably meant running from a dangerous situation, and the free fatty acids gave our muscles energy. But if we don't use the fatty acids for energy through a physical outlet, the fatty acids remain in the blood, eventually causing high cholesterol. Thus, chronic stress leads to high blood pressure and cardiovascular disease, especially in combination with the stress hormones' direct effects on increasing blood pressure. When we have high blood pressure, our heart rate increases and blood flows more vigorously through our veins and arteries. Branch points in arteries can receive small injuries from the quicker flow of blood. The immune system then repairs arteries, but this process can lead to the deposition of plaque in the damaged areas. These little clots in our arteries block the free flow of blood, causing heart disease. Exercise is a great way to prevent this negative series of events: in addition to providing endorphins that makes us feel better, exercise uses the triglycerides in our blood stream so there are less to become trapped in our vessels as plaque.

As we can see, chronic activation of the stress response can lead to host of health problems. De-stressing and activating a resting state is important for maintaining proper balance between the sympathetic and parasympathetic nervous systems. Transcendental meditation may help to achieve this relaxation response.

Reviving Transcendental Meditation from the Vedas

Based on traditional Indian medicine, known as Ayurvedic medicine (ayus meaning life and veda relating to knowledge or science), transcendental meditation is thought to be one of the most widely practiced meditation techniques in the world. It originated over 5,000 years ago through the teachings of the Hindu god Krishna in the Bhagavad Gita; it was then lost and re-discovered several times throughout Indian history. In 1955, an Indian man named Maharishi Mahesh Yogi began teaching a style of meditation that later became known as transcendental meditation. Maharishi spent the 1950s and '60s traveling around the world sharing his meditation technique and other forms alternative medicine that emphasize the Ayurvedic values of mind-body balance. Maharishi trademarked Transcendental Meditation and Maharishi Vedic Approach to Health in the 1980s in the United States.

Transcendental meditation is described as spiritual - rather than religious - meditation, and the official Transcendental Meditation website (www.tm.org) describes transcendental meditation as a mental health relaxation technique. Formally, the technique is taught in a seven step course that includes both group lectures on the potential benefits and mechanistic explanations of TM, as well as individual instruction in meditation techniques. Transcendental meditation is supposed to be practiced for 20 minutes, two times per day. No chants are uttered aloud, nor is the individual taught to practice mantras; rather the technique is to focus on a specific thought to bring the mind's attention to that thought and away from the racing thoughts about the day's stressful events. The technique is designed to provide "restful alertness" and to bring the individual's thoughts to a peaceful level of consciousness, a quieter mental state. In medical studies involving transcendental meditation, all participants assigned to transcendental meditation received formal training by certified instructors.

The physiologic benefits of transcendental meditation do seem related to activating the parasympathetic and quieting the sympathetic nervous system. Medical studies have showed that individuals who practice transcendental meditation daily had lower blood levels of epinephrine, norepinephrine, and cortisol. Transcendental meditation also led to lower respiration rates and heart rate and better blood flow to the brain, indicating less constriction of blood vessels. A few studies have compared transcendental meditation to simple relaxation. One such study showed no difference and the other showed that the meditators had lower cortisol levels than then relaxers. In long-term studies, EEGs of individuals who practiced transcendental meditation showed significantly different EEG waves, indicating higher states of consciousness. Another study showed practitioners completed simple tasks more efficiently than non-meditators.

There are small, but concerning downsides to the transcendental meditation. Some earlier studies proclaiming the benefits of TM failed to report that the researchers had financial ties to the Maharishi Vedic Approach to Health. While more recent studies have disclosed associations with Maharishi's trademark, training in transcendental meditation is quite expensive. The course can be up to $1500 and requires travel to Iowa; experts in transcendental meditation claim it is not a practice that can be learned from a book or DVD. Some skeptics have gone as far as saying transcendental meditation is a scam and its practitioners cult-like.

Reviving transcendental meditation and bringing it in to the world of modern medicine may provide benefits to some individuals. However, more studies are needed to confirm the physiologic benefits. If it does prove to be as effective as promised, it is hoped that learning the technique will become more accessible and affordable. For now, perhaps the best way to reduce stress and its harmful effects is to exercise and take time out each day to practice some form of relaxation, whether it is meditation or simply allowing our minds to rest and not dwell on what keeps us feeling anxious. It may bring us better peace of mind and help restore balance in the autonomic nervous system.
-Megan Lee, Harvard Medical School

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Calming your nerves and your heart through meditation - Science in the News

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It's that time of year when schedules somehow seem three times more full with work, school, and social gatherings, but the days seem shorter. On TV and in newspapers, articles appear weekly on ways to reduce holiday stress.

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Dr. Chamine's Coaching Program Contact Info.

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Dr. Chamine's Coaching Program Contact Info.

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support@positiveintelligence.com.

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Shirzad Chamine: Confront Your Inner Judge

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John Williams - Finale (From "Star Wars: The Rise of Skywalker"/Audio Only)

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NEWS: Medical & Life Sciences - Researchers observe brain's responses to vagus nerve stimulation during sleep and wakefulness

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NEWS: Medical & Life Sciences - Researchers observe brain's responses to vagus nerve stimulation during sleep and wakefulness

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For the first time, researchers from the Institute of Bioelectronic Medicine at The Feinstein Institutes for Medical Research have characterized the brain's responses to vagus nerve stimulation (VNS) at various states of sleep and wakefulness. The new study, published in the journal Cerebral Cortex, adds to a growing body of research on the role of the vagus nerve in brain function and will also help health care providers to select optimal clinical practices of using VNS to treat diseases.

The vagus is a major nerve that runs throughout the body and controls crucial functions, like heart function and blood pressure, digestion, breathing and immune response. It also conveys sensory information to the brain about the current status of internal organs; a process termed interoception. The vagus nerve is a major therapeutic target for the emerging field of bioelectronic medicine, which uses neurostimulation to treat diseases. Electrically stimulating the vagus nerve is approved by the Food and Drug Administration as a non-pharmacological treatment for brain diseases, including epilepsy and depression. While the links between the vagus nerve, body and the brain are well documented, the effects of VNS on brain function are complex and only partially understood. Even less is known about the functions of the vagus in relation to sleep and wakefulness.

The study led Stavros Zanos, MD, PhD, assistant professor at the Feinstein Institutes, in collaboration with the University of Washington, who looked at the effects of VNS on brain activity in freely behaving non-human primates, both during hours of wakefulness and during their sleep. The researchers used a chronic vagus nerve implant and a wearable autonomous stimulation-and-recording device, the "Neurochip," to deliver VNS and at the same time record electrical brain activity in response to VNS through chronically implanted brain electrodes.

Vagus nerve stimulation holds tremendous potential to treat some of the most serious conditions, like Crohn's disease or pulmonary hypertension, but the question of which fibers of the vagus to stimulate and more importantly, when - like when the body is resting or active -- remains unknown. By observing and understanding the effects of VNS on brain function, we can create personalized, fine-tuned treatments for those diseases, whether they affect the brain or peripheral organs."

Stavros Zanos, MD, PhD, Assistant Professor, Feinstein Institutes

The team found that electrical stimuli to the vagus activates many brain regions within milliseconds and ultimately result in the stimulation of large populations of neurons in the cerebral cortex in the form of vagal-evoked potentials (VEPs). VEPs were seen in virtually every area of the cortex, indicating that VNS activates extensive areas of the brain. Importantly, those VEPs changed in shape and size throughout the day: They were smaller during morning/afternoon hours, when the animals were active moving, playing and eating in their cage, and larger in the evening, when the animals were asleep. VEPs were largest during a specific sleep stage called non-REM sleep, during which large, slow waves dominate the electrical activity of the sleeping brain.

Those findings suggest that the effects of VNS on brain function are largely modulated by the state of the brain at the moment the electrical stimuli to the vagus are delivered. This has implications about the interoceptive functions of the vagus nerve: sensory stimuli from peripheral organs may be received differently by the brain at different times of day. It also suggests that VEPs can be used as markers of engagement of vagal fibers to observe and tailor VNS treatment in individual patients.

"The brain monitors and controls healthy organ function because it receives and processes information in the vagus nerve," said Kevin J. Tracey, MD, president and CEO of the Feinstein Institutes. "Dr. Zanos' important research sheds light on how the brain processes these signals and offers new clues into how to advance bioelectronic medicine."

The Feinstein Institutes, the global scientific home of bioelectronic medicine, is a leader in this emerging field of medical research. Recently, Dr. Zanos and his team unveiled a long-term implant model for VNS in mice that successfully modulates heart rate and inflammatory proteins, changing how preclinical bioelectronic medicine research is conducted. And in October 2020, shares new research around a novel method to observe the effects of VNS by non-invasively measuring bodily responses.

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Researchers observe brain's responses to vagus nerve stimulation during sleep and wakefulness

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For the first time, researchers from the Institute of Bioelectronic Medicine at The Feinstein Institutes for Medical Research have characterized the brain's responses to vagus nerve stimulation (VNS) at various states of sleep and wakefulness.

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Breath of Life: The Respiratory Vagal Stimulation Model of Contemplative Activity

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Breath of Life: The Respiratory Vagal Stimulation Model of Contemplative Activity

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Institute of Psychology, Cognitive Psychology, Faculty of Social and Behavioural Sciences, Leiden University, Leiden, Netherlands

Leiden Institute for Brain and Cognition, Leiden University, Leiden, Netherlands

Contemplative practices, such as meditation and yoga, are increasingly popular among the general public and as topics of research. Beneficial effects associated with these practices have been found on physical health, mental health and cognitive performance. However, studies and theories that clarify the underlying mechanisms are lacking or scarce. This theoretical review aims to address and compensate this scarcity. We will show that various contemplative activities have in common that breathing is regulated or attentively guided. This respiratory discipline in turn could parsimoniously explain the physical and mental benefits of contemplative activities through changes in autonomic balance. We propose a neurophysiological model that explains how these specific respiration styles could operate, by phasically and tonically stimulating the vagal nerve: respiratory vagal nerve stimulation (rVNS). The vagal nerve, as a proponent of the parasympathetic nervous system (PNS), is the prime candidate in explaining the effects of contemplative practices on health, mental health and cognition. We will discuss implications and limitations of our model.

