Background Pursuing goals is compromised when being confronted with interfering information. In such situations conflict monitoring is important. Theoretical considerations on the neurobiology of response selection and control suggest that auricular transcutaneous vagus nerve stimulation (atVNS) should modulate conflict monitoring. However, the neurophysiological-functional neuroanatomical underpinnings are still not understood. Methods AtVNS was applied in a randomized crossover study design (N=45). During atVNS or sham stimulation, conflict monitoring was assessed using a Flanker task. EEG data were recorded and analyzed with focus on theta and alpha band activity. Beamforming was applied to examine functional neuroanatomical correlates of atVNS-induced EEG modulations. Moreover, temporal EEG signal decomposition was applied to examine different coding level in alpha and theta band activity. Results AtVNS compromised conflict monitoring processes, when atVNS was applied at the second appointment in the crossover study design. On a neurophysiological level, atVNS exerted specific effects since only alpha-band activity was modulated. Alpha-band activity was lower in middle and superior prefrontal regions during atVNS stimulation and thus lower when there was also a decline in task performance. The same direction of alpha-band modulations was evident in fractions of the alpha-band activity coding stimulus-related processes, stimulus-response translation processes, and motor response-related processes. Conclusions The combination of prior task experience and atVNS compromises conflict monitoring processes. This is likely due to reduction of alpha-band associated inhibitory gating process on interfering information in frontal cortices. Future research shall pay considerable attention to boundary conditions affecting the direction of atVNS effects.

Alcohol use disorder (AUD) is a relapsing–remitting condition characterized by excessive and/or continued alcohol consumption despite harmful consequences. New adjuvant tools, such as noninvasive brain stimulation techniques, might be helpful additions to conventional treatment approaches or even provide an alternative option for patients who fail to respond adequately to other treatment options. Here, we discuss the potential use of auricular transcutaneous vagus nerve stimulation (atVNS) as an ADD‐ON intervention in AUD. Compared with other techniques, atVNS has the advantage of directly stimulating nuclei that synthesize GABA and catecholamines, both of which are functionally altered by alcohol intake in AUD patients. Pharmacological options targeting those neurotransmitters are widely available, but have relatively limited beneficial effects on cognition, even though restoring normal cognitive functioning, especially cognitive control, is key to maintaining abstinence. Against this background, atVNS could be a particularly useful add‐on because there is substantial meta‐analytic evidence based on studies in healthy individuals that atVNS can enhance cognitive control processes that are crucial to regaining control over drug intake. We discuss essential future research on using atVNS as an ADD‐ON intervention in AUD to enhance clinical and cognitive outcomes by providing a translational application. Given that this novel technique can be worn like an earpiece and can be employed without medical supervision/outside the clinical settings, atVNS could be well integratable into the daily life of the patients, where the task of regaining control over drug intake is most challenging.

Everyday tasks and goal-directed behavior involve the maintenance and continuous updating of information in working memory (WM). WM gating reflects switches between these two core states. Neurobiological considerations suggest that the catecholaminergic and the GABAergic are likely involved in these dynamics. Both of these neurotransmitter systems likely underly the effects to auricular transcutaneous vagus nerve stimulation (atVNS). We examine the effects of atVNS on WM gating dynamics and their underlying neurophysiological and neurobiological processes in a randomized crossover study design in healthy humans of both sexes. We show that atVNS specifically modulates WM gate closing and thus specifically modulates neural mechanisms enabling the maintenance of information in WM. WM gate opening processes were not affected. AtVNS modulates WM gate closing processes through the modulation of EEG alpha band activity. This was the case for clusters of activity in the EEG signal referring to stimulus information, motor response information and fractions of information carrying stimulus-response mapping rules during WM gate closing. EEG-beamforming shows that modulations of activity in fronto-polar, orbital and inferior parietal regions are associated with these effects. The data suggest that these effects are not due to modulations of the catecholaminergic (noradrenaline) system as indicated by lack of modulatory effects in pupil diameter dynamics, in the inter-relation of EEG and pupil diameter dynamics and saliva markers of noradrenaline activity. Considering other findings, it appears that a central effect of atVNS during cognitive processing refers to the stabilization of information in neural circuits, putatively mediated via the GABAergic system.Significance statement:Goal-directed behavior depends on how well information in short-term memory can be flexibly updated but also on how well it can be shielded from distraction. These two functions were guarded by a working memory gate. We show how an increasingly popular brain stimulation techniques (atVNS) specifically enhances the ability to close the WM gate to shield information from distraction. We show what physiological and anatomical aspects underlie these effects.

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