In Latin, the word “vagus” means wandering, a fitting description for this meandering nerve that stretches from the brain stem down to the colon, connecting to the middle ear, vocal cords, heart, lungs, and intestines along the way. The longest and most complicated of the body’s 12 cranial nerves—each connects the brain to other parts of the body—the vagus nerve plays many roles, affecting our emotional states, heart rate, inflammation levels, blood pressure, and digestion. It interacts with our autonomic nervous system (or ANS—a part of the nervous system that has three branches responsible for unconscious processes, such as digestion and breathing). In particular, it’s an advocate for the parasympathetic nervous system—the branch of the ANS that stimulates the body to “rest and digest.” The vagus nerve thus has a profound impact on our sense of safety and connection.
What’s the Message?
“The vagus nerve is like the highway of information for the parasympathetic nervous system,” says Dr. Brendan Kelley, professor and clinical vice-chair in the Department of Neurology at UT Southwestern Medical Center. The vagus nerve carries signals—neurotransmitters—between the emotional center of the brain and organs like the heart, lungs, and stomach. These signals instruct specific organs to respond and function accord- ing to three states: safe and social, fight and flight, or freeze and immobilize. As deep breaths slow your heart rate, for example, your vagus nerve recognizes the cues of safety and sends that information to parts of the body so they can turn off their defenses, such as those that arise from a sense of anxiety or threat. “The brain is reading and regulating your body through this nerve,” says Dr. Stephen Porges, a Distinguished University Scientist at Indiana University and creator of the polyvagal theory, an understanding of the nervous system and how the tone (that is, the activity) of the vagus nerve directly affects our well-being. “The body won’t function optimally,” he adds, “unless it picks up cues of safety.” Working with mind–body tools, especially the breath, helps to moderate the communication between the sympathetic (another branch of the ANS that stimulates the fight-or-flight response) and parasympathetic nervous systems. “The breath can be used as a gas pedal and as our brakes,” says Arielle Schwartz, PhD, a clinical psychologist and certified yoga instructor. “If I’m feeling shut down and need more alertness, I can bring in some breath of fire; or if I’m feeling anxious and panicky and I want to tap the brakes, I’ll emphasize long, slow exhales and deep belly breathing.”
Safe and Social
In social interactions, we tend to focus on behavior—both ours and the person with whom we’re interacting. But Porges’ theory suggests that sociability is not only about voluntary behavior, but rather is rooted in neurobiology. The vagus nerve is involved in how we respond to people around us, notes Kelley, whether it’s a loving, caring interaction, or one involving fear and anxiety. How the vagus nerve will respond—whether it activates or deactivates—comes down to what the particular situation calls for. Porges offers the example of a mother’s role to calm a child with a facial expression, a touch, a soothing voice—which activates the vagus nerve—and how the resulting state of calm allows the child’s body to regulate, and if necessary, to heal. “When you get rid of the threat reaction, you become calm and more present,” says Porges. “The body can then solve problems on a neurophysiological level, optimizing how the visceral organs function.”Sometimes, your vagus nerve needs to deactivate to allow you to access your threat (fight-or-flight) response. For example, hearing sounds such as a dog barking aggressively or a loud clap of thunder will cue the vagus nerve to deactivate, so you can react accordingly and protect yourself. “If we get anxious, we can’t breathe correctly and we turn off the mechanism through which the vagus nerve will calm us down,” says Porges. This deactivating response can also arise m through nonthreatening and even enjoyable situations, Kelley explains. Picture players in a soccer game: When the body needs blood to run fast, it can’t also direct resources to a task like digesting our last meal. According to Kelley, “The sympathetic nervous system really narrows our attention to focus on the matter at hand”—a side benefit of the fight-or-flight response.
A Signal for Compassion
In social settings, the vagus nerve encourages what Porges calls the “compassionate witness,” a physiological state where a person is not throwing out cues of anger, threat, or hurt, but is there as a peaceful and supportive observer. “The co-regulation helps the nervous system of the person who’s been hurt to feel safe enough without being defensive, to feel calm and validated,” says Porges. While further research is needed to illuminate how specific emotions relate to vagal tone, a 2015 paper published in The Journal of Personality and Social Psychology found that feeling compassion, “when encountering the suffering of others, leads to markedly greater vagal activity compared with neutral or other emotional states,” according to the researchers. Four studies compared undergraduate participants’ RSA (respiratory sinus arrhythmia, a common measure of cardiac vagal function) during different positive emotional states. Results showed the participants’ RSA was greater while they were feeling compassionate than while they were experiencing either pride or inspiration.
Can You “Improve” Vagal Tone?
While the tone of the vagus nerve directly affects our well-being—specifically, our capacity to self-regulate and to connect with others—Kelley adds an important nuance: Although we can measure vagal tone, it’s not a general indicator of how well a person manages stress. When we’re relaxing, our vagal tone will naturally be higher; when we’re active or under pressure, the nerve is not needed and effectively “shuts down.” “Our ability to handle stress is tied up in our brain and emotional world. Vagal tone is just a reflection of that point in time,” Kelley summarizes.
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