Autonomic and Neural Evaluation of the Dose Duration Response for Non-invasive Transcutaneous Auricular Vagus Nerve Stimulation

Transcutaneous auricular vagus nerve stimulation (taVNS) is a candidate non-invasive brain stimulation-based clinical tool for a variety of psychiatric disorders. Despite suggestion of promise, null effects and inconsistencies in reporting have also been accumulating, suggesting a need to evaluate stimulation parameters that lead to more replicable, meaningful effects. The goal of this study was to evaluate the effects of dose duration (15 to 75 active minutes) of taVNS across multiple modalities (autonomics and electrocortical activity) and processes (attentional engagement and executive function) in 28 healthy control participants. Results demonstrate that higher doses (60-75 minutes) of active taVNS were required to adaptively modulate heart rate variability during cognitive engagement - a dose significantly higher than those being administered across the literature. We also demonstrate that P300 in an oddball task did not modulate with increasing dose. These results indicate that taVNS may specifically modulate motivationally salient systems, though it is important to note that this could be due to a ceiling effect of P300 in the context of this healthy sample. To our knowledge this is the first ever dose duration finding study for taVNS and future investigations are needed to continue to narrow the parameter space and replicate these findings in a larger sample with psychiatric symptoms.