THE ANCIENT NERVE
Porges is a rare bird among scientists, a guy who has spawned his very own theory of human behavior, an idea that has acolytes and practitioners and real-world, on-the-ground applications. For instance, at the Center for Discovery in New York, we met a young, bright guy from MIT, Matthew Goodwin, who had used Porges’s ideas to incorporate the same sort of telemetry that lurks in the guts of an iPhone to track and predict disruptive outbreaks in autistic people. This is the sort of application that started Porges thinking about all of this decades ago—the idea of measurable, readable physical manifestations of our state of mind, a literal pulse of our psychological well-being.
The vagus nerve is the only one that attaches to the most primitive, lower part of our brain, and from there it winds the unique and circuitous course that earns it its name. Unlike most other nerves in the body, it wanders, not straight from eyeball to brain like the optic nerve but downward along the neck and then branching and twisting through the core of our body, our guts, our gonads, our viscera, and if you hear in this the word “visceral” you are hearing right. But then, oddly, parts of it twist back up through the throat to take in larynx, ears, facial muscles. Why this odd assortment of disparate organs and functions? What does our heart—just a pump, really—have to do with the crinkle in the corners of our eyes?
This tortuous path, starting as it does in the most primitive part of our brain, is first an evolutionary trail, and it clearly marks the vagus as ancient. It makes its straight march to the chest and heartbeat but also back upward to innervate structures that had their origins in the gills of our very distant ancestors. It is an integral part of a network known as the autonomic nervous system, which regulates automatic responses in our organs—but not only automatic responses. Among the system’s key tasks is regulation of our body’s response to threat, terror, and lions, the center of control for fight, flight, or freeze.
When presented with a threat, each of these strategies requires regulation throughout the territory covered by the vagus nerve and the rest of the autonomic nervous system. For instance, heart rate and respiration increase, both effects that supply extra energy for fight or flight. The digestive system shuts down to save energy. Same with the gonads. Same with immune response. Facial muscles contract and contort to the fierce presentation of rage. The larynx tightens to pitch urgent vocalizations. This is your body at DEFCON 1. And then the threat passes, and the vagus nerve reverses all of this. The whole cycle, arousal and relaxation, is an oscillation that is adaptive and serves as the successful response to danger.
In all of this, the shutdown sometimes gets taken for granted, but it is not a given. The terror response doesn’t just stop on its own; it requires a whole separate set of signals to shut it down. Over time, people who are repeatedly abused or terrorized, especially as children, lose the ability to return to normal, almost as if a switch got stuck. They literally live in terror. Further, tracing the course of the autonomic nervous system shows quickly why so many issues deemed psychological play out in the body: digestive issues, impotence, poor immune response, high blood pressure, elevated heart rate, tense faces.
A curiosity about the physical manifestations of a psychological state is what brought Porges to the vagus nerve in the first place. What kept him there was the realization that the vagus nerve runs both ways. It is mostly a control nerve, signaling organs to relax, but it also sends information back up to the brain on the state of the organs.
Begin, though, by understanding that social engagement, the ability to deal with another of our species on the basis of trust and understanding, is, in terms of all animals, truly bizarre behavior. Almost no other species can do it as well as we do, and those that can, like dogs, tend to hang around with us. Porges says the reason this is so in evolutionary terms is that very few species have the ability to apply the vagal brake. The ability to calmly speak with one’s spouse as to the whereabouts of the espresso tamper means asking the autonomic nervous system to perform two contradictory goals at the same time—and the key to that, says Porges, is the vagal brake. The vagus nerve links up all the tools we need to respond to an existential threat, and so the vagal brake is a signal sent through the system for everything to stand down and engage—at ease.
And it turns out there is a simple measure of this. It can be read in the tension or lack of tension in facial muscles, heard in voice timbre and edge, and counted in rate of respiration. But at the heart of the matter is the heart itself and a subtle little signal called the respiratory sinus arrhythmia. When the vagal brake is applied, it calms the heart as it does everything else, and the unequal pressures of breathing (the increase with inhalation and decrease with exhalation) actually syncopate the heartbeat with a little asymmetry in rhythm, a slight difference between contraction and expansion. This is a respiratory arrhythmia and the syncopation can be read on a graph, plain as day. Further, says Porges, there is such a thing as vagal tone, completely analogous to muscle tone—and the tone shows how clear and distinct a given individual’s ability to apply the brake is. That tone can be read in the amplitude of the arrhythmia. People who are comfortable engaging other people have strong vagal tone.
For openers, this realization revitalizes a whole collection of metaphors in our language and most others by suggesting that they are more than metaphors. A strict rationalist’s reading of statements like “I know it in my heart” or “My heart is not in this” sees them as a cover for mushy thinking. In strict, reductionist, mechanistic thinking, the heart is just a pump, not so different from the circulating pump in the boiler in the basement. (Likewise, science has begun talking about a “second brain” in your body: the enteric nervous system. We have long known that the digestive system has a robust set of nerves of its own, but research is finding out that this system does far more than regulate digestion. It is a full complement of neurotransmitters and, in fact, seems to play a key role in regulating your sense of well-being, both physical and mental. It plays a role in your decision process, hence “second brain.” Now metaphors like “gut instinct” get some real-world traction.)
