Non-invasive Ultrasonic Auricular Vagus Nerve Stimulation

The Vagus nerve, one of 12 cranial nerves that connect the brain to the human body, controls specific involuntary functions such as breathing, heart rate, the digestive system and the immune system, and it is crucial to unlocking the relaxation response (parasympathetic nervous system). Vagus nerve stimulation (VNS) can be invasive or non-invasive, and both methods have been trialled in research studies. Some non-invasive VNS involves the use of a device which is placed on the skin, to send electrical impulses to the Vagus nerve. The device sends electrical impulses to some areas of the brain which changes brain activity and helps in treating certain disorders. Invasive methods utilise a surgically implanted Vagus nerve stimulator on the left Vagus nerve in the neck area. VNS is used in treatment of epilepsy and studies has shown to have a therapeutic effect on treatment resistant depression. Currently, research indicates that invasive VNS to treat anxiety yield mixed results, whilst other studies suggest that VNS with exposure-based therapies might enhance outcomes for anxiety patients. Stimulating the Vagus nerve comes with serious technical challenges. Most importantly, electric currents follow the path of least resistance. When running through biological tissues, such as skin, cartilage or bone, it is difficult to aim for the part of the body that needs to be stimulated. This means it isn't always easy to tell whether the Vagus nerve is indeed being stimulated and how much of the current is reaching the Vagus nerve. This problem can be overcome by ultrasound stimulation. Ultrasound stimulation employs high frequency sound waves to stimulate tissue. These soundwaves travel through the human body much more predictably than electric currents. As such, ultrasound stimulation of the Vagus nerve may be more effective than electrical stimulation. The ZenBud device is designed to apply ultrasound stimulation to part of the auricular branch of the Vagus nerve. Ultrasound stimulation allows for more targeted stimulation, increasing the chance of the stimulation reaching the Vagus nerve. The ZenBud device is safe for use in healthy adults and received CE marking. Before testing the therapeutic effect of the Zenbud on patients with symptoms it is important to identify physiological, cognition or emotional changes in health volunteers. Identifying these changes could lead to identifying possible future therapeutic uses for ultrasound-VNS (U-VNS).