Neural Correlates of Transcutaneous Vagal Nerve Stimulation: Functional MRI Effects of Anatomical Site and Waveform Parameters

Motivation: There is marked heterogeneity in transcutaneous vagal nerve stimulation (tVNS) based on the anatomical site (cervical/auricular), and the waveform parameters (fixed/variable frequency) of the stimulation. Goal(s): To explore the functional brain differences between cervical vagal nerve stimulation and auricular vagal nerve stimulation. Approach: Ultra-high field functional neuroimaging is performed of the neural correlates of tVNS with disparate anatomical sites and electrical waveform characteristics during rest in healthy participantsResults: Auricular stimulation with a variable frequency was shown to result in a significant decrease of the BOLD response in the amygdala and insular cortex compared to sham stimulation. Impact: There exist multiple knowledge gaps in the use of tVNS, which hinders the advancement of tVNS applications. This explorative study has shown the differences in neuronal response of auricular and cervical stimulation with fixed and variable frequencies.