Yet it now seems as if there was an instinctive understanding in the evolution of our language that recognized what we can now measure in graphs and blips and charts: that the heart and gut are deeply engaged in our emotional lives. But this might seem a bit much on the evidence we’ve delivered so far. It’s cool that the heartbeat gives us a measure, but so what? It’s only a slightly more sophisticated measure than, say, rate of respiration, galvanic skin response, or a twitch in our facial muscles that any dog can read.
To which Porges replies, no, no. The vagal brake can be driven by breath, a clear connection readable as blips on a chart. You are in control of your breath, to some degree. Thus, this is not simply a point for measuring or sensing arousal; it is a point for controlling arousal and, downstream, the health problems that stem from lack of control.
We have long had intriguing clues as to how our body might participate in psychological health. For instance, it is a no-brainer that if you feel better, you are more likely to smile. But people studying depression figured out long ago that if you force yourself to smile, the specific spots in the brain that register depression suddenly say your depression is better. Nothing else changed in your life, so why should this be? Through the years, neuroscience has produced a refinement of this intriguing little bit of information. It turns out that a halfway, forced smile won’t do the trick because it won’t light up the neurons of increased happiness in your brain. But if that forced smile goes so far as to engage the little muscles in the corners of your eyes—that is, if you do what socially adept people understand instinctively—these neurons do indeed light up. And the muscles at the corners of your eyes are within the reach of the vagus nerve.
Yet where this idea really hits home is with the breath, the one response over which we have control and which, in turn, exerts control through the alarm system that is the autonomic nervous sy
stem. Porges says he realized a long time ago—because he is a musician, specifically a horn player—that the act of controlling the breath to control the rhythm of music and at the same time engaging the brain to execute the mechanics of music works like a mental therapy. To his mind, it has all the elements of pranayama yoga, a form of yoga that stresses breath control.
Breath control is common in most of yoga but also in meditation, and even in modern-day “evidence-based practices” like cognitive behavioral therapy. Relax. Take a deep breath. This act of controlling the breath has a parallel brain response of calming our instincts for fear and danger. It’s easy enough to see this in deliberate practices like yoga, but the same idea applies in many more time-honored practices: choral singing, Gregorian chants, even social music like bluegrass or blues derived from the chants and work songs that African slaves developed to help them tolerate oppression.
There is, in fact, a musical thread throughout this idea. There is a bias in the system to detect what Porges calls prosody, the rhythm and lilt we associate with music, singing, poetry, and chants. It is the form that becomes immediately apparent in our voices when we talk to animals or babies and is the language of our foundational relationships with our mothers. Prosody is the form of speech the San people used to engage lions.
All of this begins to explain a curious finding among the bones and ruins of our ancestors, such as flutes carved from the leg bones of cranes. Recall that music or evidence of music appeared fifty thousand years ago in that sudden flourish of evidence of cultural evolution that defined humans as humans—and ever since, music has loomed as a cultural universal. All known cultures and peoples make music. Yet all of this also suggests that we lose something when the crane’s leg bone gets replaced by an iPod. We lose the benefits of sitting in a circle of fellow humans and driving the breath and beat that drives the music.
The psychiatrist and neuroscientist Iain McGilchrist argues that music predated language in human development, simply because it was more important, more necessary, and already developed by evolution in other animals like birds and whales. Language merely allowed communication. Music and components of music like lilt and prosody facilitated engagement, even with other animals, even with predators. It engaged the breath in its making.
CONNECTIONS TO PHYSICAL WELL-BEING
The vagus linkage suggests that these sorts of activities might well extend beyond emotional well-being simply because so many of the physical maladies of modern times play out in the territory of the vagus nerve and the enteric nervous system. Your yoga practice or your choral group may well have some leverage on your irritable bowel syndrome or the persistent pain in your neck for no apparent reason, because both of these are wired to the signal path of breath.
But what of exercise—pumping lungs and heart in exertion? Porges says it depends. Done wrong, exercise can drive the emotional response in the wrong direction because it relies on arousal—the physical arousal that is the opposite of relaxation. But this is not the contradiction it seems to be. In much of the animal world, the choice is either fully aroused or fully shut down, but the sophisticated autonomic nervous system of humans allows us to accomplish both at once. The most profound statement of our ability to deal with contradiction is sexual congress, the state that demands arousal in the most basic and heart-thumping sense, and at the same time requires maximal emotional openness and engagement—that is, trust. The standout ability of a well-adjusted human is to handle both arousal and engagement at once in this and all other forms of social intercourse.
