What is the Vagus Nerve?
The vagus nerve is a major conduit for bi-directional communication between the brain and body, relaying sensory signals from internal organs and transmitting motor commands from the brain. As a key regulator of homeostasis, it supports critical autonomic functions including heart rate, digestion, immune response, and inflammation modulation [1, 2].
What does the Vagus Nerve do?
MOOD
As a key component of the parasympathetic nervous system, the vagus modulates your body’s stress response. As cranial nerve X, it originates in the brainstem and influences the limbic system, which is responsible for regulating emotions and mood [1].
FACIAL & VOICE EXPRESSIONS
Through its coordination with cranial nerve VII (facial nerve), the vagus supports expressive communication.
It directly modulates vocal tone via innervation of the laryngeal muscles and indirectly contributes to prosodic and affective signaling.
BREATHING
Although the vagus nerve plays an essential role in autonomic regulation of respiration, it does not directly control the diaphragm. The phrenic nerve, originating from the cervical spinal cord (C3–C5), is the primary motor supply to the diaphragm. However, the vagus nerve modulates respiratory patterns by coordinating brainstem circuits, including the nucleus ambiguus and the pre-Bötzinger complex, which influence parasympathetic output to thoracic organs. This regulation affects respiratory sinus arrhythmia (RSA)—a measurable rhythm reflecting vagal modulation of heart rate during breathing. Through these integrative mechanisms, vagal activity contributes to the coordination between cardiac and respiratory rhythms, supporting efficient gas exchange and autonomic flexibility.
HEART RATE & BLOOD PRESSURE
The vagus nerve plays a key role in regulating heart rate by releasing specific neurotransmitters that slow down the heart rate, promoting a state of relaxation [2]. The right vagus predominantly innervates the sinoatrial node, modulating heart rate, while the left vagus more strongly influences atrioventricular conduction and may, in specific contexts, modulate cardiac contractility.
IMMUNE FUNCTIONS & THE INFLAMMATORY REFLEX
The vagus nerve plays a key role in modulating immune function through what is known as the inflammatory reflex—a neuroimmune feedback loop. Afferent vagal fibers detect peripheral inflammation and transmit this information to the nucleus tractus solitarius (NTS) in the brainstem. Following central integration, efferent vagal signals—especially via the cholinergic anti-inflammatory pathway—inhibit the release of pro-inflammatory cytokines from immune cells by acting on nicotinic acetylcholine receptors (α7nAChRs). This neuroimmune modulation contributes to systemic homeostasis, linking autonomic regulation to immune resilience and helping prevent excessive or chronic inflammatory responses.
DIGESTION
The vagus modulates the enteric nervous system (ENS), which independently governs much of our of digestive function. While the ENS governs many aspects of digestion, vagal efferents influence gut motility, secretion of digestive enzymes, and coordination of sphincter activity. Vagal afferents continuously transmit sensory signals from the gastrointestinal tract to the brainstem, allowing for adaptive regulation of digestive activity. This bidirectional vagal communication supports not only efficient nutrient absorption and waste elimination but also links gastrointestinal function to emotional and autonomic states—a dynamic especially relevant in the context of Polyvagal Theory, which emphasizes how gut regulation is integrated into broader cues of safety and physiological state.
SPEECH
The vagus nerve contributes to speech by modulating vocal cord function and coordinating with respiratory rhythms, in concert with other cranial and cortical systems.
The Anatomy of the Vagus Nerve
For those interested in a more detailed anatomical look at the vagus, this diagram shows the full scope of the vagus nerve, including its branches to various organs and body parts.
The vagus nerve comprises two bilateral branches that emerge from the brainstem and converge above the chest cavity. While both branches share roles in autonomic regulation, they exhibit functional specializations—particularly in cardiovascular and digestive systems.
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The ventral vagal complex, along with cranial nerves V, VII, IX, X, and XI, orchestrates social behaviors such as vocal prosody, facial expression, and gaze (in Polyvagal Theory terms, our ‘social engagement system’).
Note on Pelvic Innervation:
The vagus nerve innervates thoracic and upper abdominal organs, while pelvic organ control is mediated by sacral spinal nerves (S2–S4). However, pelvic sensory input can influence vagal circuits indirectly through central autonomic pathways [6].
Caveat on Neuroanatomical Illustrations:
Please be advised that the illustrations linked in this resource are intended to support conceptual understanding of vagal pathways and their physiological functions. These images serve an educational purpose and may include artistic liberties for the sake of clarity or visual emphasis. As such, they should not be interpreted as anatomically precise or definitive representations of human neuroanatomy.
