Modulatory effects of transcutaneous auricular vagus nerve stimulation (taVNS) on attentional processes

Background The modulatory effect of transcutaneous auricular vagus nerve stimulation (taVNS) on attention has varied in previous studies. This inconsistency might be attributed to the combined influence of the modulation effect on the different attentional functions, including alerting, orienting and executive control.Aims We aimed to preliminarily examine the modulatory effects of taVNS on different attentional functions.Methods Fifty-nine healthy participants were recruited and were randomly assigned to taVNS (receiving taVNS for 20 minutes) or control (receiving taVNS for 30 seconds) groups. All participants underwent a dot-probe task before and after the taVNS/control intervention. Their behavioural performance and electroencephalographic signals during pre- and post-tests were recorded, and different observed variables were extracted and analysed to characterise different attentional systems.Results We observed that active taVNS applied at the left ear significantly improved the overall behavioural performance, that is, shorter reaction time (RT) and lower intra-individual reaction time variability (IIRTV) for right-hand responses when compared with the control condition. In addition, active taVNS resulted in larger P3 and movement-related cortical potential (MRCP) amplitudes associated with right-hand reactions than the control condition. Active taVNS also decreased the difference between the pre- and post-tests in the power spectral density of spontaneous high-α band oscillations at C4 electrode. Importantly, parallel mediation models for right-hand responses showed that the change of P3 amplitude mediated the effects of taVNS on RT and IIRTV. In contrast, the change of MRCP amplitude suppressed the effect of taVNS on the IIRTV.Conclusions Our results provided behavioural and brain evidence supporting the effects of taVNS on different attentional systems, and their interaction further shaped behavioural performance, suggesting a promising role of taVNS in cognitive enhancement.