# Neurobiological Mechanisms of Enhanced Pain-Relieving Transcutaneous Electrical Nerve Stimulation via Visuo-Tactile Stimulation in Immersive Virtual Reality: Randomized Controlled Trial

## TL;DR

This study explores how combining electrical nerve stimulation with immersive virtual reality can enhance pain relief and identifies the brain mechanisms involved.

## Contribution

The study introduces a novel integration of transcutaneous electrical nerve stimulation with personalized visuo-tactile feedback in immersive virtual reality.

## Key findings

- TENS combined with congruent VR showed greater pain reduction than TENS alone.
- TENS-ConVR reduced brain oscillation in the gamma band, unlike TENS alone.
- Stronger pain relief correlated with stronger reductions in brain activity.

## Abstract

Enhancing the effectiveness of current pain relief strategies is a persistent clinical challenge. Although transcutaneous electrical nerve stimulation (TENS) is used in various painful conditions, its effectiveness may decline over time, requiring additional pain management strategies. Immersive virtual reality (VR) with personalized visuo-tactile stimulation has demonstrated analgesic properties. Nevertheless, whether visuo-tactile stimulation can enhance the pain-relieving outcomes of TENS and its underlying neurophysiological mechanisms remains largely unknown.

The study aims to investigate whether the integration of visuo-tactile stimulation with TENS can enhance the pain-relieving outcomes of TENS alone, and we also aim to explore the brain mechanisms underlying the analgesic effect of this integrated intervention.

In this study, 75 healthy participants were enrolled and randomly assigned to 1 of 3 groups: congruent TENS-VR (TENS-ConVR) and 2 control groups (incongruent TENS-VR [TENS-InVR] and TENS alone). In the context of TENS-ConVR, we combined TENS and VR by connecting TENS-induced paresthesia with personalized visual bodily feedback. The visual feedback was designed to align with the spatiotemporal patterns of the paresthesia induced by TENS. A pain rating task and a 32-channel electroencephalography were applied.

Two-way ANOVAs showed that TENS-ConVR exhibited a statistically greater reduction in pain rating (F1,48=6.84; P=.01) and N2 amplitude (F1,48=5.69; P=.02) to high-intensity pain stimuli before and after stimulation than TENS alone. The reduction of brain activity was stronger in participants who reported stronger pain-relieving outcomes. TENS-ConVR reduced the brain oscillation in the gamma band, whereas this result was not found in TENS alone.

This study observed that combining TENS and visual stimulation in a single solution could enhance the pain-relieving effect of TENS, which has the potential to improve the effectiveness of current pain management treatments.

Chinese Clinical Trial Registry ChiCTR2500098834; https://www.chictr.org.cn/showprojEN.html?proj=254171