Introduction

The past 50 years have shown an increasing interest in eastern contemplative traditions in Europe and North-America. These traditions include meditation styles and mindfulness, as well as mind-body exercises like tai chi chuan (TCC) and yoga. What most of these practices have in common is not only their origin in eastern philosophy and religion, but also the goal to enhance individual physical and mental health. Scientific research has followed the popularity of contemplative activities (ContActs). Figure 1 shows that the cumulative number of relevant publications since 1945 follows a quadratic pattern, with total number of publications within a decade increasing from 2,412 between 1997-2006 to 12,395 between 2007-2016 (Web of Science, February 2018). The number of clinical trials on meditation, mindfulness, yoga, TCC or qi gong each year alone increased from a little under 20 in the year 2000 to about 250 in 2014, citations in the same timeframe going up from 20 in 2000 to 7,112 in 2014 (Web of Science, February 2018).

Figure 1. Cumulative number of scientific publications on contemplative activity (ContAct), from the 1945-1996 bracket to 2017 per individual year. Obtained from Web of Science in January 2018 using the search terms: "mindfulness" OR "meditation" OR "yoga" OR "tai chi."

The current article reviews scientific insights in potential health benefits. In particular, we investigate the role of particular breathing techniques (low respiration rate, long exhalations) integral to contemplative activities and show that these techniques are prime candidates in explaining the benefits of ContActs for health and mental health. Furthermore, we provide mechanisms and a neurophysiological model that can explain how respiratory patterns produce these effects; through vagal nerve stimulation.

Contemplative Traditions

For the purpose of this article we define contemplative activities as activities that involve conscious and attentive exercise aimed at changing one's mental state, contemplation in meaning comparable to "praying" and "meditating." We have deliberately not chosen the concept mindfulness because it is associated with particular practices, instructions and states, as we will discuss later. Despite the similarities between ContActs reflected in the definition, a few differences among ContActs are worth explaining here, because they are also used to position interventions in research.

The most common, the most referenced, the most studied and largest subgroup of ContActs is meditation. Most meditation traditions come from east and south Asia and are originally Buddhist or Hindu in nature. Zen Buddhist meditation (originating in China from a marriage of Buddhism and Taoism), loving-kindness meditation (Tibet), vipassana (India) and transcendental meditation (India) are popular styles. Yet there are also European and Middle-Eastern forms such as acem from Norway, Christian monastic traditions ( Egan, 1991; Studzinski, 2009) and Sufi Islamic meditation: muraqaba and whirling ( Cakmak et al., 2011, 2017; Nizamie et al., 2013).

In an attempt to classify meditation traditions according to their differentiated instructions, a distinction has been proposed between two types: focused attention meditation (FA) and open monitoring meditation (OM, Lutz et al., 2008; Lippelt et al., 2014). FA instructions emphasize attention to a particular focus, almost always the breath, along with means how to handle distractions and refocus attention. Zen meditation is commonly seen as an archetypical form of FA. OM stresses the spreading of attention on multiple endogenic and exogenic stimuli, having fleeting awareness of multiple sensory modalities, emotions and thought. Vipassana is popularly regarded as an exemplar of this style. There is no strict separation between the two types in zen and vipassana, and most traditions blend one style into the other. Overall, OM is frequently seen as a more advanced level exercise than FA, and is thus practiced more by experts as compared to novices.

In a further categorization attempt by Lutz and colleagues ( Dahl et al., 2015; for another three-dimensional classification, see Lutz et al., 2015), more meditation styles are classified based on their most emphasized and practiced techniques. The resulting framework has three meditation families: the attentional, the constructive and the deconstructive. Both FA and OM styles belong to the attentional family. The constructive meditations are aimed at improving the well-being of oneself and others, exemplified by compassion and loving-kindness mediation. The deconstructive practices focus on breaking habits of perception, affect, thought and behavior: most mindfulness meditation falls in this category. Note however, that the term mindfulness has been used in a different meaning as well. It refers not only to a category of meditative practice; it can also refer to a mental state, or even the ultimate enlightenment goal of these practices. As a mental state, mindfulness refers to a state of meta-awareness, in which the practitioner observes emerging feelings and thoughts without judgment ( non-judgmentality). The state of mindfulness can actually be the target of both FA and OM exercises.

Another subgroup within ContAct, here referred to as mind-body exercises, is more multi-modal. It involves both meditation and physical exercise; such as stances, positions, complex movements and muscle relaxation techniques. Common traditions are the many styles of Indian yoga and Chinese styles like TCC and qi gong. Origins of these styles differ, but most also have religious or mystical roots like meditation traditions, even when developed as a martial art (e.g., Taoism in TCC).

The Positive Effects of ConTact

Research has found a vast array of beneficial effects in the three domains of physical health, mental health and cognitive performance.

Physical Health

Cardiopulmonary Effects

Multiple reviews on different ContActs report a decrease in cardiometabolic risk factors and an increase in cardiopulmonary health and fitness, according to a meta-analysis this is most consistently reflected in lowered heart rate, blood pressure and blood lipid profile across practices ( Ospina et al., 2007). Reviews on separate practices confirm this for meditation styles such as mindfulness meditation and transcendental meditation ( Grossman et al., 2004; Walton et al., 2004), as well as the mind-body exercises yoga ( Büssing et al., 2012; Posadzki et al., 2014) and TCC ( Jahnke et al., 2010; Lan et al., 2013), where one meta-analysis indicates increased erobic capacity as well ( Taylor-Piliae and Froelicher, 2004). However, Cochrane reviews on transcendental meditation, TCC and qi gong state that even though there is suggestion to their positive effect, definitive conclusions on their efficacy cannot be drawn because of a lack of high-quality long-term trials ( Hartley et al., 2014a, b, 2015).

Anti-Inflammation

ContAct reviews also report immunological improvements; most studies find functional anti-inflammatory effects, where meta-analyses indicate that the most commonly reported decreases of pro-inflammatory markers are in C-reactive protein and pro-inflammatory cytokines, such as tumor necrosis factor-a ( Morgan et al., 2014; Bower and Irwin, 2016). Again, this enhancement can be seen with different ContActs: loving-kindness meditation ( Hofmann et al., 2011), yoga ( Black et al., 2013) and TCC ( Jahnke et al., 2010; Lan et al., 2013).

Physical Function

Like other physical exercises, mind-body exercises improve general physical function, most notably bone density, balance, strength and flexibility ( Jahnke et al., 2010; Büssing et al., 2012). Mindfulness-based stress reduction, yoga and TCC seem to ameliorate (chronic) pain conditions, as indicated by pain scales in conditions such as: migraine, fibromyalgia and osteoarthritis ( Grossman et al., 2004; Wahbeh et al., 2008; Büssing et al., 2012). As mindfulness-based stress reduction also includes yoga-like exercises, these results can be reserved to mind-body exercises and might best be interpreted as coming from the physical exercise part of these programs, as exercise-induced analgesia is well-established ( Koltyn et al., 2014) and is even comparable to medication in chronic pain conditions according to a review of multiple Cochrane reviews ( Geneen et al., 2017).

Mental Health

Stress Relief

Reviewed ContActs decrease stress and negative affect, and in parallel increase well-being and self-efficacy, as indicated by stress and (trait) anxiety rating scales and quality of life questionnaires ( Grossman et al., 2004; Kirkwood et al., 2005; Jahnke et al., 2010; Wang et al., 2010a; Keng et al., 2011; Eberth and Sedlmeier, 2012). Furthermore, a recent meta-analysis that collapsed studies using different meditation interventions, such as FA and OM, showed that they reduce multiple physiological stress markers across styles: heart rate, blood pressure, cortisol levels and inflammatory bodies ( Pascoe et al., 2017).

Stress-Related Psychopathology

ContActs, and notably mindfulness-based cognitive therapy, reduce symptoms in affective psychopathology ( Chiesa and Serretti, 2011; Kuyken et al., 2015). Most reviews and meta-analyses report decrease in symptoms of depression, anxiety disorders and post-traumatic stress disorder, as measured by structured clinical interview and common clinical scales, such as the Beck Depression Inventory ( Klainin-Yobas et al., 2012; Balasubramaniam et al., 2013; Chi et al., 2013; Cramer et al., 2013; Kim et al., 2013; Wang et al., 2013).

Cognitive Performance

Cognitive Control

Some studies show that ContActs enhance executive functioning and working memory or act as a buffer against age-related decline of executive functions and working memory: this applies to mindfulness meditation ( Zeidan et al., 2010; Gard et al., 2013), yoga ( Gothe and Mcauley, 2015; Luu and Hall, 2016) and TCC ( Wu et al., 2013; Wayne et al., 2014; Zheng et al., 2015). Most of the reported evidence for ContActs boosting executive functioning comes from cognitive inhibition tasks, such as the Stroop and flanker tasks, whereas the support for working memory improvement comes from span and n-back tasks. Furthermore, cognitive control states can be acutely affected through very short ContAct interventions ( Colzato et al., 2012, 2015a, b; Gothe et al., 2013), although these effects are typically smaller and less robust than following prolonged ContAct practice.

Attentional Control

ContActs also seem to have specific effects on attentional control and have been reported for FA and OM ( Shapiro et al., 2003; van Vugt and Slagter, 2014; Colzato et al., 2015a), mindfulness meditation ( Chiesa and Serretti, 2010; Eberth and Sedlmeier, 2012) and yoga ( Gothe and Mcauley, 2015), with most studies reporting enhancement effects on attentional network task components and the attentional blink. These effects are differentiable according to specific practices and can be in opposite directions ( Slagter et al., 2011; Hommel and Colzato, 2017). For example, practices high in FA are associated with better sustained attention, and those emphasizing OM support flexibility in allocation of attentional resources ( Lutz et al., 2009; van Vugt and Slagter, 2014; Colzato et al., 2015a). Jha et al. (2007) used the attentional network test ( Fan et al., 2005) to compare FA with OM in terms of attentional subcomponents as distinguished by Posner and Petersen (1990). Jha et al. (2007) showed that FA has its effects on the alerting component (detecting a stimulus) and OM on the orienting component (allocating attentional resources). Surprisingly, they found no differences on performance monitoring. Andreu et al. (2017), however, did find acutely enhanced performance monitoring by meditation. In people diagnosed with attention deficit hyperactivity disorder, meditation and mind-body exercises actually enhanced attentional functioning ( Rubia, 2009; Mitchell et al., 2015; Herbert and Esparham, 2017), although an earlier Cochrane review was unable to draw conclusions due to a lack of clinical trials ( Krisanaprakornkit et al., 2010).

