Key result
Transcutaneous auricular vagus nerve stimulation via the left tragus produced significantly greater BOLD signal increases in the right caudate and anterior cingulate compared to control stimulation.
Why the study?
Prior taVNS/fMRI studies yielded inconsistent findings regarding vagal network effects due to variability in stimulation targets and parameters.
Does transcutaneous auricular vagus nerve stimulation (taVNS) via left tragus stimulation alter BOLD signal on fMRI compared to earlobe stimulation in healthy adults?
RCT (n=17)
Single-blind
Does transcutaneous auricular vagus nerve stimulation (taVNS) via left tragus stimulation alter BOLD signal on fMRI compared to earlobe stimulation in healthy adults?
Transcutaneous auricular vagus nerve stimulation via the tragus activates cerebral afferents of the vagal pathway, demonstrating its potential as a neuromodulation technique.
taVNS/fMRI system may standardize stimulation assessment; leaves open optimal parameters for psychiatric translation.
Background: Electrical stimulation of the auricular branch of the vagus nerve (ABVN) via transcutaneous auricular vagus nerve stimulation (taVNS) may influence afferent vagal networks. There have been 5 prior taVNS/fMRI studies, with inconsistent findings due to variability in stimulation targets and parameters. Objective: We developed a taVNS/fMRI system to enable concurrent electrical stimulation and fMRI acquisition to compare the effects of taVNS in relation to control stimulation. Methods: We enrolled 17 healthy adults in this single-blind, crossover taVNS/fMRI trial. Based on parameters shown to affect heart rate in healthy volunteers, participants received either left tragus (active) or earlobe (control) stimulation at 500 μs 25 HZ for 60 s (repeated 3 times over 6 min). Whole brain fMRI analysis was performed exploring the effect of: active stimulation, control stimulation, and the comparison. Region of interest analysis of the midbrain and brainstem was also conducted. Results: Active stimulation produced significant increased BOLD signal in the contralateral postcentral gyrus, bilateral insula, frontal cortex, right operculum, and left cerebellum. Control stimulation produced BOLD signal activation in the contralateral postcentral gyrus. In the active vs. control contrast, tragus stimulation produced significantly greater BOLD increases in the right caudate, bilateral anterior cingulate, cerebellum, left prefrontal cortex, and mid-cingulate. Conclusion: Stimulation of the tragus activates the cerebral afferents of the vagal pathway and combined with our review of the literature suggest that taVNS is a promising form of VNS. Future taVNS/fMRI studies should systematically explore various parameters and alternative stimulation targets aimed to optimize this novel form of neuromodulation. (Appeared originally in Brain Stimulation 2018; 11:492–500) Reprinted with permission from Elsevier
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Badran et al. (2022) conducted an RCT in Healthy (n=17). Transcutaneous auricular vagus nerve stimulation (taVNS) via left tragus vs. Earlobe (control) stimulation was evaluated on BOLD signal changes on fMRI. Transcutaneous auricular vagus nerve stimulation via the left tragus produced significantly greater BOLD signal increases in the right caudate and anterior cingulate compared to control stimulation.
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