Ultrasound transcutaneous auricular vagus nerve stimulation enhances semantic processing

Efficient access to conceptual knowledge is central to everyday cognition, yet the effects of non-invasive neuromodulation on semantic retrieval remain insufficiently characterised. Transcutaneous auricular vagus nerve stimulation (taVNS) offers a mechanistically distinct route to modulate distributed cognitive systems via ascending vagal afferent pathways, but its effects on semantic processing has not been explored. Here, we tested whether ultrasound-based taVNS delivered to the right cymba conchae can acutely enhance semantic retrieval efficiency in healthy adults. Twenty-seven participants completed a single blind, sham-controlled study comprising two counterbalanced sessions (active vs. sham) in a within-subject design, separated by at least five days. In each session, participants performed a semantic association task and a number-judgement control task before and immediately after 30 minutes of stimulation. Active taVNS produced selective post-stimulation improvements in semantic retrieval performance relative to sham and baseline, while performance on the control task remained unchanged. Adverse effects were minimal and did not differ between active and sham conditions. These findings provide causal evidence that ultrasound-based taVNS can acutely improve the efficiency of semantic processing, expanding the cognitive profile of taVNS beyond predominantly episodic and emotional memory domains and supporting its feasibility as a scalable approach for memory enhancement.