The depictions aim to highlight the broad functional scope of the vagus nerve and its involvement in autonomic regulation, consistent with the principles of Polyvagal Theory. However, for rigorous scientific or clinical reference, readers are encouraged to consult peer-reviewed neuroanatomical literature or source materials authored by recognized experts in the field.
​All vagus nerve illustrations by Alexis Cruz, © 2025 Polyvagal Institute. For educational use only; all rights reserved.
Vagus Nerve Stimulation
The vagus nerve can be stimulated through both natural behavioral practices and technological interventions. Natural methods—such as breath regulation, vocalization (e.g., singing, humming), yoga, and socially engaging behaviors—may activate afferent vagal pathways, particularly those associated with the ventral vagal complex, thereby supporting calm states, emotional regulation, and homeostasis.
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In addition to behavioral strategies, vagus nerve stimulation (VNS) can also be delivered via medical and wellness devices, which fall into two broad categories:
Implantable VNS (iVNS): Surgically implanted devices deliver electrical impulses to the cervical vagus nerve. iVNS is FDA-approved for conditions such as epilepsy, treatment-resistant depression, and stroke rehabilitation.
Non-invasive VNS (nVNS): These devices deliver mild electrical stimulation to afferent vagal fibers—often transcutaneously via the auricular branch of the vagus nerve (ABVN), a sensory pathway conveying somatosensory input from the external ear to the brainstem. Stimulation of this pathway has shown promise in enhancing parasympathetic activity (e.g., increased HRV), supporting emotional regulation, stress resilience, and reducing inflammation. Some nVNS devices are consumer-accessible and do not require a prescription. From a Polyvagal Theory perspective, taVNS may modulate brainstem circuits underlying the Social Engagement System by promoting vagal tone and physiological states conducive to safety and connection.
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While both iVNS and nVNS stimulate vagal afferents projecting to the NTS, the resulting effects depend on parameters such as stimulation frequency, anatomical site, and the individual’s autonomic state.
Non-Invasive VNS Options
Non-invasive vagus nerve stimulation (nVNS) devices are available on the market, some of which are supported by emerging research for potential roles in stress reduction and emotional regulation. Individuals interested in these technologies should consult scientific literature and qualified healthcare providers before use [5].
Recent comprehensive resources provide in-depth analyses of VNS applications:
Frasch, M.G., & Porges, E.C. (Eds.). (2023). Vagus Nerve Stimulation. Neuromethods, vol 205. Humana, New York, NY. https://doi.org/10.1007/978-1-0716-3465-3
Staats, P., Ayata, C., Lerman, I., & Abd-Elsayed, A. (Eds.). (2024). Vagus Nerve Stimulation. Academic Press. ISBN: 9780128169971
These texts delve into the mechanisms, clinical applications, and future directions of VNS, offering valuable insights for both clinicians and researchers.
Lifestyle Integration and Curated Devices
Natural methods of stimulating the vagus nerve—such as breathwork, vocalization, movement, and social engagement—are often free, low-cost, and easily integrated into daily life. These strategies support autonomic regulation and emotional balance by engaging the body’s intrinsic mechanisms for calming and recovery.For individuals seeking additional support, the Polyvagal Institute (PVI) has curated a selection of non-invasive vagus nerve stimulation (nVNS) devices that meet standards of safety, research validation, and alignment with the principles of Polyvagal Theory. [Coming Soon] is a list of recommended devices and programs, all of which are available on the consumer market and have been evaluated for their relevance to vagal activation and nervous system support.
The Superhighway of Homeostasis
Humans have 12 pairs of cranial nerves, with the vagus being the tenth, referred to as Cranial Nerve X. Its name comes from the Latin vagus, meaning ‘wandering’, as the nerve meanders from the base of the brain all the way down to the gut. It’s a bi-directional superhighway, carrying sensory information from the body to the brain (afferent nerves) and motor information from the brain to the body (efferent nerves).
