People suffering from chronic worries pay excessive attention to emotional information. In this study we examined whether a reduced ability to inhibit attention from fearful faces (i.e. inhibition of ...return; IOR) can be attributed to the low vagus nerve activity observed in high worriers. Our pre-registered hypothesis was that transcutaneous auricular vagus nerve stimulation (tVNS) would enhance IOR to fearful faces. Ninety-four students who scored above a pre-determined cut-off on the Penn State Worry Questionnaire were randomly allocated to receive either tVNS (n = 45) or sham stimulation of the earlobe (n = 49). Meanwhile, to assess IOR, they performed an emotional exogenous cueing task wherein neutral and fearful faces predicted the target location at chance level. Resting levels of HRV were also collected before stimulation onset. Results showed that levels of trait worry were associated with reduced IOR, but resting levels of HRV were not. Critically, tVNS did not affect performance on the exogenous cueing task when compared to sham stimulation. These findings did not confirm the hypothesized causal role of vagus nerve activity in maintaining disrupted IOR for emotional information. They also provide evidence that high levels of worry are associated with generally reduced IOR. This points to a clear need to understand the neurobiological basis of inhibitory problems in worriers.
•Sham-controlled experiment in selected worriers performing a spatial cueing task.•Tested if stimulating the vagus promotes attentional disengagement to fearful faces.•Transcutaneous stimulation of the vagus nerve did not affect task performance.•Higher levels of worrying were related to prolonged attention to distracting cues.
Transcutaneous auricular vagus nerve stimulation (taVNS) is a neurostimulatory technique hypothesised to enhance central noradrenaline. Currently, there is scarce evidence in support of a ...noradrenergic mechanism of taVNS and limited knowledge on its stimulation parameters (i.e., intensity and pulse width). Therefore, the present study aimed to test whether taVNS enhances pupil dilation, a noradrenergic biomarker, as a function of stimulation parameters. Forty-nine participants received sham (i.e., left ear earlobe) and taVNS (i.e., left ear cymba concha) stimulation in two separate sessions, in a counterbalanced order. We administered short bursts (5s) of seven stimulation settings varying as a function of pulse width and intensity and measured pupil size in parallel. Each stimulation setting was administered sixteen times in separate blocks. We expected short bursts of stimulation to elicit phasic noradrenergic activity as indexed by event-related pupil dilation and event-related temporal derivative. We hypothesised higher stimulation settings, quantified as the total charge per pulse (pulse width x intensity), to drive greater event-related pupil dilation and temporal derivative in the taVNS compared to sham condition. Specifically, we expected stimulation settings in the taVNS condition to be associated with a linear increase in event-related pupil dilation and temporal derivative. We found stimulation settings to linearly increase both pupil measures. In line with our hypothesis, the observed dose-dependent effect was stronger in the taVNS condition. We also found taVNS to elicit more intense and unpleasant sensations than sham stimulation. These results support the hypothesis of a noradrenergic mechanism of taVNS. However, future studies should disentangle whether stimulation elicited sensations mediate the effect of taVNS on evoked pupil dilation.
This study investigated whether transcutaneous auricular vagus nerve stimulation (taVNS) enhances reversal learning and augments noradrenergic biomarkers (i.e., pupil size, cortisol, and salivary ...alpha‐amylase sAA). We also explored the effect of taVNS on respiratory rate and cardiac vagal activity (CVA). Seventy‐one participants received stimulation of either the cymba concha (taVNS) or the earlobe (sham) of the left ear. After learning a series of cue‐outcome associations, the stimulation was applied before and throughout a reversal phase in which cue‐outcome associations were changed for some (reversal), but not for other (distractor) cues. Tonic pupil size, salivary cortisol, sAA, respiratory rate, and CVA were assessed at different time points. Contrary to our hypothesis, taVNS was not associated with an overall improvement in performance on the reversal task. Compared to sham, the taVNS group performed worse for distractor than reversal cues. taVNS did not increase tonic pupil size and sAA. Only post hoc analyses indicated that the cortisol decline was steeper in the sham compared to the taVNS group. Exploratory analyses showed that taVNS decreased respiratory rate but did not affect CVA. The weak and unexpected effects found in this study might relate to the lack of parameters optimization for taVNS and invite to further investigate the effect of taVNS on cortisol and respiratory rate.
Contrary to our hypotheses, we did not observe enhancing effects of transcutaneous auricular vagus nerve stimulation (taVNS) on reversal learning and noradrenergic markers. Our findings question whether a commonly used parameter‐setup of taVNS can activate the vagus nerve and modulate noradrenergic activity. These results add to a growing body of zero findings and call for more basic taVNS research regarding optimal stimulation parameters and locations.
Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neurostimulation technique that is thought to modulate noradrenergic activity. Previous studies have demonstrated ...inconsistent effects of taVNS on noradrenergic activity, which is possibly due to insufficient statistical power, suboptimal stimulation parameter settings, and data collection procedures. In this preregistered within-subject experiment, 44 healthy participants received taVNS and sham (earlobe) stimulation during two separate experimental sessions. Stimulation intensity was individually calibrated to the maximum level below pain. During each session, participants received the stimulation continuously ten minutes before an auditory novelty oddball task till the end of the experimental session. The P3b component of the event-related potential served as a marker of phasic noradrenergic activity, whereas P3a magnitude was explored as an index of dopaminergic activity. Salivary alpha-amylase (sAA) was measured as an index of tonic noradrenergic activity before and at the end of the stimulation. The taVNS and sham conditions did not differ in P3a or P3b magnitudes, nor sAA secretion. These findings call into question whether taVNS, administered continuously at high, nonpainful stimulation intensities, reliably augments noradrenergic activity via the vagus nerve.
