The Impact of Transcutaneous Auricular Vagus Nerve Stimulation on Human Cognitive and Affective Processes: A PRISMA Systematic Review

Cognitive and affective processes jointly underwrite human well-being; their neurobiological implementation—via distributed cortico–subcortical circuits coupled to autonomic control through the vagus nerve—provides a plausible entry point for non-invasive modulation. Transcutaneous auricular vagus nerve stimulation (taVNS) leverages this pathway and shows promise, yet protocols and outcomes remain heterogeneous. We conducted a PRISMA-guided systematic review (PROSPERO: 1123821), searching six databases through April 2025 for controlled human studies without diagnosed pathology that compared taVNS with sham or active control and reported cognitive or affective outcomes. Two reviewers independently screened and extracted data. Of 1,291 records identified, 32 studies met eligibility and were synthesized narratively across four domains: attention, affective dimension, learning, and higher-order executive functions. In attention, taVNS often improved decision accuracy or conflict adaptation and increased pupil-linked arousal, with limited effects on reaction time, though several studies were null. In the affective dimension, taVNS reduced symptoms in some samples and modulated sleep architecture and emotion-related neurophysiology, but results were mixed. During learning, taVNS facilitated extinction memory and enhanced probabilistic reinforcement accuracy, while physiological fear markers showed inconsistent modulation. For higher-order executive functions, taVNS improved motor preparation and divergent thinking and sometimes enhanced post-error or post-conflict adjustments; other trials showed neural changes without behavioral gains or yielded null/adverse effects. Overall, the strongest evidence arises when behavioral benefits co-occur with convergent autonomic or neural modulation, yet heterogeneity in montage, dosing, and tasks limits inference. taVNS appears feasible and capable of modulating processes relevant to cognitive–affective balance; establishing when, for whom, and under what conditions it is beneficial will require harmonized protocols and confirmatory trials. Limitations include small, predominantly healthy samples; variable blinding and controls; inconsistent parameter/outcome reporting; and reliance on narrative synthesis without meta-analysis.