No abstract

Given its non-invasive nature, there is increasing interest in the use of transcutaneous vagus nerve stimulation (tVNS) across basic, translational and clinical research. Contemporaneously, tVNS can be achieved by stimulating either the auricular branch or the cervical bundle of the vagus nerve, referred to as transcutaneous auricular vagus nerve stimulation(VNS) and transcutaneous cervical VNS, respectively. In order to advance the field in a systematic manner, studies using these technologies need to adequately report sufficient methodological detail to enable comparison of results between studies, replication of studies, as well as enhancing study participant safety. We systematically reviewed the existing tVNS literature to evaluate current reporting practices. Based on this review, and consensus among participating authors, we propose a set of minimal reporting items to guide future tVNS studies. The suggested items address specific technical aspects of the device and stimulation parameters. We also cover general recommendations including inclusion and exclusion criteria for participants, outcome parameters and the detailed reporting of side effects. Furthermore, we review strategies used to identify the optimal stimulation parameters for a given research setting and summarize ongoing developments in animal research with potential implications for the application of tVNS in humans. Finally, we discuss the potential of tVNS in future research as well as the associated challenges across several disciplines in research and clinical practice.

The dynamic adaptation of cognitive control in the face of competition from conflicting response tendencies is one of the hallmarks of flexible human action control. Here, we suggest an alternative framework that places conflicttriggered control adaptation into the broader context of affect regulation. Specifically, we review evidence showing that (a) conflicts are inherently aversive, that (b) aversive stimuli in the absence of conflict also trigger behavioral adjustments, and, finally, that (c) conflict stimuli do trigger processes of affective counter-regulation. Together with recent findings showing that conflict-triggered control adaptation depends on the subjective experience of the conflict, we suggest that it is the subjective aversive conflict experience that originally motivates control adaptations. Such a view offers new perspectives for investigating and understanding intra-and interindividual differences in the regulation of cognitive control by differentiating between the individual sensitivity to experience and the individual ability to utilize the aversive signal.

In the context of performance optimizations in multitasking, a central debate has unfolded in multitasking research around whether cognitive processes related to different tasks proceed only sequentially (one at a time), or can operate in parallel (simultaneously). This review features a discussion of theoretical considerations and empirical evidence regarding parallel versus serial task processing in multitasking. In addition, we highlight how methodological differences and theoretical conceptions determine the extent to which parallel processing in multitasking can be detected, to guide their employment in future research. Parallel and serial processing of multiple tasks are not mutually exclusive. Therefore, questions focusing exclusively on either task-processing mode are too simplified. We review empirical evidence and demonstrate that shifting between more parallel and more serial task processing critically depends on the conditions under which multiple tasks are performed. We conclude that efficient multitasking is reflected by the ability of individuals to adjust multitasking performance to environmental demands by flexibly shifting between different processing strategies of multiple task-component scheduling.

Dynamically adjusting the right amount of goal shielding to varying situational demands is associated with the flexibility of cognitive control, typically linked with pFC functioning. Although stress hormones are found to also bind to prefrontal receptors, the link between stress and cognitive control remains elusive. Based on that, we aimed at investigating effects of acute psychosocial stress on dynamic control adjustments. Forty-eight healthy volunteers were exposed to either a well-established stress induction protocol (the Trier Social Stress Test, TSST) or a standardized control situation before a selective attention (Simon) task involving response conflicts. The individual physiological stress response was monitored by analyzing levels of free cortisol and α-amylase activity in saliva samples showing that the TSST reliably induced an increase of endogenous stress hormone levels. Acute stress did not inevitably impair cognitive functioning, however, as stressed participants showed tonically increased goal shielding (to reduce interference) at the expense of decreased cognitive flexibility. Importantly, as a novel finding in humans, stress effects on cognitive functions were not present immediately after the stress experience but developed gradually over time and, therefore, paralleled the time course of the hypothalamus-pituitary-adrenal (HPA) stress response. In addition, the total increase of individual cortisol levels reflecting HPA activity, but not the total changes in α-amylase activity associated with sympathetic activity, was reversely related to the amount of cognitive flexibility in the final block of testing. Our study provides evidence for a stress-induced time-dependent decrease of cognitive flexibility that might be related to changes in cortisol levels.

A central topic in the cognitive sciences is how cognitive control is adapted flexibly to changing task demands. Conflict monitoring theory originally proposed conflict triggered adjustments of cognitive control after a conflict trial to improve subsequent performance. In the present study, we tested the hypothesis that readjustments of cognitive control occur continuously within a conflict trial itself. Using frequency tagged electroencephalogram in a flanker task, we traced the allocation of attention to target and distracter stimuli. We found evidence for a conflict-triggered within-trial contrast enhancement dissociating target and distracters. This contrast enhancement vanished for consecutive trials with constant tagging frequencies, indicating that trial-to-trial conflict adaptation effects may, at least partly, be the product of interacting processes serving conflict resolution within trials.

Recent research has shown that joint-action effects in a social Simon task provide a good index of action co-representation. The present study aimed to specify the mechanisms underlying joint action by considering trial-to-trial transitions. Using non-social stimuli, we assigned a Simon task to two participants. Each was responsible for only one of two possible responses. This task was performed alone (Individual go/nogo task) and in cooperation with another person who was sitting alongside (Joint go/nogo task). As a further control task, we added a Standard Simon task. Replicating previous findings (Sebanz et al. in Cognition 88:B11-B21, 2003), we found no spatial compatibility effect in the Individual go/nogo task but we did find one in the Joint go/nogo task. A more detailed analysis showed that a sequential modulation of the Simon effect was present in both the Joint and the Individual go/nogo tasks. We found reliable Simon effects in trials following Simon compatible trials not only in the Joint go/nogo task but also to a somewhat smaller extent in the Individual go/nogo task. For both these go/nogo tasks, sequential modulation effects were stronger for nogo/go transitions than for go/go transitions. This suggests that low-level feature binding and repetition mechanisms contribute to the social Simon effect related to the specific requirement not to respond on nogo trials.

The authors investigated the impact of response activation on dual-task performance by presenting a subliminal prime before the stimulus in Task 2 (S2) of a psychological refractory period (PRP) task. Congruence between prime and S2 modulated the reaction times in Task 2 at short stimulus onset asynchrony despite a PRP effect. This Task 2 congruence effect was paralleled by a Task 1 congruence effect and emerged exclusively under conditions of cross talk, whereas it did not occur under dual-task conditions preventing cross talk between tasks. This suggests that response activation operates during the PRP in dual tasks and affects the response times in Task 2 via cross talk between common processing elements at prebottleneck stages but not by directly affecting the postbottleneck stages.