Transcutaneous auricular vagus nerve stimulation regulates subjective fear in naturalistic contexts via modulation of prefrontal neural dynamics

Although non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) has demonstrated a therapeutic-relevant potential by enhancing mood recovery and fear extinction, its influence on neural dynamics during naturalistic, sustained fear processing remains unclear. In this study, we employed a randomized, sham-controlled, parallel-group design involving 63 participants (taVNS: n = 33; sham: n = 30) who provided continuous subjective fear ratings (1170 timepoints) while watching a 10-minute fear-inducing video, with simultaneous fNIRS recordings. We employed: (1) a convolutional neural network (CNN) to decode fear ratings from frontal activations, (2) validation of stimulus-evoked activity comparing fNIRS with fMRI signal, (3) dynamic conditional correlation analysis to assess taVNS-induced connectivity changes, and (4) moderation analysis to examine anxiety state effects. Behaviorally, taVNS significantly attenuated fear responses during four threat phases by content analysis: T1 (ghost appearance), T2 (escape sequence), T3 (sudden threat emergence) and T4 (suicide scene). Neurally, taVNS suppressed medial prefrontal cortex (mPFC) activation during escape (T2) and disrupted the typical fear coupling between fear experience and brain activity. Furthermore, taVNS enhanced intra-mPFC functional connectivity, suggesting a potential neural basis for modulating subjective threat appraisal. Additionally, state anxiety significantly moderated brain-behavior relationships. These findings demonstrate that taVNS attenuates fear responses through modulation of mPFC engagement and strengthening frontal network integration. Our results highlight taVNS as a promising neuromodulatory intervention for fear-related disorders (e.g., anxiety disorder), particularly as an early adjunct to exposure-based therapies, warranting further clinical validation.