Global Cognition and Creativity

Attention and control are not the only psychological outcome variables of ContAct research. Shapiro et al. (2003) observed enhanced creativity through transcendental meditation, while the meta-analysis of Ospina et al. (2007) indicated increased verbal creativity as the most reliable cognitive outcome of diverse ContActs. However, these acute effects can be in different and even opposing directions, as shown by a study on convergent and divergent thinking that used short FA and OM interventions ( Colzato et al., 2012). There is also evidence that global cognitive functioning, as measured by the mini-mental state examination or activities of daily living questionnaire is positively influenced by ContAct in aging populations with mild cognitive impairment or dementia. Studied ContActs include mindfulness meditation ( Eberth and Sedlmeier, 2012) and yoga and TCC ( Wu et al., 2013), as evidenced by a Cochrane review ( Forbes et al., 2013).

Effective Factors in ConTActs

As a first step towards explaining the highly overlapping effects of diverse ContActs on physical, mental and cognitive health, a straightforward approach is to analyze what they have in common. Three of the common factors we distinguish were also proposed by Hölzel et al. (2011b) for mindfulness mediation, but we formulate them in terms of activities rather than goals and propose three additional factors: attention training, affect training, metacognitive adjustment, body awareness training, physical exercise and the central addition: breathing techniques. The first three can be seen as forms of mental training and the last three as more embodied cognitive exercises. We will cover the first five factors and other proposed models before we introduce the breathing exercises.

Attention Training

The focus of attention in ContAct practices can involve many sensory or cognitive modalities; any of the external senses, the body, the breath, thoughts or feelings. Although explicit attentional training might be absent from some mind-body exercises, many ContActs are aimed at sustaining attention, handling distraction and refocusing or shifting and spreading of attention. These attentional techniques can explain the frequently reported effects on attention and perhaps some in the cognitive control domain. However, as stated earlier, these effects can be differentiated and in opposite directions according to specific instructions, showing increased sustained attention and decreased attentional flexibility by one manipulation (FA), and showing opposed functional differences by another (OM). Attention training in ContAct might thus be better described as resulting in a shift towards either more or less (attentional) control than as a unidirectional change. Both directions of change can be adaptive to the practitioner's intention because such metacontrol shifts result in either more persistence or more flexibility in thought ( Hommel, 2015; Hommel and Wiers, 2017). A limitation to the effective strength of attention training is that transfer of effects to other contexts and untrained skills is known to be rather limited ( Seitz and Watanabe, 2005; Green and Bavelier, 2012; Keshavan et al., 2014; Simons et al., 2016).

Affect Training

Exercises we define as affect training are aimed at removing or transforming negative emotions or moods. These start with becoming aware and paying attention to negative feelings or thoughts. This is comparable to exposure therapy ( Hölzel et al., 2011b). Subsequent instructions serve to modify the mental state. By decentering the meditator attempts to distance the self from the (negative) thought or feeling, trying to observe it as just a fleeting and subjective sensation, instead of a feeling that is taken personal, in effect trying to detach the observer from the observed ( Bernstein et al., 2015). Associated with decentering is the attempt to treat thoughts and feelings as not necessarily representing an objective reality. This is known as dereification. Finally, the detachment that results from decentering and dereification helps the meditator to avoid judgment about invasive and recurring thoughts, feelings or external events, such as surrounding noise. This non-judgmentality is also explicitly instructed. Taking these three mental exercises together, it is easy to maintain that they can help to reappraise negative feelings ( Hölzel et al., 2011b). Therefore, affect training, as comprising both exposure and reappraisal, could explain findings in the area of mental health, and possibly by extension, through (chronic) stress reduction: immune function and cardiovascular health.

Metacognitive Adjustment

Both the decentering and dereification techniques belong to the domain of meta-awareness and metacognition: being aware of awareness, thinking about thinking ( Flavell, 1976). By metacognitive adjustment practitioners try to change the way they process information. Many thoughts and perceptions follow a default processing route, resulting in a default interpretation and categorization of what is perceived. ContActs that involve thought monitoring try to identify and deconstruct fixed thought pattern, thereby deviating from this default processing route. This effect may transfer to daily life in the form of a tolerance for ambiguity and an increase in mental flexibility. As such, some forms of ContAct can be seen as executive function training, possibly transferring to situations where overruling pre-potent responses, ignoring irrelevant information, switching between tasks and rules, or keeping working memory up to date is relevant. Therefore, metacognitive strategies can explain beneficial effects of ContAct in the cognitive control domain. However, even apparently very similar cognitive training or gaming paradigms show very little transfer of training attentional control or working memory ( Green and Bavelier, 2012; Melby-Lervåg and Hulme, 2013).

Body Awareness Training

Exercises instructing for attention to different parts of the body, mostly to the skin and muscles, but also the viscera, make up the body awareness training factor. These could be mistaken as being part of the attention training factor. However, body perception is also uniquely central in affective processing and the sense of self ( Damasio, 2003; Ochsner et al., 2004; Araujo et al., 2013). Some researchers even theorize that body awareness is central in the cultivation of empathy ( Grossman, 2014). This makes us treat body awareness as a factor on its own. Kerr and colleagues ( Kerr et al., 2008, 2011, 2013; Kemp and Quintana, 2013) have shown that interoception can be enhanced in practitioners of mindfulness meditation and TCC: tactile acuity goes up, and activity in related somatosensory and visceral cortical areas (S1, insula, anterior cingulate cortex (ACC)) shows a pattern of increased attention to specific body parts on instruction and filtering of irrelevant somatosensory information. They state that metacognition and cognitive enhancement starts in the body: somatosensory exercises are in their view early versions of the techniques involved in attention, meta-awareness and metacognition. This being the case, body awareness could be involved in producing effects on emotional and cognitive levels.

Physical Exercise

One could argue that physical exercise is the most likely candidate for broad enhancement. Many studies provide evidence that physical exercise of different kinds (erobic, endurance, strength) is a strong cognitive control enhancer, resulting in better cognitive and response inhibition, and lower dual-task costs, though reviews on working memory performance are mixed ( Colcombe and Kramer, 2003; Smith et al., 2011; Roig et al., 2013; Voelcker-Rehage and Niemann, 2013; Voss et al., 2013; Berryman et al., 2014; Wong et al., 2015). Exercise is also generally accepted as a cardiovascular health booster ( Di Francescomarino et al., 2009; Heran et al., 2011; Korsager Larsen and Matchkov, 2016). However, the evidence for the supposed therapeutic effect of physical exercise on depression, anxiety and other stress-related conditions has been sparse, as indicated by a Cochrane review ( Mead et al., 2009), despite high expectations and invested resources ( Salmon, 2001). Most importantly, only a small minority of the reported ContActs provide any erobic or endurance exercise quality: the mind-body exercises, and perhaps to a smaller degree the mindfulness-based clinical programs (i.e., mindfulness-based stress reduction). This seems to rule it out as the prime candidate.

Theories and Models of ContAct Efficacy

There is a large gap between the amount of research done on ContAct and the number and amount of detail of models proposed to explain the benefits ( Schmalzl et al., 2015). (Neuro) cognitive models that have been put forward so far attribute the benefits of meditation to top-down factors such as attention and metacognition. For example, Vago and Silbersweig (2012) emphasized the role of the self in the effectiveness of mindfulness meditation, whereas Sperduti et al. (2012) highlighted the role of executive functions in all branches of meditation.

Models that describe the benefits of mind-body exercises ( Wayne and Kaptchuk, 2008; Gard et al., 2014; Clark et al., 2015) incorporate movement, mindfulness and attention. One refers to TCC as "meditative movement," clearly naming the two aspects of physical and mental training ( Larkey et al., 2009). However, despite labeling movement as a functional component, none of these models handle physical exercise as a full factor on its own. In the component "movement," exercise is reduced to motor coordination and skill learning, or the training of physical strength. Even though TCC is classified as mildly erobic ( Chang et al., 2010), the benefits of its erobic aspect are neglected. This is peculiar in light of the extensive support for the contribution of erobic exercise to physical health, mental health and cognitive performance.

Breathing Techniques

Two of the mind-body models also incorporate a factor that has been conspicuously absent from other models: breathing techniques ( Wayne and Kaptchuk, 2008; Gard et al., 2014). In both of these accounts, one on yoga and the other on TCC, the breathing type described as effective is slow, deep and diaphragmatic.

Effects of Respiration in Theory and Research

The breathing techniques used in ContAct include, but are not restricted to, slowing down respiration cycles, shifting to longer exhalations compared to inhalations, shifting the main locus of respiration from the thorax to the abdomen (diaphragmatic breathing), or paying attention to "natural" breathing. Especially slow and deep breathing with emphasis on long exhalation is dominant across traditions, including zen and vipassana-though there are a few practices stimulating faster respiration patterns (i.e., the yoga technique "breath of fire"). In the physically active mind-body exercises respiration can be synchronized with movement techniques; moving with the breath. For example, in some TCC styles moving towards the body is performed on inhale and moving outward on exhale. Note that in yoga, qi gong and TCC moving is performed slowly, and thus so is the breathing cycle.

Although the word breathing is frequently mentioned in the scientific literature on ContAct, this is almost exclusively done in a purely descriptive and not an explanatory fashion. Indeed, research on breathing as a ContAct mechanism is sparse, though there are concrete physiological grounds to look at breathing as an effective factor ( Brown and Gerbarg, 2005). As far as we know there are only a few articles looking at respiration in the context of ContActs directly, varying wildly in aims and measures. Danucalov et al. (2008) found increases in metabolism and oxygen uptake during yogic breathing exercises ( pranayamas) in experts, as compared to rest and meditation conditions in a within-subjects design. The breathing exercises used included holding the breath and extending exhalation. A similar slow breathing pranayama was used by Pramanik et al. (2009) showing reduced blood pressure and heart rate at post-measure. Brown and Gerbarg (2009) reviewed their own studies on the psychophysiological effects of various breathing techniques used in Sudarshan Kriya Yoga and reported a general tendency among the breathing exercises towards relaxation: activating the parasympathetic nervous system (PNS) and deactivating the sympathetic nervous system (SNS). Cysarz and Büssing (2005) observed increased cardiorespiratory synchronization with a slow breathing zen meditation intervention in naïve subjects. Though there is clearly a lack of studies on breathing in ContAct practice, fundamental neurophysiological studies on respiration mechanics and styles do abound.

