Transcutaneous auricular vagus nerve stimulation: mechanisms, applications, and research progress.

This review systematically examines the mechanisms of action, optimization of stimulation parameters and targets, and the research progress in the application of taVNS for neurological disorders and systemic conditions. Rather than merely cataloging existing findings, this review critically synthesizes recent advances with a focused emphasis on two core aspects: (1) the mechanistic convergence and divergence among neuroimaging, autonomic, and molecular pathways underlying taVNS effects; and (2) the methodological challenges and biomarker-driven strategies for optimizing stimulation parameters and personalizing treatment. By prioritizing these key directions over exhaustive enumeration of clinical applications, this review aims to provide a conceptually structured framework that distinguishes genuine progress from descriptive accumulation. Moreover, compared with previously published reviews on similar topics, the present work offers a distinctive contribution by integrating multi-modal mechanistic evidence into a testable model of taVNS action and critically evaluating the translational gap between parametric optimization in research settings and standardized clinical implementation. Furthermore, it provides an outlook on future research directions and technological developments, aiming to offer a comprehensive theoretical framework to inform both clinical translation and foundational research in this rapidly evolving field.