Transcutaneous Auricular Vagus Nerve Stimulation: From Concept to Application

Abstract

Whether in the West or the East, the connection between the ear and the rest of the body has been explored for a long time. Especially in the past century or more, the relevant theoretical and applied research on the ear has greatly promoted the development of ear therapy, and finally the concept of transcutaneous auricular vagus nerve stimulation (taVNS) has been proposed. The purpose of taVNS is to treat a disease non-invasively by applying electrical current to the cutaneous receptive field formed by the auricular branch of the vagus nerve in the outer ear. In the past two decades, taVNS has been a topic of basic, clinical, and transformation research. It has been applied as an alternative to drug treatment for a variety of diseases. Based on the rapid understanding of the application of taVNS to human health and disease, some limitations in the development of this field have also been gradually exposed. Here, we comprehensively review the origin and research status of the field.

Keywords: Application; Concept; Development; Transcutaneous auricular vagus nerve stimulation.

Fig. 1

Numbers of publications on taVNS from 2000 to 2019.

Fig. 2

Potential mechanism of taVNS. A The external ear and its hypothesized cutaneous innervation by the ABVN. B Modulation of brain networks mainly depends on the extensive fibrous connections formed by ABVN projections to multiple brain regions through the NTS to regulate neuroendocrine, emotional, and cognitive functions. C The balance of the production of cytokines depends on the wiring of CAP [87, 88]. CNS, central nervous system; CAP, cholinergic anti-inflammatory pathway; VPM, ventralis posteromedialis nucleus; MIDLINE, midline thalamic nuclei; ILN, intralaminar nuclei; LC, locus coeruleus; RN, raphe nuclei; NTS, nucleus of the solitary tract; ABVN, auricular branch of the vagus nerve; taVNS, transcutaneous auricular vagus nerve stimulation; ACh, acetylcholine; α7nAChR, α7 nicotinic acetylcholine receptor; TNF, tumor necrosis factor; IL-1, interleukin-1.