The effects of non-invasive transcutaneous auricular vagus nerve stimulation on resting-state delta oscillation: a randomized, double-blinded, sham-control trial

Transcutaneous auricular vagus nerve stimulation (taVNS) is a promising technique that potentially influences cortical activity, mainly increasing electroencephalography (EEG) power spectrum activity in low-frequency oscillations, and demonstrates potential therapeutic benefits for various pathologic conditions, like depression and chronic pain. To learn further about taVNS brain mechanisms, the present study investigated how using a single taVNS session can affect brain oscillations in healthy subjects. 44 healthy participants were included in this randomized, double-blind, sham-controlled trial. Participants were divided into the active and sham taVNS groups. Resting-state EEG power was analyzed across the frontal, central, and parietal regions in both hemispheres. Our findings demonstrated that active taVNS modulates low-frequency oscillations in the frontal areas of healthy subjects. After the intervention, the average delta power at the frontal region increased in the active group compared to the sham group. These changes were also observed with an increase in delta asymmetry (towards the right hemisphere) in the active group compared to the sham group. In healthy subjects, active taVNS selectively induces changes in the resting-state frontal brain oscillations. Our results suggest that taVNS increases homeostatic low-frequency oscillatory activity mainly over the right frontal hemisphere. Active taVNS induces activation of the fronto-vagal network, which has a therapeutic potential to generate salutogenic and balanced brain activity.