In several studies respiration types have been manipulated in an attempt to influence autonomic nervous system functioning. A study of the effect of diaphragmatic relative to normal breathing on metabolism among male cyclists, before and after a meal found reductions in heart rate and glycemia, and increases in insulin ( Martarelli et al., 2011). Bernardi et al. (2001) induced hypoxia in participants and found that slow breathing exercises not only increased blood oxygenation, but also down-regulated SNS activity. Similar results are reported by Critchley et al. (2015) study on hypoxia. Many other studies show that slow and diaphragmatic breathing increases PNS activity, as measured by blood pressure, heart rate or heart rate variability (HRV; Hirsch and Bishop, 1981; Lee et al., 2003; Pal et al., 2004; Lehrer and Gevirtz, 2014; Van Diest et al., 2014; Mortola et al., 2015; Perciavalle et al., 2017; Tavares et al., 2017; for some conflicting results see and Montgomery, 1994; Conrad et al., 2007). In sum, experimental slowing of respiration seems to shift the balance between SNS and PNS activity towards the latter. Next, in light of these findings, we will look at the part of the nervous system responsible for such a shift: the vagus nerve (VN) and measures of its tone (i.e., HRV).

The Vagus Nerve and Heart Rate Variability

Vagus Nerve

The autonomic nervous system ( Langley, 1903) is a dual-system divided in the SNS and PNS with mutual inhibitory connections, though the dual innervation can also work complementary in organs such as the heart ( Jänig et al., 1983; McCorry, 2007). The SNS is responsible for the fight/flight mode of organisms. It raises heart rate, blood pressure and indirectly respiration rate. It dampens currently irrelevant homeostatic processes, but stimulates immediate availability of energy. The PNS acts as an opposing force. It is the rest/digest system of the organism. It lowers heart rate, respiration rate and increases digestion. The VN is the main affector and effector of the PNS.

Cardiopulmonary Control

Anti-Inflammation

There is evidence that VN also influences physical health by suppressing inflammation. An anti-inflammatory reflex, known as the cholinergic anti-inflammatory pathway has been put forward from findings in animal studies on rats ( Tracey, 2002, 2007; Pavlov and Tracey, 2015). This response is thought to inhibit a cascade of inflammatory activity and is triggered by vagal afferents monitoring immune status. However, an alternative sympathetic anti-inflammatory reflex has been proposed, explaining conflicting results in rat studies: the splanchnic anti-inflammatory pathway, where VN plays an afferent role at most ( Bratton et al., 2012; Martelli et al., 2014a, c, 2016). A complete discussion of these competing pathways lies outside the scope of this review. Suffice it to say that the VN seems to be involved in anti-inflammation in humans: studies using VN stimulation paradigms report anti-inflammatory effects as well ( Browning et al., 2017; Johnson and Wilson, 2018). Furthermore, after vagotomy inflammatory activity goes up. This resembles the earlier mentioned tonic inhibition on heart rate ( Borovikova et al., 2000). This merits the proposition that VN mediates effects of ContAct on immunological health, specifically anti-inflammatory, and potentially those on auto-immune diseases.

System State Monitoring

Clearly, these functions all move the system towards the rest/digest mode of operation and away from fight-or-flight. Not only does VN control heart rate and slow deep breathing, slow respiration rates with extended exhalation could also activate the PNS by VN afferent function in the airways. This is a form of respiratory biofeedback. Slow breathing techniques with long exhalation will signal a state of relaxation by VN, resulting in more VN activity and further relaxation. Though VN involvement can explain effects on health and mental health, the link with cognition is less clear. One of the links between respiration and cognition is HRV.

HRV

Vagal Tone

HRV, the fluctuations in beat-to-beat intervals of the heart, has been related to VN and some measures are believed to reflect "vagal tone." As only the VN cardiac output and not the sympathetic innervation would be able to produce rapid changes in heart rate. HRV is used as an indicator for individual physical conditioning, general health, reactivity to and recovery from high stress levels. Higher HRV is related to lower stress levels, better health and disease outcomes ( Thayer et al., 2012). A frequently used HRV metric to assess vagal tone is the respiratory sinus arrhythmia, by some maintained to be the best reflection of vagal tone ( Porges, 2001, 2007). This refers to the acceleration of heart rate during inhalation and deceleration during exhalation.

As stated earlier, HRV is regarded as an indicator of physical, but also cognitive health. Indeed, there is a concrete link between HRV and cognition, first sketched in the neurovisceral integration model of Thayer and Lane (2000).

HRV and Cognition

The neurovisceral integration model ( Thayer and Lane, 2000; Thayer, 2007; Thayer et al., 2009) posits bi-directional cortical influences on autonomic functioning and integrates CNS and autonomic functioning. It builds on the work of Benarroch (1993, 1997) on the Central Autonomic Network (CAN), a network of brain areas for goal-directed behavior involved in modulating the viscera. These areas are mostly limbic and include the insula, ACC, amygdala and hippocampus. The neurovisceral integration model extends this to prefrontal structures (orbitofrontal, medial and lateral PFC). These regions are able to influence HRV and initiate endocrine responses through the VN. But the integration of CNS and autonomic nervous system also works bottom-up: projections from VN afferent medular termini reach limbic and cortical regions, affecting cognitive control. This framework provides a basis for a connection between executive functions on the one hand, and body relaxation on the other. Indeed, studies by Thayer and others show evidence of a positive association between HRV and PFC activity and subsequent improvements in executive functions, notably cognitive inhibition. PFC seems to exert tonic inhibition on heart rate (and the amygdala), and greater activity of the PFC is associated with higher HRV ( Lane et al., 2001, 2009). Hansen et al. (2003, 2004) provided further evidence of this relation in individual differences studies: higher HRV is associated with better executive functions and working memory performance. In the view of Thayer and colleagues, HRV can be seen as a peripheral index of the adaptability of the nervous system and thus the organism. HRV increases with goal-directed behavior and emotion regulation, and reduced HRV is indicative of cognitive stress. Clearly, the CAN and these experimental findings give grounds for explaining executive function enhancement following ContActs as originating from VN, through upward projections producing functional and structural changes in the executive network.

In a recent update of the neurovisceral integration model ( Smith et al., 2017), which adopts a hierarchical network architecture, the relative weight of top-down and bottom-up influences can be adjusted. This leaves room for learning or the training of autonomic responses. For example, a non-adaptive dysfunctional stress response can be modulated or go extinct by the reappraisal of threat (top-down) or exposure to the stressor (bottom-up). This means that stress levels could be downregulated by lower level state feedback that is associated with unthreatening situations. In our account these are the pulmonary parameters: low respiration rate and long exhalation.

Vagal Nerve Stimulation

The many functions of VN have led researchers and clinicians to develop electrical or behavioral intervention techniques for VN stimulation (VNS). These techniques are promising for clinical application and for improving cognitive performance. At the same time, the pattern of results observed following VNS mirror those obtained by ContAct, making VN involvement likely, and thus breathing exercises a promising candidate for stimulation.

Electrical VNS

Electrical VNS ( Henry, 2002; Groves and Brown, 2005; Yuan and Silberstein, 2016b) was originally used to treat epilepsy. However, because it also increased the mood of stimulated patients it found its way as an approved therapy for depression ( Johnson and Wilson, 2018), especially treatment resistant depression ( Müller et al., 2018). It is also used to treat cardiovascular disease ( Das, 2011; Johnson and Wilson, 2018) and as mentioned earlier, VNS has also shown acute anti-inflammatory effects ( Browning et al., 2017; Johnson and Wilson, 2018), possibly through the anti-inflammatory pathway ( Borovikova et al., 2000; Yuan and Silberstein, 2016c).

VNS is also applied to respiratory conditions. A study on guinea pigs has shown that strength of stimulation makes a difference: high voltage produces the predicted VN effects bronchoconstriction, reduced heart rate and blood pressure, while low voltage only produces the pulmonary effects ( Hoffmann et al., 2012). Studies in humans, in contrast, show that VNS can actually produce airway relaxation in asthma patients during acute episodes, as indicated by an increase in forced expiratory volume ( Miner et al., 2012; Steyn et al., 2013). In other words: stimulating afferent branches of VN during exacerbations (shortness of breath) produces longer exhalations and therefore slowing of respiration rate.

Transcutaneous VNS

Few studies have been conducted using tVNS to influence cognitive behavioral performance. However, two studies have shown phasic changes in associative memory ( Jacobs et al., 2015) and in response selection ( Steenbergen et al., 2015) following tVNS. Interestingly, tVNS also causes effects that would be expected if VN efferent function would be modulated, by increases in vagal tone. Multiple studies and reviews show an increase of PNS activity, and some also show a decrease of SNS activity ( Popov et al., 2013; Clancy et al., 2014; Murray et al., 2016; Zhou et al., 2016). Furthermore, tVNS is also associated with anti-inflammatory effects ( Wang et al., 2014, 2015). These results overlap strongly with those obtained in ContAct studies.

Behavioral VNS

There are also behavioral forms of VNS ( vagal maneuvers), which are supposed to stimulate VN bilaterally. The Valsalva technique; pinching the nose closed and then trying to exhale through the nose, is best known for returning normal pressure to the inner-ear cavities when changing altitudes ( Arnold, 1999). It is initiated by flexing the abdominal muscles and extending exhalation (in clinical or laboratory setting by blowing into a balloon), showing a strong similarity with breathing techniques in ContAct. Even further, extending, slowing and holding respiration are all considered vagal maneuvers on their own, stimulating the VN. All of these vagal maneuvers have been shown to slow heart rate (bradycardia). We propose that the breathing exercises of ContAct might be seen as a form of behavioral VNS.