Efferent fibers from the nucleus ambiguus, which give rise to the ventral vagal complex (VVC), provide myelinated, rapidly conducting parasympathetic output primarily to supradiaphragmatic structures, including the heart and the striated muscles of the face, head, pharynx, larynx, and upper esophagus. These fibers coordinate with other special visceral efferents via cranial nerves (V, VII, IX, X, XI) to regulate behaviors central to the Social Engagement System, such as vocal prosody, facial expression, and heart rate modulation. In contrast, unmyelinated efferents from the dorsal motor nucleus of the vagus (DVC) are the primary source of parasympathetic control over subdiaphragmatic organs, regulating functions such as digestion, metabolism, and gut motility.
The Vagus Nerve and the Social Engagement System (SES):
The SES is anchored in the VVC and coordinates with cranial nerves V, VII, IX, X, and XI. When neuroception detects safety, the VVC suppresses defense systems and promotes behaviors like vocal prosody, facial expression, and gaze stabilization. Trauma and chronic stress can inhibit the VVC, disrupting social signaling and emotional regulation.
The Autonomic Nervous System and Polyvagal Theory:
The autonomic nervous system maintains homeostasis through a dynamic balance between sympathetic activation and parasympathetic modulation. A core concept in Polyvagal Theory, the vagal brake refers to the ventral vagal system’s ability to reduce heart rate without requiring withdrawal of sympathetic tone—allowing rapid shifts in state in response to context.
RSA (a component of HRV) and vagal efficiency serve as indices of ventral vagal tone and responsiveness, reflecting how effectively the system can support calm and flexibility.
The vagus nerve can be functionally and anatomically differentiated across three interrelated dimensions:
1. Origin from distinct brainstem nuclei—the nucleus ambiguus (ventral vagal complex, VVC) and the dorsal motor nucleus of the vagus (dorsal vagal complex, DVC);
2. Lateralization of its left and right branches, which exhibit organ-specific asymmetries;
3. Topographic reach above and below the diaphragm, where ventral vagal fibers primarily innervate supradiaphragmatic structures (e.g., heart, lungs, pharynx), while dorsal vagal fibers predominantly innervate subdiaphragmatic viscera (e.g., stomach, intestines).
While the DVC is predominantly associated with abdominal innervation, it also exerts influence on supradiaphragmatic structures like the lower esophagus and portions of the heart, especially during threat-related or defensive states. Approximately 80% of the vagus nerve fibers are afferent, transmitting interoceptive feedback from visceral organs to the nucleus tractus solitarius (NTS), where this sensory input is integrated to support adaptive autonomic regulation. This anatomical-functional organization illustrates the hierarchical nature of vagal control, as articulated in Polyvagal Theory, with the VVC enabling flexible, reciprocal social behavior and the DVC supporting visceral homeostasis and defensive responses.
The Auricular Branch of the Vagus Nerve (ABVN):
The ABVN is a sensory afferent pathway originating from the superior (jugular) ganglion of the vagus. It conveys somatosensory signals from the outer ear to the NTS. Though not a motor component of SES, it can influence autonomic state and is the target of transcutaneous auricular vagus nerve stimulation (taVNS)—a non-invasive method with growing evidence for its role in stress and emotion regulation.
Questions about the Vagus Nerve?
Watch these Short Videos
Peter Staats, MD, researcher, President, Founder, and Chairman of The Vagus Nerve Society
answers some common questions about the vagus nerve in this series of short videos
References
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1. Porges, S.W. (2001). The Polyvagal Theory: Phylogenetic substrates of a social nervous system. International Journal of Psychophysiology, 42(2), 123–146.
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2. Tracey, K.J. (2002). The inflammatory reflex. Nature, 420(6917), 853–859.
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3. Frangos, E., Ellrich, J., & Komisaruk, B.R. (2015). Non-invasive access to the vagus nerve central projections via electrical stimulation of the external ear: fMRI evidence in humans. Brain Stimulation, 8(3), 624–636.
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4. Bonaz, B., Picq, C., Sinniger, V., Mayol, J.F., & Clarençon, D. (2013). Vagus nerve stimulation: from epilepsy to the cholinergic anti-inflammatory pathway. Neurogastroenterology & Motility, 25(3), 208–221.
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5. Yap, J.Y.Y., Keatch, C., Lambert, E., Woods, W., & Stoddart, P.R. (2020). Critical Review of Transcutaneous Vagus Nerve Stimulation: Challenges for Translation to Clinical Practice. Frontiers in Neuroscience, 14, 284.
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6. Breit, S., Kupferberg, A., Rogler, G., & Hasler, G. (2018). Vagus nerve as modulator of the brain–gut axis in psychiatric and inflammatory disorders. Frontiers in Psychiatry, 9, 44.