Comparing Electrical and Ultrasound Transcutaneous Auricular Vagus Nerve Stimulation on Associative Memory

OBJECTIVES: Associative memory, the ability to bind and retrieve relationships between unrelated elements, is a cornerstone of human cognition and a primary target for neurorehabilitation. Vagus nerve stimulation (VNS) has emerged as a promising method to modulate the locus coeruleus-norepinephrine system and hippocampal-prefrontal circuits essential for memory. However, the comparative efficacy of noninvasive modalities such as electrical transcutaneous VNS (E-taVNS) and the emerging field of ultrasound (U-taVNS) remains poorly understood in the context of active recall. MATERIALS AND METHODS: In this study, participants performed a cross-modal video-word associative memory task before and after receiving either E-taVNS or U-taVNS in active and sham conditions. We investigated whether these modalities enhance cued recall accuracy and retrieval reaction time. RESULTS: Our results revealed that neither E-taVNS nor U-taVNS significantly improved recall accuracy. However, E-taVNS significantly accelerated response times specifically for correctly recalled items. These findings suggest that although taVNS may not increase the likelihood of recalling associative memories after a brief retention interval, electrical stimulation may enhance the efficiency with which we do so. CONCLUSIONS: These findings suggest that E-taVNS is a viable tool for facilitating memory processes, although further research is required to optimize ultrasound parameters and validate mechanistic pathways through physiologic monitoring.