Overviewing the functions and applications of VN, one can see its potential as a mediator between respiratory patterns employed in ContActs and the reported effects on health, mental health and cognition. This will be further outlined in our model.

The Respiratory Vagal Stimulation Model of Contemplative Activity

The model, as depicted in Figures 2A-D, has a number of assumptions, inductions and predictions. These can be roughly divided into: (a) ContAct breathing; (b) respiratory stimulation; and (c) long-term effects. This will be followed by a definition of terms and measures.

Figure 2. Panel (A) represents an overview of the respiratory vagal nerve stimulation (rVNS) model of ContAct. See the text body for more details. There are two pathways through which respiration style stimulates VN: direct and indirect (biofeedback through afferent projections), shown in (B,C) respectively. (D) The tonic changes in the networks and the long-term effects. Color coding: red = VN, blue = other anatomy, purple = physiology, green = function, dark blue = direct route, orange = indirect route. Arrow-ends represent role: triangle = activating or increasing, circle = deactivating or decreasing, bladed = structural increase, ellipsis = structural decrease, diamond = afferent. Numbers on lines represent the temporal sequence during stimulation and the thickness of lines the phasic relative synaptic weight of the connection as a result. The dashed line represents the hypothetical afferent pathway of the thoracic/abdominal ratio to VN. RR, respiration rate; I/E, inhalation/exhalation ratio; T/A, thoracic/abdominal respiration ratio; HR, heart rate; HRV, heart rate variability; INF, inflammation state; SNS, sympathetic nervous system; HPA, hypothalamic pituitary adrenal axis; CAN, central autonomous network; DMN, default mode network.

ContAct Breathing

ContActs are multi-modal interventions that can incorporate many different techniques and instructions. However, one of the most prominent and common ContAct techniques is respiratory regulation, in other words: breathing exercises. These breathing exercises have in common the instructions to focus on and slow down respiration, and/or extend exhalation. In Figure 2 this is represented by the node "breathing regulation" inhibiting the nodes for respiration rate and inhalation/exhalation ratio, in other words: these exercises lower respiration rate and ratio. However, even exercises where the breath is just an attentional focus will lead to non-volitional adjustments of respiration. Practitioners just being aware of their breath enter slower and deeper respiration cycles. This can be caused by individuals' previous experience with slow and deep breathing techniques, whose respiratory patterns will be automatically superimposed on current respiration. Another way is through the commonly slow pace of guided meditation instructions themselves: practitioners will sync their respiration to this rhythm. As focusing supposedly also leads to respiratory adjustments, similar to the breathing exercises, this is fit in the model overview (Figure 2A) by the node "breathing focus" showing a dashed line towards the node "breathing regulation." Frequently adopting these respiration patterns (slowed and with longer exhalations) can explain a significant part of the efficacy found within ContAct practice. Though the ContActs are diverse, they have shown a similar pattern of beneficial effects on health, mental health and cognition: mostly in stress-related conditions and performance. This pattern can be explained by these controlled breathing exercises.

Respiratory Stimulation

Direct Route

As can be seen in the dark blue path in Figure 2B, adopting a low respiration rate and small inhalation/exhalation ratio can directly stimulate VN, top-down from the executive network, by its own efferents (connections 2). This phasic increase in vagal activity increases reactive HRV, lowers heart rate and blood pressure (also by cardiorespiratory coupling), inhibits the SNS and indirectly the hypothalamic pituitary adrenal axis, and potentially activates an anti-inflammatory pathway (connections 3), resulting in a decrease of acute stress levels (connections 4). Critically, we also posit that VN activation statically increases cognitive control through CAN projections (connections 5).

Indirect Route

Indirectly, afferent VN pathways constantly signal respiratory patterns upwards, in this case characterizing a state of relaxation and low-threat. As a result, efferent VN activation further increases vagal tone and produces associated physiological consequences (e.g., lowering heart rate, blood pressure, increasing HRV); a loop of relaxation ensues. In Figure 2C this route is represented by orange diamond arrows (afferent) that signal on respiratory patterns, possibly including the ratio of thoracic and abdominal expansion (connections 1), and the cardiac patterns influenced by the direct route (connections 2). This relaxed body state goes up from VN to the limbic system (connections 3), that in turn re-activates VN (connections 4), increasing its excitatory weight on cardiac and inflammatory patterns of physiological acute stress (connections 5 and 6) and statically enhances cognitive control (connections 7). The indirect route can be seen as a form of biofeedback and is responsible for long-term changes in vagal tone. In this the respiratory patterns play a key role: a recent study using electroneurogram to map respiratory pattern signaling of the left VN, showed a near perfect overlap between this mapping and actual respiratory cycles ( Sevcencu et al., 2018). Note that the left afferent VN is the locus of (t)VNS.

Diaphragmatic breathing might provide rVNS independent of respiration rate and inhalation/exhalation ratio, represented by the dashed inhibitory path of the thoracic-abdominal ratio to VN in Figure 2C. When oxygen demand is high during exercise or stress, SNS becomes active, and thoracic respiration goes up, and abdominal muscles are actively inhibited ( Secher and Amann, 2012). When oxygen demand is low, in times of rest and digest, the vagal dominant state, the ratio shifts more towards abdominal respiration. The abdominal-thoracic respiration ratio of the rest-and-digest mode of the PNS should thus be similar to the ratio during ContAct practice. rVNS produces a wide range of effects in health, mental health and cognitive flexibility of the practicing individual, in the short as well as the long-term.

Long-Term Effects of Respiratory Stimulation

Stress Reduction and Anti-Inflammation

Cognitive Performance

rVNS increases vagal dominance in both resting state and in active states demanding behavioral and cognitive flexibility. The CAN ( Benarroch, 1993) is a CNS network that receives its projections from VN and overlaps with the executive functioning network. The executive functioning network is not only dependent on autonomic balance for proper functioning, but can also be functionally and structurally changed by CAN activity. Enhancement of executive functions in ContAct practice results from rVNS of CAN, by structurally changing and activating the hubs of the executive functioning network and increasing their connectivity. In Figure 2D this is represented by the bladed red arrow path going up from VN to the limbic system to the executive network and then to the executive function node. Likewise, we hypothesize that default mode network (DMN, Raichle et al., 2001) hubs and internal functional connectivity are decreased, while DMN connectivity with the executive network is increased. The role of the DMN can be visualized as being inhibited by vagal projections and having a two-way inhibitory pathway with the executive network, as represented in Figure 2. These pathways are activated both phasically (Figures 2B,C) and tonically (Figure 2D).

Terms and Measures

1. Different forms of volitional control of respiration are defined as controlled breathing techniques. For this definition to be valid it should be possible for humans to put respiration under volitional control, overriding central pattern generated drive, and this has indeed proven possible for the diaphragm ( Kolář et al., 2009).

2. Vagal tone is a construct relating to intra-individual tonal levels of PNS activity. Vagal tone can indirectly be indexed using HRV, notably respiratory sinus arrhythmia.

3. Vagal dominance refers to a relatively higher activity of PNS over SNS. Vagal dominance (PNS hyperactivity and SNS hypoactivity) should be observable in physiological measures of PNS (i.e., HRV) and SNS (i.e., pre-ejection period, skin conductance, cortisol) activity. Vagal dominance can be increased both in acute and chronic time settings ( Porges, 2001, 2007). However, in this work it is defined as a macro-state of autonomic balance, spanning minutes and hours, not a micro-state, changing millisecond to millisecond, for example: in heart node activation.

4. HRV is also a suitable inverse measure of acute and chronic (psychological) stress ( Porges, 1992, 1995). HRV can be used as an indirect indicator of intra-individual and possibly inter-individual differences in executive functions ( Thayer et al., 2009).

5. As rVNS is a form of VNS, results obtained from studies using other modes of VNS should resemble those from ContAct studies in similar conditions, although not necessarily with perfect overlap.

6. The stress release refers to stress responses over larger scales of time; not the acute adaptive arousal employed in challenging situations, but the perseverative and chronic kind; in other words: the default stress response ( Brosschot, 2017).

rVNS: Evidence and Possible Mechanisms

What evidence is there for respiration as a mode of VNS? In our model there are two ways respiration can stimulate VN: directly and indirectly. In the direct route, slow breathing and extended exhalation are caused by vagal activity. This follows from the previously mentioned role of VN in respiratory affective and effective processing (slowing and exhalation). Controlled breathing in this form thus uses the vagal nerve as effector and increases its activity volitionally, if only momentarily. The indirect route involves stimulation through biofeedback and follows from physiological feedback theory: by adopting physiological body patterns associated with relaxation and low threat situations (i.e., slow breathing) vagal afferents project this state to the CNS, which interprets this as a reflection of the current contextual threat level, and proceeds by further adopting a rest-and-digest state top-down, again through VN. The indirect route is responsible for more long-term tonic changes of vagal tone. By either route, breathing styles with low respiration rate and low inhalation/exhalation ratio should show increases in vagal tone, though in slightly different timeframes ( Keyl et al., 2001).

Evidence

Most experimental studies show higher HRV following breathing instructions, consistent with the involvement of rVNS. In particular, there is ample evidence that slow and deep breathing increase HRV indices of vagal tone ( Hirsch and Bishop, 1981; Pal et al., 2004; Larsen et al., 2010; Lehrer and Gevirtz, 2014; Critchley et al., 2015; Mortola et al., 2015; Tavares et al., 2017) and lowers stress markers such as: heart rate, blood pressure and salivary cortisol ( Lee et al., 2003; Pramanik et al., 2009; Perciavalle et al., 2017). Van Diest et al. (2014) looked specifically at the effects of different inhalation/exhalation ratio at either slow or normal respiration rate on different HRV measures (peak-valley, HF): higher HRV (both measures) was reported in the slow respiration condition, but only for extended exhalation, inhalation/exhalation ratio: 0.24, and not for extended inhalation, inhalation/exhalation ratio: 2.33. Though normal ratios were not included, this study most clearly shows the stimulating effects of the specific respiration styles on VN. For another example of extended exhalation, albeit with a completely different aim and context: a study on native American flute playing showed significant increases in HRV during playing, contrary to what one would expect during exerting activity ( Miller and Goss, 2014). It needs no mention that playing any piping instrument involves extreme extended exhalation.

