The Autonomic Nervous System

When you think about your nervous system, you probably think about the brain and how it controls your thoughts and movements.

However, there’s another part of your nervous system that works behind the scenes to regulate functions that you don’t consciously control. This is known as the autonomic nervous system (ANS).


What is the Autonomic Nervous System?

The ANS is like the backstage crew of a theater production, running the show without being seen. It manages functions like your heart rate, breathing, digestion, and body temperature — processes that happen automatically without you needing to think about them.

The autonomic nervous system is further divided into two primary parts: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS).

Sympathetic Nervous System

Ready for Action

Think of the sympathetic nervous system as the ‘fight or flight’ manager. It prepares your body to respond to emergencies or vigorous activity. When the SNS is activated, your heart rate speeds up, your pupils dilate, and your body releases adrenaline to help you react quickly. It’s like the alarm system that gets your body ready to face danger or tackle physical challenges.

Parasympathetic Nervous System

Rest and Relax

On the other side of the coin, the parasympathetic nervous system is like the ‘rest and digest’ caretaker. It takes over once the perceived danger has passed, helping your body calm down and return to a relaxed state. It slows your heart rate, aids digestion, and allows your body to recover and repair. The PNS can be seen as the ‘chill-out’ system that promotes relaxation and rejuvenation.

Vagus Nerve Stimulation Research & History

  • 1. History of Vagus Nerve Stimulation Research

    The study of vagus nerve stimulation (VNS) has come a long way since its early stages, progressing from rudimentary observations to sophisticated therapeutic applications.

  • 2. Early Discoveries

    The importance of the vagus nerve was first recognized in the 19th century. German physician Friedrich Goltz observed that heart rate could be slowed by stimulating the vagus nerve, a discovery that was later developed by physiologist Otto Loewi in the early 20th century. Loewi’s work, which demonstrated that the vagus nerve released a substance he named ‘Vagusstoff’ (later identified as acetylcholine) to slow the heart, won him the Nobel Prize in Medicine in 1936.

  • 3. Birth of VNS Therapy

    The idea of using vagus nerve stimulation as a treatment for health conditions originated in the late 20th century. In 1985, a team led by Jacob Zabara found that VNS could prevent or reduce the severity of seizures in dogs, opening up a new avenue for epilepsy treatment.The development of VNS as a therapy moved quickly. By 1997, the US Food and Drug Administration (FDA) had approved a VNS device for treating epilepsy. This device, made by Cyberonics (now LivaNova), was implanted in the chest and sent regular electrical impulses to the vagus nerve via a lead in the neck.

  • 4. Expanding Applications

    In the early 2000s, researchers began to explore the potential use of VNS in treating psychiatric conditions. After several studies showed positive effects, the FDA approved VNS therapy for treatment-resistant depression in 2005.The potential applications for VNS continued to expand, with researchers investigating its use for a variety of conditions, such as chronic pain, obesity, migraines, and even Alzheimer’s disease. Many of these studies are still ongoing.

  • 5. Recent Advances

    More recent research has focused on non-invasive VNS methods. These include transcutaneous VNS, which stimulates the vagus nerve through the skin, and transcranial VNS, which uses magnetic fields to stimulate the nerve.In the 2020s, companies like the ultrasound neuromodulation company behind the Zenbud began exploring ultrasound technology as a means of stimulating the vagus nerve. This non-invasive approach avoids the need for surgical implantation and can be administered more easily and comfortably.

  • 6. Conclusion

    From its early discovery in the 19th century to the innovative, non-invasive technologies of today, vagus nerve stimulation has a rich history rooted in curiosity, scientific ingenuity, and a dedication to improving human health. As we continue to unravel the intricacies of the vagus nerve and the autonomic nervous system, the possibilities for VNS therapy continue to expand.

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  • The ZenBud: A leap in VNS technology

    The ZenBud is the cutting edge technology. As the first ever ultrasound vagus nerve stimulator on the ear, it represents a new era of vagus nerve stimulation technology.

Read the Science!

VNS for Stress (Bremner et al., 2020)

Vagal Nerve Stimulation (VNS) has been shown to be efficacious for the treatment of depression, but to date, VNS devices have required surgical implantation, which has limited widespread implementation.


VNS for Mood (Fersti et al., 2021)

Mood plays an important role in our life which is illustrated by the disruptive impact of aberrant mood states in depression. Although vagus nerve stimulation (VNS) has been shown to improve symptoms of depression, the exact mechanism is still elusive, and it is an open question whether non-invasive VNS could be used to swiftly and robustly improve mood.


VNS for HRV and Well-being (Machetanz et al., 2021)

Non-invasive vagus nerve stimulation is fast becoming a popular alternative treatment method for various
health disorders. The authors investigated the effects of auricular vagus nerve stimulation at tragus for activating the parasympathetic nervous system to reduce stress, in light of mixed results from other studies. Stimulation frequency of 25 Hz with a pulse-width of 200 µs was administered at tragus with ECG data recorded
during pre- and post-stimulation trials to investigate changes in the low-frequency (LF) and high-frequency
(HF) parameters of heart rate variability (HRV).


Research proves that VNS reduces stress and combats PTSD. (Mouli et al., 2021)

Transcutaneous auricular vagus nerve stimulation (taVNS) modulates central and peripheralneurophysiology. Specifically, taVNS increases heart rate variability (HRV) indicating a shift inautonomic functiontowards parasympathetic predominance. However, knowledge on the influence of stimulation parameters and targets is scarce. We hypothesized that the location and charge per phase of taVNS influences HRV.


A systematic Review of Ultrasound Stimulation of the Brain (Sarica Et Al. 2022)

Transcranial ultrasound stimulation (TUS) is gaining traction as a safe and non-invasive technique in human studies. There has been a rapid increase in TUS human studies in recent years, with more than half of studies to date published after 2020. This rapid growth in the relevant body of literature necessitates comprehensive reviews to update clinicians and researchers.


Non-invasive Ultrasound Neuromodulation (Bowary Et Al. 2018)

Focused ultrasound (FUS) has been of research and potential clinical interest as a neuromodulation method for over half a century.12345However, over the past decade the interest in this technique has increased dramatically. High-intensity focused ultrasound (HIFU) is an approved technique for ablation of specific brain targets in the treatment of essential tremor67and chronic pain.