Analgesic Efficacy and Neural Mechanisms of Transcutaneous Auricular Vagus Nerve Stimulation in a Capsaicin-Induced Pain Model

Effective pain management remains a major clinical challenge. Transcutaneous auricular vagus nerve stimulation (taVNS) has emerged as a promising, non-invasive neuromodulation technique due to its safety, ease of administration, and cost-effectiveness. Preliminary evidence suggests that taVNS exerts analgesic effects by activating afferent vagal fibers, which integrate signals in key central nodes such as the nucleus tractus solitarius (NTS). This process subsequently modulates pain-processing networks, neurotransmitter balance, inflammatory responses, and autonomic function.

Despite its potential, the precise central neural mechanisms underlying taVNS-induced analgesia remain unclear, limiting the optimization of stimulation parameters (e.g., intensity, frequency, and target specificity) and the enhancement of long-term therapeutic outcomes. Previous studies have highlighted the role of taVNS in activating descending pain inhibitory pathways and modulating the limbic system, yet a comprehensive understanding of the causal neurophysiological dynamics is still lacking.

This study aims to investigate the analgesic efficacy of taVNS using a capsaicin-induced pain model. Furthermore, by employing Transcranial Magnetic Stimulation combined with Electroencephalography (TMS-EEG), we seek to elucidate the central neural mechanisms of taVNS. By integrating causal intervention with high-temporal resolution brain activity recording, this research will provide scientific insights into the modulation of pain-related pathways-such as descending inhibitory and cognitive-affective networks-ultimately facilitating the development of standardized, individualized, and precise clinical interventions for pain management.