As far as we know, few studies report a decrease in HRV after controlled breathing, and these are primarily found outside the domain of ContActs. Sasaki and Maruyama (2014) gave instructions to participants to "control breathing," without emphasizing a particular style (rate or ratio), and compared that to spontaneous breathing. This resulted in lower HRV, which may be the result of an increase in mental effort, stress, and thus SNS activity. Indeed, earlier reports also show a decrease of HRV when breathing is only "controlled" ( Bernardi et al., 2000) as compared to directed in a specific direction. Note here the apparent contradiction with our own view that paying attention to the breath would result in lower respiration rate and possibly smaller inhalation/exhalation ratios: instructing to "control" vs. "focus on" seems to have opposing results on autonomic balance.

As we are reviewing breathing techniques that are practiced in ContActs, studies that look into autonomic functioning through ContActs employing these kinds of techniques should report increased vagal tone. Indeed, HRV increases in almost all forms of ContAct, consistent with the rVNS hypothesis. Different forms of meditation (e.g., body scan, FA, OM acem, zen) and mind-body exercises such as yoga, all show increases in vagal tone HRV in healthy participants ( Ditto et al., 2006; Phongsuphap et al., 2008; Wu and Lo, 2008; Tang et al., 2009; Markil et al., 2012; Melville et al., 2012; Nesvold et al., 2012; Telles et al., 2013). One exception is a study that involved the earlier mentioned "breath of fire" ( Peng et al., 2004) that showed a decrease in HF, LF and LF/HF ratio. This is not surprising and consistent with our biofeedback perspective, as breath of fire is strictly speaking controlled hyperventilation and would thus rather result in SNS activation and PNS inhibition. Though ContActs by great majority do not employ this particular rare technique, this nonetheless stresses the importance of mapping actual practiced techniques in every ContAct to their outcomes. From these abundant, though correlational, findings on respiration and vagal tone we conclude that a form of rVNS plays a role in ContAct efficacy. However, less clear is what the exact physiological mechanisms of stimulation might be.

Possible Mechanisms

The slowest of the indirect routes: biofeedback, where low respiration rate and small inhalation/exhalation ratio signal a resting state to the CNS is consistent with the James-Lange physiological feedback hypothesis of emotion and similar accounts ( Levenson, 1994; Critchley and Garfinkel, 2015). The theory, independently proposed by William James and Carl Lange, maintains that the identification and experience of an emotion follows from peripheral physiological responses (e.g., arousal), instead of the other way around. The kind of emotion experienced depends on the interpretation of the physiological state and the appraisal of the context in which it is triggered. So, the physiological stress response precedes the subjective emotional experience of fear or sadness. Following this argument, bottom-up changes to dysfunctional emotional states can be produced by changing the physiological state of the body; in other words: relaxing the body relaxes the mind.

In sum, there is evidence that particular breathing exercises (with low respiration rate, small inhalation/exhalation ratio) are capable of stimulating the vagal nerve (rVNS), though the exact mechanisms of stimulation are proposed, not proven (i.e., baroreflex). The next question is how prolonged increase in vagal tone results in the beneficial effects found on health and mental health. Vagal dominance is contingent on consistent physiological relaxation. It therefore produces (chronic) stress release, and thereby prevents or ameliorates stress-related pathology and etiology.

Relaxation vs. Stress: Health and Mental Health Outcomes

Although SNS and PNS can be simultaneously active in a particular domain, they mostly operate as opposing forces ( Berntson and Cacioppo, 1999; Freeman, 2006). SNS activity goes together with PNS inactivity and vice versa. Therefore, PNS hyperactivity (as indicated by HRV) also reflects SNS hypoactivity: vagal dominance. Plainly stated: relaxation means absence of stress. If ContActs work through relaxation by respiratory stimulation of the PNS, then stress should go down. This explains the observation that syndromes relieved after ContAct practice are often those associated with stress and SNS dominance.

The role of (chronic) stressors on the development of cardiovascular disease, through the cardiovascular response ( Obrist, 1981) of the SNS causing atherosclerosis and hypertension, is well documented ( Allen and Patterson, 1995; Rozanski et al., 1999; Thayer et al., 2010). That stress influences immune function is also well-known. Initially and acutely, stress suppresses immune function, but chronically it exacerbates immune response ( Sapolsky et al., 2000; Haroon et al., 2011; Ménard et al., 2017). Additionally, stress seems to worsen auto-immune disease ( Elenkov and Chrousos, 2002). Furthermore, there are indications that the two systems are related in their morbidity by SNS-PNS imbalance: recovery of both cardiovascular and immunological markers is impaired after stressors, when baseline vagal tone is low ( Weber et al., 2010). Also noteworthy is the existence of an inverse relationship between HRV and both inflammation and the risk of cardiovascular disease ( Haensel et al., 2008). Bringing these findings together, HRV seems suitable as a multi-index of health: of physiological stress ( Porges, 1995), as a measure of cardiovascular risk ( Thayer et al., 2010) and of immunomodulation ( Thayer and Sternberg, 2010).

A healthy autonomic balance is vagally dominated and comes about by stress relief produced by PNS activation and SNS deactivation. If this is the way the aforementioned pathologies are positively affected, then there should be a clear negative relationship between vagal tone and the risk factors and symptoms of these conditions. Indeed, HRV shows a negative correlation with cardiovascular disease in children and adults ( Tully et al., 2013; Oliveira et al., 2017) and even directly predicts hypertension ( Schroeder et al., 2003). It has an inverse relationship with inflammation ( Lampert et al., 2008; Kemp and Quintana, 2013), inflammation in depression ( Carney et al., 2007), depressive symptoms in children and adults ( Sgoifo et al., 2015; Koenig et al., 2016), perseverative cognition ( Ottaviani et al., 2016), bipolar disorder symptomology ( Faurholt-Jepsen et al., 2017), general anxiety and disorders ( Cohen and Benjamin, 2006; Tully et al., 2013; Chalmers et al., 2014) and has recently even shown a negative correlation with schizophrenia ( Clamor et al., 2016). Though schizophrenia is not considered a stress-related disorder, the role of HRV in schizophrenia is intriguing considering the interplay of dysfunctional emotional regulation and executive functions in its symptomology.

Stress has a negative association with executive or PFC function. Chronic stress has a degenerative effect on PFC structure and functioning ( Arnsten, 2009, 2015; McEwen and Morrison, 2013) and seems to adversely affect its plasticity ( McEwen et al., 2012). A study by Zhang et al. (2014), that builds on the correlational work of Nagai and others ( Nagai et al., 2004, see Critchley and Garfinkel, 2015, for a review) shows a causal involvement of ventromedial PFC in physiological arousal: when ventromedial PFC activity goes up, electrodermal activity (skin conductance level) goes down. In other words: prefrontal structures suppress stress. A conclusive review by the international behavioral neuroscience meeting ( Radley et al., 2015) stated the negative effects of stress on the plasticity of the limbic network (amygdala, hippocampus and PFC) and its pivotal role in the etiology of aforementioned (mental) health conditions.

In sum, (chronic) stress is a significant negative mediator in all of the domains that benefit from ContAct. It is here proposed that these beneficial effects occur by (chronic) stress relief as a result of vagal dominance by rVNS. In other words: breathing exercises produce stress relief ( Lee et al., 2003; Pramanik et al., 2009; Perciavalle et al., 2017). We have also already indicated that chronic and high levels of stress are negatively related to executive functions and PFC functioning. Next, we will show that there is also a positive relation between vagal tone, CAN areas and the executive functioning network, as predicted by the neurovisceral integration model, and between changes in CAN and ContAct practice as predicted by the rVNS model of ContAct.

CAN: Regulated Emotion and Enhanced Cognition

HRV, Cognitive Control and PFC

There indeed is an association between HRV and executive functions, as first shown by Thayer and Fischer (2009), especially in emotional control: HRV predicts inhibition of attention to emotional stimuli ( Park et al., 2012, 2013), it shows a positive relation to attentional control and negative relation to risk aversion in anxiety ( Ramírez et al., 2015), predicts attentional lapses ( Williams et al., 2016), and it is involved in cognitive inhibition, proactive cognitive control ( Capuana et al., 2012, 2014) and emotional inhibition of conditioned fear ( Wendt et al., 2015). A recent meta-analysis also supports a relationship between HRV and cognitive control: executive functioning, pooled across the subdivisions of Miyake et al. (2000), showed a positive average association with HRV level, though the authors note a strong publication bias ( Zahn et al., 2016). The effects can especially be observed in cognitively demanding settings. A brain imaging study shows that functional connectivity of the amygdala and medial PFC are associated with higher HRV in both younger and older people ( Sakaki et al., 2016).

Changes in CAN Regions Through ContAct

As we hypothesize that in ContAct rVNS is responsible for the emotional and cognitive enhancement by changes in CAN, studies looking at functional and structural changes in the brain in practitioners should show these changes along this whole network-in the limbic system and executive functioning network; in the levels of the updated neurovisceral integration model (see Smith et al., 2017). Studies on ContAct practice have shown this for the limbic part of CAN. For example, a decrease in volume and activity has been observed in the amygdala ( Hölzel et al., 2010; Tang et al., 2015) and in the hippocampus ( Luders et al., 2009, 2012c) in practitioners of different styles of meditation (both FA and OM). Insular cortex and posterior cingulate also increase in activity and volume in the same populations ( Lazar et al., 2005; Hölzel et al., 2011a, b; Kirk et al., 2011; Luders et al., 2012b; Tang et al., 2015). The practice of yoga shows the same pattern ( Froeliger et al., 2012; Desai et al., 2015), while a TCC study shows the most significant morphological changes in the insula and dorsolateral PFC ( Wei et al., 2013).