Which turns out, in Porges’s view, to be terribly relevant to that workout of yours at the gym. Simply plunking yourself on a treadmill or stationary bicycle, armoring with earbuds to shut out auditory signals from the real world, and then watching cable news loop the litany of the day’s lurid images—he argues that this speaks straight to the reptilian reaches of the nerves. Remember, you are running, as in “flee.” Running is a setup for working the grooves of panic. The alternative, though, is group activity, group play and exercise, the very sort of activity that humans seem to have preferred through the ages. Done right, this does indeed involve the arousal of the flee response, but also the social engagement of teammates and competitors and the rich sensory messages from nature and the outdoors. Now both arousal and engagement are activated, meaning your heart, body, and mind are fully involved in the most elaborate of social exercises. All of this puts a new layer of foundation beneath developments like Eva Selhub’s and Matt O’Toole’s enthusiasm for the CrossFit gym. Even more deeply, it helps us see further significance in ancient activities such as persistence hunting, always done in groups with sublime levels of engagement and communication among members. Persistence hunting also required an almost instinctive level of understanding and predicting the movements of the animal being tracked, a skill that observers recorded as based in empathy.
TRAUMA
One of the best windows into the relevance of all of this frames a view most of us would prefer to avoid, filled as it is with nightmarish visions. Because while the vagus nerve is central to our trust and social connection, it is also central to terror, and too many of us live at the reptilian level of this response.
The guy generally credited with having done more thinking about this than anyone else is trauma researcher Bessel van der Kolk. Porges talked much about trauma during our interview and at least part of the credit for that, he acknowledges, goes to his association with van der Kolk.
Van der Kolk grew up in the Netherlands, but as a young man he came to Boston and trained as a psychiatrist and then became involved in treating veterans of the Vietnam War who were plagued with psychological difficulties as a result of their experiences. At that time, there was a vague notion of the source of those troubles, labeled in earlier wars as “shell shock” or “battle fatigue.” But as a result of work during the Vietnam era, psychiatry gave this problem a formal diagnosis of post-traumatic stress disorder, or PTSD, a diagnosis that van der Kolk helped formulate.
Shortly thereafter, though, he became interested in the problem as it plagued children, and he has founded a national network sanctioned by Congress to research what he calls “developmental trauma.” The difference between the problem in children and in adults is critical and serves as the main finding of the whole area of research. Child abuse occurs while a helpless brain is still physically forming, and so it locks in patterns of neural response largely through the mechanisms of fight, flight, or freeze. This means that the effects of childhood traumatic events linger, in fact dominate, well into adulthood, and in some surprising ways that speaks directly to what ails us.
The pivot point in this thinking was a landmark study taken on by the Centers for Disease Control and Prevention. It looked at seventeen thousand middle-class employed adults in California and assessed their history of childhood abuse against the primary causes of premature death in the United Sates, like heart disease, diabetes, stroke, and liver disease—our nation’s most expensive public health problems. The results are head-turning. The researchers found, first, that there is a surprising amount of abuse in most people’s lives—physical, mental, and sexual abuse as well as the experience of growing up with violent or alcoholic parents. More important, though, the researchers found that not only did abuse serve to predict poor health later in life, but the amount of abuse was directly related to the severity of the later health problems; it was, in the language of epidemiology, “dose-dependent.”
Some of this can be explained by the usual routes. People abused as children tended to self-medicate as adults with alcohol, drugs, and cigarettes, and those behaviors in turn sponsored some of the later health problems. But the researchers performed statistical techniques to account for this and still showed a straightforward physical response to child abuse. This may seem a strange connection, unless one realizes that the diseases in question affect organs like the heart and lungs and processes like digestion and immune response, all of which falls
into the territory of the vagus nerve.
“Trauma lives in the body,” van der Kolk says often, an aphorism that tracks the vagus nerve but also the path of his own career. He has been known to state bluntly that despite his training and lifetime of experience in psychiatry, what he has learned through trauma has caused him to stop practicing psychotherapy. He is openly and frankly dismissive of talk therapy, labeling it “yakking.”
And so one cold, gray afternoon in Boston, we found him holed up in a modest little ground-floor office in a brick town house, where we’d come to ask him what works—what makes people better.
“Trauma is about immobilization,” he says. “What works is people moving together in time, rhythmically.” Through the decades of his dealing with this problem, he’s gotten results by making people move.
People who have been abused, especially as children, are often simply practicing the normal and adaptive response of freezing. That’s the tool that evolution gave us. The trauma response is not a mental disease or failure of the genes and neurons; rather, it is a normal response to an abnormal situation. And at the same time, we are evolved and adapted to return to normal, to begin motion again, once the danger passes. The problem, especially with children but also with warriors who suffer PTSD, is that the danger and terror happen again and again and again; they become a way of life, and over time the biochemical and neurological systems for returning to normal, for modulating, for shutting down the alarm, just lock in place instead. And the body seizes up in the bargain. Maybe not in complete paralysis, but parts of the body do freeze, terrified to move.
“Immobilization without fear, which is really what society is all about, as opposed to immobilization with fear, which is what trauma is about,” was the way Porges expressed this to us.
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