Electroencephalographic Patterns in taVNS: A Systematic Review

Abstract

Transcutaneous auricular vagus nerve stimulation (taVNS) is a newer delivery system using a non-invasive stimulation device placed at the ear. taVNS research is focused on clinical trials showing potential therapeutic benefits, however the neurophysiological effects of this stimulation on brain activity are still unclear. We propose a systematic review that aims to describe the effects of taVNS on EEG measures and identify taVNS parameters that can potentially lead to consistent EEG-mediated biomarkers for this therapy. A systematic literature review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) and the Cochrane handbook for systematic reviews. Clinical trials examining EEG parameters were considered, including absolute and relative power, coherence, degree of symmetry, evoked potentials, and peak frequency of all bands. According to our criteria, 18 studies (from 122 articles) were included. Our findings show a general trend towards increased EEG power spectrum activity in lower frequencies, and changes on early components of the ERP related to inhibitory tasks. This review suggests that quantitative electroencephalography can be used to assess the effects of taVNS on brain activity, however more studies are needed to systematically establish the specific effects and metrics that would reflect the non-invasive stimulation through the auricular branch of the vagus nerve.

Antipsychotics-Induced Changes in Synaptic Architecture and Functional Connectivity: Translational Implications for Treatment Response and Resistance

“…Even though there are several methods to explore the impact of antipsychotic drugs on brain functional connectivity in preclinical models, two are the most widely applied: functional magnetic resonance imaging (fMRI) and, on the other hand, electrophysiology/electroencephalogram (EEG), which assess interregional patterns of co-activation and neuronal synchrony by measuring brain blood flow and electrical activity, respectively [ 114 , 115 , 116 ].…”

tVNS in Stroke: A Narrative Review on the Current State and the Future

“…Various neurophysiological metrics have been studied as potential biomarkers of tVNS and have recently been extensively reviewed. 81 While there has been interest in the P300 event-related potential as a marker of LC-noradrenergic signaling, this has not reliably been found to change with taVNS. 72 Fifth, tVNS should be paired with different rehabilitative strategies to target specific domains of upper limb function such as strength training, dexterity tasks, passive stretching, and sensory training to identify which aspects of arm function respond most favorably to tVNS.…”

Understanding the Neuroplastic Effects of Auricular Vagus Nerve Stimulation in Animal Models of Stroke: A Systematic Review and Meta-Analysis

“…For instance, a recent systematic review performed by our group has demonstrated the taVNS electroencephalographic effects current stage of evidence and the lack of homogenous studies and standardized metrics in the field. 9 Thus, well designed, and multimodal mechanistic studies to explore the ways that taVNS works are required. A possible mechanism that has been studied recently is the modulatory effects of vagus stimulation in the cholinergic anti-inflammatory pathway, the microbiota-gut-brain axis, or the hypothalamic-pituitary-adrenal axis.…”

“…7,8 Recent systematically reviewed results, on the aVNS's electroencephalographic effects, suggests the capability of aVNS in modulate cortical activity. 9 Furthermore, aVNS has been investigated in a variety of conditions, such as epilepsy, tinnitus, depression, Alzheimer's disease, Schizophrenia, pain, migraine, and Parkinson's disease, being considered safer, more accessible, and less invasive alternative than the surgical device. [9][10][11][12] Currently, animal studies seem to be having positive results regarding the reestablishment of motor function in rats with post stroke sequelae after aVNS.…”

“…9 Furthermore, aVNS has been investigated in a variety of conditions, such as epilepsy, tinnitus, depression, Alzheimer's disease, Schizophrenia, pain, migraine, and Parkinson's disease, being considered safer, more accessible, and less invasive alternative than the surgical device. [9][10][11][12] Currently, animal studies seem to be having positive results regarding the reestablishment of motor function in rats with post stroke sequelae after aVNS. [13][14][15][16][17][18][19][20][21][22] However, there is a lack of full understanding and categorization of the current evidence, especially regarding the mechanisms behind aVNS's effects that can be further analyzed.…”