The ACC is a limbic structure, but is also part of executive functioning network and active in cognitive control, and is central in CAN. Notably its dorsal part has been implicated in autonomic control, as it modulates cardiovascular stress responses ( Critchley et al., 2003). Following the previous argument, ACC should also be implicated in imaging studies of ContAct efficacy, and indeed, functional and structural enhancement in ACC has been reported in meditation styles and in mind-body exercises ( Cahn and Polich, 2006; Tang et al., 2009, 2010, 2015; Hölzel et al., 2011b; Xue et al., 2011; Wei et al., 2013). The frontal end stations of CAN also show predicted structural changes: PFC gray matter density is increased by diverse meditation styles and mind-body exercises ( Lazar et al., 2005; Luders et al., 2009, 2012a; Lutz et al., 2015; Hölzel et al., 2011a; Froeliger et al., 2012; Tang et al., 2015; Wei et al., 2013; Yin et al., 2014; Desai et al., 2015). In sum, there is a large overlap between the brain regions changed by ContAct-amygdala, hippocampus, insula, ACC and multiple areas of the PFC-and those identified in CAN. Note, however, that these areas have been implicated in behavioral studies with very diverse tasks and contexts-not only in ContAct.

Default Mode and Executive Network Plasticity by VNS

In general, brain connectivity seems to increase by ContAct practice across multiple projections, commissures and associatedsociative networks, as shown by several diffusion tensor imaging studies ( Luders et al., 2011, 2012b). Meditation practice (and trait mindfulness) is associated with greater connectivity between the executive, DMN and salience networks specifically ( Brewer et al., 2011; Hasenkamp and Barsalou, 2012; Doll et al., 2015). Notably the DMN is implicated in neuroimaging studies among ContAct practitioners. DMN is active when external stimulation and work demand is low. Its main hubs are medial PFC, posterior cingulate cortex and parahippocampal region ( Raichle et al., 2001); the last of which is believed to operate as the hub between DMN and limbic areas ( Ward et al., 2014). The role of DMN in cognitive control can be seen as opposing that of the executive network; lapses of attentional control (i.e., mind wandering) are contingent on DMN activity over executive network activity ( Gratton et al., 2018), in this way DMN can be viewed as a "task-negative" network ( Fox et al., 2005). Studies on changes in connectivity by ContAct experience show deactivation of DMN hubs (i.e., posterior cingulate and medial PFC) and decreased functional connectivity between these hubs. At the same time the functional connectivity between the DMN and executive networks goes up ( Brewer et al., 2011; Hasenkamp and Barsalou, 2012). This mirrors what is consistently found in imaging studies that apply VNS to individuals with (treatment-resistant) depression.

Depression is associated with a disrupted DMN, particularly: hyperactivity and hyper-connectivity among DMN hubs, as well as hyper-connectivity between DMN and limbic system, and hypo-connectivity between DMN and executive network ( Drevets et al., 2008; Gong and He, 2015; Kaiser et al., 2015). Clinical trials employing chronic VNS in patients with depression show a normalization of this etiology, obtaining results very similar to ContAct practice. One study on patients with depression not responding to regular treatment showed increased metabolism in the DMN hub ventromedial PFC ( Pardo et al., 2008). While a similar study reported decreased activity (regional cerebral blood flow) in another DMN hub (posterior cingulate) and in the limbic system (insula), concurrently increasing activity in dorsolateral PFC of the executive network ( Kosel et al., 2011). Another imaging study (on epilepsy), reports a decrease in regional cerebral blood flow in the DMN hub parahippocampus, as well as in the hippocampus and the thalamus by chronic VNS ( Van Laere et al., 2002).

Concluding: it has clearly been shown that activity in afferent branches of VN can affect areas and networks in the CNS, both acutely (e.g., by tVNS) and chronically (e.g., by chronic VNS). This notably affects the DMN, which is a critical CAN level in the latest version of the neurovisceral integration model (see Smith et al., 2017 for details). Central changes as a result of ContAct practice within DMN and between DMN and executive network are practically identical to those observed by (t)VNS studies. This makes vagal involvement and thus the mechanism of rVNS highly likely in producing these neurobiological effects and the concomitant improvements in cognition and affect. Concretely stated: DMN deactivation and increased DMN-executive network connectivity is caused by rVNS and will lead to improvements in cognitive control (e.g., cognitive inhibition) and performance monitoring.

Discussion

We have shown that ContAct practices, though diverse, have a number of components in common that can explain their efficacy in individual physical health, mental health and cognition. Furthermore, one of these components: breathing techniques, is a prime candidate to explain the complete pattern of results, notably in the stress-related domain. We have further provided a neurophysiological model in which slow respiration and extended exhalation stimulate VN via two possible routes: rVNS. This results in PNS over SNS dominance, structural and functional changes in higher cortical areas through autonomic projections, and is thus responsible for aforementioned effects.

In these claims, one of the main arguments for the rVNS model of ContAct concerns the dovetailing between specific functions of VN with the pattern of effectivity shown by diverse ContActs; providing beneficial effects on cardiopulmonary fitness, immune function, psychological health, stress, anxiety and executive functions. The neurophysiological link between the two can be found in vagal tone: the existent relationship between the aforementioned functions and conditions with HRV and that of HRV with the VN. Evidently HRV is then an index of adaptability in a broad sense.

We realize that there might be more common factors involved in ContAct interventions than we have covered and categorized here. There also might be unique components to particular traditions, as well as emergent properties of specific combinations of components; almost all ContAct interventions are multi-modal. For example, many of the covered traditions are not practiced in isolation, but in group sessions. Social, and even physical, contact could be a factor in relieving stress and in alleviating depression. Though we do not discount the other factors covered and those possibly left out, we believe that respiration style and vagal functioning fit the evidence best, and following Occam's razor, it stands out as the most parsimonious of explanations. However, also rVNS might benefit from a specific combination. For instance, combining rVNS with affect training: exposure and reappraisal procedures could be strengthened by the concurrent body relaxation brought on by rVNS, the biofeedback would weaken the stress response and negative emotion brought up by an aversive or traumatic memory.

Following the observation on the multi-modality of ContAct, we maintain that many null-findings and conflicting results in the literature could be ascribed to the presence or absence of particular effective components. For example, a yoga class only focusing on stretching and shifting positions might not have any executive functions benefits other than those stemming from some form of relaxation, but does show changes associated with mild exercise. Studies performing systematic analyses that compare functional ContAct elements, based on concrete predictions, are therefore sorely needed. Reported findings that show controlled breathing increasing SNS activity further underline the importance of making clear what kind of techniques are employed. This includes reporting on the exact instructions given and controlling for compliance to these instructions. Our predictions are only valid as far as interventions result in slow, deep (diaphragmatic) breathing-not in other breathing styles, such as fast and deep breathing during physical exercise. Thus, the described beneficial effects on health and cognition are predicted to occur more in ContActs with breathing exercises stressing relatively short inhale (SNS controlled) and long exhale (PNS controlled), than in ContActs that do not emphasize this distinction.

Some ContAct practitioners might proclaim that their particular tradition (notably FA) does not involve any breathing exercises. That the exercises only instruct to pay attention to the breath, and not to modulate respiration in any way; that instructions to change anything in breathing patterns are absent. They might also state that the breath is only one of many foci. For example: it could be a visual focus, such as a flickering candle flame or verbal, as in a mantra. But the fact is, that across these diverse FA traditions it usually is not another kind of focus, it usually is the breath, and we maintain that this is not arbitrary. As previously stated, we maintain that it is unlikely that focusing on the breath does not affect respiratory patterns. In our view, directed conscious awareness to breathing will slow respiration in expert and layman alike, through direct and indirect experience with different breathing exercises and the implicit or explicit idea, an ideomotor representation if you will, what it should be like to meditate: meditating involves relaxed breathing. Furthermore, the rhythm of auditory instructions is in a slower pace than normal breathing, thereby slowing respiration as well. Of course, these are assumptions that should be tested in further experiments. But, if attention does slow respiration, this makes all these traditions fall under the explanatory umbrella of the rVNS model of ContAct.

So far, the picture painted from rVNS has been optimistic. However, there might be circumstances and doses where no beneficial effects can be expected. For example: in chronically stressed individuals vagal activation might have such a high threshold that rVNS will have no noticeable effect; they might prove resistant to the intervention. rVNS might even have adverse effects, such as overstimulation. In a condition known as vasovagal syncope, vagal efferents reduce heart rate to such a degree that blood pressure drops to dangerous levels, resulting in fainting and symptoms of chronic fatigue. As indicated by VNS studies showing bronchoconstriction, stimulation might be dangerous for pulmonary pathology, such as chronic asthma ( Hajnšek et al., 2010). However, studies varying VNS voltage suggest that strength of stimulation could make the difference between beneficial or detrimental ( Hoffmann et al., 2012). Respiratory VNS might be as beneficial and healthy as the individual baselines (e.g., autonomic balance) allow. By extension, these dangers could be present for ContAct practices as well. But as far as we know, there are no studies on adverse effects produced by ContActs. This does not deny their existence as the absence could be a result of publication bias.

In light of the necessity to report the specific instructions and exercises in every intervention study, mention has to be made of mindfulness meditation. When we and many other authors report on mindfulness meditation, this usually refers to two clinical programs: mindfulness-based stress reduction and mindfulness-based cognitive therapy. Both of these are multi-modal interventions, in which not only mindfulness meditation and other meditation techniques play a role, but also physical exercises (some form of yoga), mental strategies, and in mindfulness-based cognitive therapy: cognitive-behavioral therapy. Most studies that report on the effects of mindfulness or mindfulness meditation, that use these programs as interventions, should therefore strictly speaking not be taken as "pure" mindfulness meditation; subsequently, caution is advised in interpreting result.

Though we are not able to definitively prove a causal link between breathing, VNS and improvements in body and mind, we believe we have provided ample evidence suggesting the existence of this link, largely by providing overlapping patterns of specific phenomena. Empirical studies need to put our hypotheses to the test. Furthermore, other concrete neurobiological mechanisms for the systems described in this work need to be proposed and charted by experimental studies, as prescribed for the field by Thayer et al. (2011). Studies on different respiration styles, using psychophysiological measures for PNS and SNS activity and tasks assessing executive functions acutely and longitudinally could provide concrete tests of our hypotheses. Imaging studies mapping structural and functional changes in the CAN following rVNS are critical for our hypotheses on cognitive functioning, especially: changes in DMN and executive network mirroring VNS results are expected. Other indirect tests include experiments comparing ContAct interventions with (t)VNS manipulations. As an established phenomenon, studies of rVNS dose-response relationships, with personal baseline levels, could follow. What is the "vagus code" of rVNS ( Kwan et al., 2016)? What are observed differences caused by specific modes of stimulation? For instance, electrical VNS and behavioral rVNS differ also in laterality: unilateral vs. bilateral stimulation, which might produce different effects (and strength of stimulation).

