Transcutanenous auricular vagus nerve stimulation affects sustained attention in an order-dependent manner.

BackgroundSustained attention, the ability to remain focused during a task, relies on Locus coeruleus - Noradrenaline (LC-NA) activity. Noninvasive transcutaneous auricular vagus nerve stimulation (taVNS) is a promising tool to modulate LC-NA activity. We investigated the effects of taVNS on behavioral and electrophysiological markers of sustained attention during a Go-Nogo task. MethodsForty-four healthy participants (36 female) performed the gradual-onset Continuous Performance Task (gradCPT) on two days > 24 hours apart while EEG was recorded. 500 ms trains of taVNS or Sham stimulation was applied with each stimulus in a pseudorandomized fashion. Brain activity during the task was recorded with EEG. Behavioral and electrophysiological parameters of sustained attention were analyzed using (generalized) linear mixed models. ResultsWhen delivered during the first session, taVNS accelerated reaction times and enhanced fronto-central P1-N1 and parietal N1-P2 amplitudes. Larger P1-N1 amplitudes predicted faster responses, linking early cortical gain to behavioral performance. RT improvements persisted into the next-day sham session, whereas taVNS applied only during the familiar second session was ineffective. However, taVNS also increased RT variability, speaking against a general beneficial effect of taVNS on response automation. ConclusionWe show that taVNS modulates behavioral and electrophysiologial parameters of sustained attention and that this modulation depended on the applied stimulation order. These observations have important implications for future taVNS studies where the order of stimulation is counterbalanced across subjects.