Vagally-mediated HRV as a marker of trait rumination in healthy individuals? A large cross-sectional analysis.

The tendency to ruminate (i.e., repetitive, self-referential, negative thoughts) is a maladaptive form of emotional regulation and represents a transdiagnostic vulnerability factor for stress-related psychopathology. Vagally-mediated heart rate variability (vmHRV) provides a non-invasive, surrogate measure of vagal modulation of the heart, and higher HRV is considered an indicator of susceptibility, or ability to respond to stress. Past research has suggested a link between trait rumination and vmHRV; however, inconsistent results exist in healthy individuals. In this study, we investigated the association between the tendency to ruminate, brooding, and reflection (using the Ruminative Response Scale) with vmHRV measured at baseline in a healthy population using a large cross-sectional dataset (N = 1189, 88% female; mean age = 21.55, ranging from 17 to 48 years old), which was obtained by combining samples of healthy individuals from different studies from our laboratory. The results showed no cross-sectional correlation between vmHRV and trait rumination (confirmed by Bayesian analysis), even after controlling for important confounders such as gender, age, and depressive symptoms. Also, a non-linear relationship was rejected. In summary, based on our results in a large sample of healthy individuals, vmHRV is not a marker of trait rumination (as measured by the Ruminative Response Scale).

The effects of left dorsolateral prefrontal transcranial direct current stimulation on episodic future thinking following acute psychosocial stress.

INTRODUCTION: Research on stress-related disorders and brain imaging suggests that (acute) stress might impact the capacity to mentally simulate specific episodic future events (EFT) through the effects of cortisol on brain regions supporting this cognitive function, such as the prefrontal cortices. This study aims to examine the mechanisms underlying this link, using transcranial Direct Current Stimulation (tDCS) over the left dorsolateral prefrontal cortex. METHODS: 60 healthy participants were subjected to the Montreal Imaging Stress Task (MIST), followed by either active or sham tDCS. After stimulation, the EFT task was administered. Salivary cortisol was measured throughout the protocol. RESULTS: Higher cortisol AUCi values were linked to less specific episodic future thoughts. Moreover, active tDCS enhanced EFT specificity irrespective of cortisol, especially in high trait ruminators. We did not observe an effect from active tDCS on cortisol AUCi, and equally there was no interaction effect between cortisol AUCi and stimulation condition predictive for EFT specificity. CONCLUSION: Although we did not find evidence for the effects of tDCS on the HPA-system, our data reveal a crucial link between two critical predictors of mental health for the first time, and provide a solution to help rehabilitate EFT deficits.Trial registration: Netherlands National Trial Register identifier: ntr004..

Individual resting-state frontocingular functional connectivity predicts the intermittent theta burst stimulation response to stress in healthy female volunteers.

Intermittent theta burst stimulation (iTBS) delivered to the dorsolateral prefrontal cortex (DLPFC) has been investigated as a promising treatment for stress and stress-related mental disorders such as major depression, yet large individual differences in responsiveness demand further exploration and optimization of its effectiveness. Clinical research suggests that resting-state functional connectivity (rsFC) between the DLPFC and the anterior cingulate cortex (ACC) can predict iTBS treatment response in depression. The present study aimed to investigate whether rsFC between the left DLPFC and ACC subregions could predict the degree to which the stress system is affected by iTBS. After assessment of baseline resting-state fMRI data, 34 healthy female participants performed the Trier Social Stress Test on two separate days, each followed by active or sham iTBS over the left DLPFC. To evaluate iTBS effects on the stress-system, salivary cortisol was measured throughout the procedure. Our results showed that a stronger negative correlation between the left DLPFC and the caudal ACC was linked to a larger attenuation of stress-system sensitivity during active, but not during sham iTBS. In conclusion, based on individual rsFC between left DLPFC and caudal ACC, iTBS could be optimized to more effectively attenuate deregulation of the stress system.

Beyond time and space: The effect of a lateralized sustained attention task and brain stimulation on spatial and selective attention.

The Theory of Visual Attention (TVA) provides a mathematical formalisation of the "biased competition" account of visual attention. Applying this model to individual performance in a free recall task allows the estimation of 5 independent attentional parameters: visual short-term memory (VSTM) capacity, speed of information processing, perceptual threshold of visual detection; attentional weights representing spatial distribution of attention (spatial bias), and the top-down selectivity index. While the TVA focuses on selection in space, complementary accounts of attention describe how attention is maintained over time, and how temporal processes interact with selection. A growing body of evidence indicates that different facets of attention interact and share common neural substrates. The aim of the current study was to modulate a spatial attentional bias via transfer effects, based on a mechanistic understanding of the interplay between spatial, selective and temporal aspects of attention. Specifically, we examined here: (i) whether a single administration of a lateralized sustained attention task could prime spatial orienting and lead to transferable changes in attentional weights (assigned to the left vs right hemi-field) and/or other attentional parameters assessed within the framework of TVA (Experiment 1); (ii) whether the effects of such spatial-priming on TVA parameters could be further enhanced by bi-parietal high frequency transcranial random noise stimulation (tRNS) (Experiment 2). Our results demonstrate that spatial attentional bias, as assessed within the TVA framework, was primed by sustaining attention towards the right hemi-field, but this spatial-priming effect did not occur when sustaining attention towards the left. Furthermore, we show that bi-parietal high-frequency tRNS combined with the rightward spatial-priming resulted in an increased attentional selectivity. To conclude, we present a novel, theory-driven method for attentional modulation providing important insights into how the spatial and temporal processes in attention interact with attentional selection.