Lastly, as for the reasons why breathing techniques have gone pretty much unnoticed as a mechanism of ContAct efficacy, while being so prevalent and well-known, we propose that it perhaps has to do with this prevalence: it is such an unremarkable fact, so plainly observable and a starting point of practice. This could be coupled with a tendency to focus on "higher" levels of consciousness among practitioners, and on higher level processes and structures in cognitive neuroscientific research. Relaxation might also be assumed and uninteresting, breathing exercises are automatically factored in, something for novices, hardly remembered by the expert. We hope that through this work future research on ContActs will recognize and study breathing techniques as an effective component, and that neuroscience will focus on rVNS respiratory patterns as potential cognitive and (mental) health enhancers.

Author Contributions

RG conceived the presented idea, developed the model, posited possible mechanisms and wrote the main drafts. GB supervised the project, and edited and rewrote manuscript drafts. All authors contributed to the final version of themanuscript.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

We want to thank Marieke van Vugt and Henk van Steenbergen for commenting on an earlier version of this work.

Abbreviations

CAN, Central Autonomic Network; ContAct, Contemplative Activity, such as meditation, mindfulness and yoga.; FA, Focused Attention meditation; OM, Open Monitoring meditation; PNS, Parasympathetic Nervous System; rVNS, respiratory Vagal Nerve Stimulation; SNS, Sympathetic Nervous System; TCC, Tai Chi Chuan; VN, Vagus Nerve.

References

Andrews, P. L. R., and Lawes, I. N. C. (1992). "A protective role for vagal afferents: an hypothesis," in Neuroanatomy and Physiology of Abdominal Vagal Afferents, eds S. Ritter, R. C. Ritter, and C. D. Barnes (Boca Raton: CRC Press), 280-303.

Levenson, R. W. (1994). Human emotion: a functional view. The Nature of Emotion: Fundamental Questions, eds P. Ekman and R. Davidson (New York, NY: Oxford University Press), 123-126.

Pramanik, T., Sharma, H. O., Mishra, S., Mishra, A., Prajapati, R., and Singh, S. (2009). Immediate effect of slow pace Bhastrika Pranayama on blood pressure and heart rate. J. Altern. Complement. Med. 15, 293-295. doi: 10.1089/acm.2008.0440

Wayne, P. M., and Kaptchuk, T. J. (2008). Challenges inherent to Tai Chi research: part I- Tai Chi as a complex multicomponent intervention. J. Altern. Complement. Med. 14, 95-102. doi: 10.1089/acm.2007.7170A

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Breath of Life: The Respiratory Vagal Stimulation Model of Contemplative Activity

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Contemplative practices, such as meditation and yoga, are increasingly popular among the general public and as topics of research. Beneficial effects associated with these practices have been found on physical health, mental health and cognitive performance. However, studies and theories that clarify the underlying mechanisms are lacking or scarce.

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5 Strategies to Challenge Negative Thoughts

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5 Strategies to Challenge Negative Thoughts

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Stop for a moment and think about this: What do you actually think about yourself?

There's the shiny, confident exterior you show the world, but at the end of the day, when you're alone with your thoughts, what do they say to you?

Executive coach and Stanford MBA Shirzad Chamine asked more than 100 CEOs at a seminar this question, which they answered anonymously on flashcards. During a recent talk at Stanford Engineering's eCorner, he read some of the answers aloud.

"I'm rarely at peace with myself."

"I'm self-destructive and I don't know why."

"I don't love myself very much."

"I'm feeling very sad and lonely, and the anti-depressants I'm on don't seem to be helping."

"I battle with constantly ranking and judging everyone around me, in all settings, all the time."

Chamine has spent the majority of his career trying to understand the drivers behind our most critical thoughts and whether it's possible to escape them. Over time, he developed an analogy of how the human mind works that he uses to help others break out of self-destructive mental loops and become happier and more productive at work and in life.

At his recent talk, he shared five strategies to help people who want to challenge their negative thoughts.

Strategy #1: Learn How to Meditate in Stressful Situations

Everyone listens to a private, running inner monologue of positive and negative thoughts. Chamine says if you pay attention to your inner monologue, you can begin to understand what triggers your negative thoughts and consciously put yourself on a more positive mental track.

Meditation is a good first step; it allows you to focus on that voice and shift your inner perspective. The majority of people who meditate do so early in the morning, when things are quiet and they're preparing themselves for the day ahead. But one long commute, four harried meetings, and six urgent deliverables later, those calming, positive thoughts are long gone for most people.

"You need to learn how to activate that brain in the middle of war, in the middle of challenges, in the middle of crises," Chamine says. "Most meditators don't learn how to activate that brain when they really need it."

He shared a practical tip to spark mindfulness and calm in any situation: Slowly rub your index finger against your thumb, so that you can feel the individual ridges of your fingerprint. Try it for 10 seconds at a time. Focusing on that sensation can help ground you and break a negative mental cycle.

Strategy #2: Listen to Your Mental Criticism, but Don't Dwell on It

In your worst moments in life, you likely heard your inner voice turn dark, preying on your insecurities and anxieties, causing feelings of anger, disappointment, shame, guilt, and regret. Those reactions are valuable, up to a point, in that they provide feedback about a mistake to avoid in the future.

But left unchecked, negative inner monologues can stretch out, taking days, weeks, or even longer to work out. It's important to recognize constructive internal feedback at the moment it happens, but not allow those thoughts to run rampant in your mind.

"Is it good to feel pain? Of course!" Chamine says. If you put your hand on a hot stove and you don't feel pain, you'll burn your hand to the bone, he says. Feeling pain is a good warning. "The question is, how long would it be good for you to feel the pain before you remove your hand from the hot stove? And the answer, hopefully, is a split-second. Just long enough to know that there is a problem here. It's the same with negative emotions."

Registering negative emotions as feedback, and then consciously returning to a more positive frame of mind is crucial for achieving your full potential.

"Your highest performance comes from the brain that is calm, centered, focused, able to see possibilities and be creative," Chamine says. That's not possible when you're stuck in a negative feedback loop.

Strategy #3: Recognize All the Forms Your Mental Criticism Comes in

In the course of his work, Chamine identified a handful of types of negative voices that are capable of sabotaging your happiness, productivity, and positive feelings of self-worth - a group he calls Saboteurs. The dominant Saboteur everyone carries with them is the Judge - the voice inside you that judges your own actions and the actions of everyone else.

Armed with the power of perfect hindsight, your inner Judge berates you for mistakes you should have seen coming and criticizes you for falling short of your goals. Some people allow their inner Judge to become such an integral part of their life that it becomes their dominant personality trait.

Hiding behind the Judge is a host of smaller Saboteurs - the Controller, the Restless, the Stickler, the Pleaser, the Avoider, the Victim, the Hyper-Vigilant, the Hyper-Achiever, the Hyper-Rational.

Chamine examines each in detail in his bestselling book, Positive Intelligence. He says an easy way to understand which Saboteurs rule your life is to complete the following sentence: "To survive and succeed, I should _____." Your answer can provide insight into what actually motivates you.

Chamine says some of the world's most outwardly successful people are ruled by their various Saboteurs. Using negative emotions as fuel to push them, they'll ultimately fall short of their true potential, he says.

"So long as the Saboteurs are pushing you to your level of success, you will never be happy, because every step of the way is littered with negativity," he says. "Your path to highest performance is not through the Saboteurs."

Strategy #4: Listen to Your Inner Sage

The counterbalance to each person's cast of Saboteurs is a calm, positive, optimistic voice that Chamine calls the Sage. Rather than picking apart every mistake you make and every shortcoming you find in the people around you, your inner Sage instead tries to see the positive in every negative.

"One of the number one tools that high performers use, every time life throws [challenges] at them, one of the ways they quickly recover to a positive place ... is to ask the question, 'How do I turn this into a gift and opportunity?'"

Looking for the gift, no matter how small, in each negative experience helps reframe the thoughts associated with the experience.

In his work, Chamine describes five attributes, or powers, of each person's inner Sage: the power to empathize, explore, innovate, navigate, and activate.

Together, these powers work to create a more positive internal worldview, and allow you to focus on what's in front of you, rather than worrying about what's next.

Strategy #5: Take It One Step at a Time in the Right Direction

Your path is fundamentally yours to chart, Chamine says. There's no map to self-actualization; it's a process that's done one day at a time, and more granularly, one thought at a time.

In his lecture, he described charting your path like standing at the edge of a dark forest, with a lighthouse in the distance. Getting to the lighthouse is a goal taken one step at a time.

"At any given step, take the step that has more light in it," he says. "Only after you take that step, the step after that will reveal itself."

After each step, he says, you will get "closer and closer to the lighthouse, to your true self, to your final self-actualization."

But nobody ever gets to the lighthouse, Chamine says. The value lies in the journey to improve how you think about yourself and your world.

"You begin to run into people around you that are on a similar path that can help you with that path, and you begin to discover amazing things because you're paying attention to every step," Chamine says. "Self-actualization ... and following your calling is not about one destination that one day you're going get to. It's about every step."

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Shirzad Chamine: Five Strategies to Challenge Negative Thoughts

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Stop for a moment and think about this: What do you actually think about yourself? There's the shiny, confident exterior you show the world, but at the end of the day, when you're alone with your thoughts, what do they say to you?

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Sources of Insight: Build Your Positive Intelligence with PQ Reps

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Sources of Insight: Build Your Positive Intelligence with PQ Reps

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How To Build Your Positive Intelligence with PQ Reps

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"The positive thinker sees the invisible, feels the intangible, and achieves the impossible." - Unknown Positive Intelligence, or "PQ", is potentially the best predictor of how happy you are and how well you perform relative to your potential. Positive Intelligence is effectively the backbone of your mental fitness.

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How to end stress, unhappiness and anxiety to live in a beautiful state | Preetha ji | TEDxKC

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Vagus Nerve Massage For Stress And Anxiety Relief