•Evidence for a noradrenergic mechanism of taVNS is mixed.•Shortcomings of previous studies might underlie such inconsistent evidence.•We tested if continuous taVNS at the maximum intensity increases P3b and sAA.•taVNS did not increase either noradrenergic marker.
Although transcutaneous auricular vagus nerve stimulation (taVNS) is thought to increase central noradrenergic activity, findings supporting such mechanism are scarce and inconsistent. This study ...aimed to investigate whether taVNS modulates indirect markers of phasic and tonic noradrenergic activity. Sixty‐six healthy participants performed a novelty auditory oddball task twice on separate days: once while receiving taVNS (left cymba concha), once during sham (left earlobe) stimulation. To maximize potential effects, the stimulation was delivered continuously (frequency: 25 Hz; width: 250 μs) at an intensity individually calibrated to the maximal level below pain threshold. The stimulation was administered 10 min before the oddball task and maintained throughout the session. Event‐related pupil dilation (ERPD) to target stimuli and pre‐stimulus baseline pupil size were assessed during the oddball task as markers of phasic and tonic noradrenergic activity, respectively. Prior to and at the end of stimulation, tonic pupil size at rest, cortisol, and salivary alpha‐amylase were assessed as markers of tonic noradrenergic activity. Finally, we explored the effect of taVNS on cardiac vagal activity, respiratory rate, and salivary flow rate. Results showed a greater ERPD to both target and novelty compared to standard stimuli in the oddball task. In contrast to our hypotheses, taVNS did not impact any of the tested markers. Our findings strongly suggest that continuous stimulation of the cymba concha with the tested stimulation parameters is ineffective to increase noradrenergic activity via a vagal pathway.
There is inconsistent evidence supporting a noradrenergic mechanism of transcutaneous auricular vagus nerve stimulation (taVNS). This statistically well‐powered study aimed to further test whether taVNS at the cymba concha modulates markers of tonic and phasic noradrenergic activity (pupil‐related indices, cortisol, salivary alpha‐amylase). The zero‐findings of this study question whether continuous taVNS with a set of commonly used stimulation parameters (25 Hz, 250 μs, individually tailored intensity below pain) modulates noradrenergic activity via a vagal pathway.
•First study to assess effects of tVNS on fear conditioning in humans.•tVNS accelerates explicit fear extinction.•tVNS did not affect retention or reinstatement 24-h later.
A critical component of ...the treatment for anxiety disorders is the extinction of fear via repeated exposure to the feared stimulus. This process is strongly dependent on successful memory formation and consolidation. Stimulation of the vagus nerve enhances memory formation in both animals and humans. The objective of this study was to assess whether transcutaneous stimulation of the vagus nerve (tVNS) can accelerate extinction memory formation and retention in fear conditioned humans. To assess fear conditioning and subsequent fear extinction, we assessed US expectancy ratings, fear potentiated startle responses and phasic heart rate responses. We conducted a randomized controlled trial in thirty-one healthy participants. After fear conditioning participants were randomly assigned to receive tVNS or sham stimulation during the extinction phase. Retention of extinction memory was tested 24h later. tVNS accelerated explicit fear extinction learning (US expectancy ratings), but did not lead to better retention of extinction memory 24h later. We did not find a differential physiological conditioning response during the acquisition of fear and thus were unable to assess potential effects of tVNS on the extinction of physiological indices of fear. These findings complement recent studies that suggest vagus nerve stimulation could be a promising tool to improve memory consolidation and fear extinction.
Digital quantum computers have the potential to simulate complex quantum systems. The spin-boson model is one of such systems, used in disparate physical domains. Importantly, in a number of setups, ...the spin-boson model is open, i.e., the system is in contact with an external environment which can, for instance, cause the decay of the spin state. Here, we study how to simulate such open quantum dynamics in a digital quantum computer, for which we use an IBM hardware. We consider in particular how accurate different implementations of the evolution result as a function of the level of noise in the hardware and of the parameters of the open dynamics. For the regimes studied, we show that the key aspect is to simulate the unitary portion of the dynamics, while the dissipative part can lead to a more noise-resistant simulation. We consider both a single spin coupled to a harmonic oscillator, and also two spins coupled to the oscillator. In the latter case, we show that it is possible to simulate the emergence of correlations between the spins via the oscillator.
Non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) has received tremendous attention as a potential neuromodulator of cognitive and affective functions, which likely exerts its ...effects via activation of the locus coeruleus-noradrenaline (LC-NA) system. Reliable effects of taVNS on markers of LC-NA system activity, however, have not been demonstrated yet.
The aim of the present study was to overcome previous limitations by pooling raw data from a large sample of ten taVNS studies (371 healthy participants) that collected salivary alpha-amylase (sAA) as a potential marker of central NA release.
While a meta-analytic approach using summary statistics did not yield any significant effects, linear mixed model analyses showed that afferent stimulation of the vagus nerve via taVNS increased sAA levels compared to sham stimulation (b = 0.16, SE = 0.05, p = 0.001). When considering potential confounders of sAA, we further replicated previous findings on the diurnal trajectory of sAA activity.
Vagal activation via taVNS increases sAA release compared to sham stimulation, which likely substantiates the assumption that taVNS triggers NA release. Moreover, our results highlight the benefits of data pooling and data sharing in order to allow stronger conclusions in research.
•Data pooling across 10 studies showed that taVNS leads to increased salivary alpha-amylase release compared to sham.•These findings substantiate the assumption that vagal activation via taVNS triggers noradrenaline release.•The diurnal trajectory of salivary alpha-amylase activity was replicated.
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