# Label-Free Functional Imaging of Vagus Nerve Stimulation-Evoked Potentials at the Cortical Surface

## TL;DR

This study uses a new imaging method to observe brain responses to vagus nerve stimulation without labels or electrodes, helping improve epilepsy treatments.

## Contribution

A label-free, non-contact imaging technique to quantify vagus nerve stimulation-evoked cortical potentials.

## Key findings

- Stimulation amplitude strongly affects evoked potential magnitude (effect size 0.401).
- Pulse width moderately modulates responses (effect size 0.127), while frequency has minimal impact (effect size 0.009).
- Mild interaction is observed between pulse width and frequency.

## Abstract

Vagus Nerve Stimulation (VNS) was the first FDA-approved stimulation therapy to treat patients with refractory epilepsy and remains widely used. The mechanisms behind the therapeutic effect of VNS remain unknown but are thought to involve afferent-mediated modulation to cortical circuits 1. In this work, we use a coherent holographic imaging system to characterize vagus nerve evoked potentials (VEPs) in the cortex in response to typical VNS stimulation paradigms, which does not require electrode placement nor any genetic, structural, or functional labels. We find that stimulation amplitude strongly modulates VEPs response magnitude (effect size 0.401), while pulse width has a moderate modulatory effect (effect size 0.127) and frequency has almost no modulatory effect (effect size 0.009) on the evoked potential magnitude. We find mild interaction between pulse width and frequency. This non-contact label-free functional imaging technique could serve as a non-invasive rapid feedback tool to quantify VEPs and could increase the efficacy of VNS in patients with refractory epilepsy.