Transcutaneous Auricular Vagus Nerve Stimulation to Improve Emotional State

Abstract

Emotional experiences are a part of our lives. The maladaptive functioning of an individual's emotional field can lead to emotional disturbances of various kinds, such as anxiety and depression. Currently, there is an increasing prevalence of emotional disorders that cause great human suffering and high socioeconomic costs. Emotional processing has a biological basis. The major neuroscientific theories of emotion are based on biological functioning, and all of them take into account the anatomy and function of the tenth cranial nerve: the vagus nerve. The vagus nerve connects the subdiaphragmatic and supradiaphragmatic areas and modulates emotional processing as the basis of interoceptive functioning. Auricular vagus nerve stimulation is a new and innovative neuromodulation technique based on the function of the vagus nerve. Several interventions have shown that this new neurostimulation technique is a very promising resource for treating emotional disorders. In this paper, we summarise three neuroscientific theories of emotion, explain what transcutaneous auricular nerve stimulation is, and present arguments for its use and continued research.

Keywords: emotion; emotional disorders; neuromodulation; transcutaneous auricular vagus nerve stimulation.

Figure 1

Generation of the emotional experience. Generating emotional experiences. The key to emotional experiences is the integration of perceptual and memory signals with signals related to brain and body states to form situational, self, and emotional schemas. These merge into an unconscious, or more accurately, a preconscious mental model of the emotional situation. The result of the model is a narrative that constitutes the penultimate preconscious antecedent of conscious emotional experience and is also the antecedent of verbal self-report. Adapted from LeDoux [11].

Figure 2

taVNS device. The image shows the electrodes located in the areas innervated by the auricular vagus nerve. Adapted from Warren et al. [59].

Figure 3

Auricular branch of the vagus nerve. ABVN: auricular branch of vagus nerve. ATN: auricular temporal nerve. GAN: great auricular nerve. The purple areas correspond to those of the auricular vagus nerve. Adapted from Butt et al. [54].

Figure 4

Brain and body projections of the vagus nerve. (A) Illustration of the connection between the brain and major body organs via the vagus nerve. (B) Brain areas involved in the vagal afferent pathway. Nucleus of the solitary tract (NTS), hypothalamus (Hyp), amygdala (amy), hippocampus (Hippo), cingulate cortex (Cing), orbital frontal cortex (OFC), and prefrontal cortex (PFC). (C) Distribution of the vagus nerve in the external ear. Adapted from Zhu et al. [87].