The effect of neurostimulation applied to the left dorsolateral prefrontal cortex on post-stress adaptation as a function of depressive brooding.

Depressive brooding following a stressful event predicts negative affect and neuroendocrine responses related to psychological stress. The dorsolateral prefrontal cortex (DLPFC) has been associated with the top-down regulation of thoughts and emotions, and abnormal neural activity within this region has been associated with increased psychological stress and ruminative thinking. The aim of this study was to investigate whether the modulation of the DLPFC could have beneficial effects on ruminative thoughts and the endocrine response following a self-relevant stressor. Using a sham-controlled within-subjects crossover-design, two sessions of intermittent theta-burst stimulation (iTBS) were administered over the left DLPFC to thirty-eight healthy-volunteers after they were confronted with a social-evaluative stressor, the Trier Social Stress Test. To assess stress recovery, momentary rumination was measured before and after a resting period subsequent to the encounter with the stressor. In addition, cortisol levels were measured between and after the two iTBS sessions that were applied during the stress recovery phase. Overall, iTBS did not significantly influence ruminative thinking and cortisol secretion during the stress recovery phase. However, taking into account participants ruminative tendencies, our results revealed that for participants with higher levels of brooding ruminative thinking remained stable after iTBS, whereas in the sham condition there was a marginal significant increase in ruminative thinking. Moreover, only after iTBS, there was a significant reduction in cortisol secretion (i.e. a faster return to baseline as compared to sham) for high brooders during the recovery from the stressor. These results show that the prefrontal cortex plays a role in stress recovery mechanisms in individuals who are more vulnerable for psychopathology.

Helping Your Partner with Chronic Pain: The Importance of Helping Motivation, Received Social Support, and Its Timeliness.

Objective: Like all intentional acts, social support provision varies with respect to its underlying motives. Greater autonomous or volitional motives (e.g., enjoyment, full commitment) to help individuals with chronic pain (ICPs) are associated with greater well-being benefits for the latter, as indexed by improved satisfaction of their psychological needs for autonomy, competence, and relatedness. The present study investigates the processes explaining why partners' autonomous or volitional helping motivation yields these benefits. Methods: A total of 134 couples, where at least one partner had chronic pain, completed a 14-day diary. Partners reported on their daily helping motives, whereas ICPs reported on their daily received support, timing of help, need-based experiences, and pain. Results: On days when partners provided help for volitional motives, ICPs indicated receiving more help, which partially accounted for the effect of autonomous helping motivation on ICP need-based experiences. Timing of help moderated the effects of daily received support on ICP need-based experiences. Conclusions: Findings highlight the importance of ICPs of receiving support in general and the role of timing in particular, which especially matters when there is little support being received.

More Precise Estimation of Lower-Level Interaction Effects in Multilevel Models.

In hierarchical data, the effect of a lower-level predictor on a lower-level outcome may often be confounded by an (un)measured upper-level factor. When such confounding is left unaddressed, the effect of the lower-level predictor is estimated with bias. Separating this effect into a within- and between-component removes such bias in a linear random intercept model under a specific set of assumptions for the confounder. When the effect of the lower-level predictor is additionally moderated by another lower-level predictor, an interaction between both lower-level predictors is included into the model. To address unmeasured upper-level confounding, this interaction term ought to be decomposed into a within- and between-component as well. This can be achieved by first multiplying both predictors and centering that product term next, or vice versa. We show that while both approaches, on average, yield the same estimates of the interaction effect in linear models, the former decomposition is much more precise and robust against misspecification of the effects of cross-level and upper-level terms, compared to the latter.

Anodal tDCS over the right dorsolateral prefrontal cortex modulates cognitive processing of emotional information as a function of trait rumination in healthy volunteers.

Healthy individuals reporting higher (as compared to lower) levels of trait rumination recruit more neural activity in dorso-cortical regions (mostly in the right hemisphere) when inhibiting negative information, possibly to compensate their difficulty to disengage from it. In the present study, we investigated whether these latter neural correlates are causally implicated in cognitive control in these individuals. We administered the Cued Emotional Control Task, a measure of cognitive control indexed by cognitive costs for inhibiting versus providing a habitual response for emotional information, in thirty-five healthy volunteers reporting a broad range of trait rumination levels. Participants completed the task after receiving both real and sham-placebo (counterbalanced order) anodal transcranial Direct Current Stimulation (tDCS) over the right dorsolateral prefrontal cortex (DLPFC). Results reveal that the tDCS induced effects on cognitive costs for emotional information were associated with individual differences in trait rumination: the higher the trait rumination level, the less cognitive costs following real neuromodulation of the right DLPFC. Interestingly, these effects were observed for both positive and negative stimuli, and not only negative information as hypothesized. Overall, the data suggest that the right DLPFC is causally involved in the alteration of cognitive control in healthy individuals who tend to ruminate, possibly by helping them to disengage from emotional material.

Within-Subject Mediation Analysis in AB/BA Crossover Designs.

Crossover trials are widely used to assess the effect of a reversible exposure on an outcome of interest. To gain further insight into the underlying mechanisms of this effect, researchers may be interested in exploring whether or not it runs through a specific intermediate variable: the mediator. Mediation analysis in crossover designs has received scant attention so far and is mostly confined to the traditional Baron and Kenny approach. We aim to tackle mediation analysis within the counterfactual framework and elucidate the assumptions under which the direct and indirect effects can be identified in AB/BA crossover studies. Notably, we show that both effects are identifiable in certain statistical models, even in the presence of unmeasured time-independent (or upper-level) confounding of the mediator-outcome relation. Employing the mediation formula, we derive expressions for the direct and indirect effects in within-subject designs for continuous outcomes that lend themselves to linear modelling, under a large variety of settings. We discuss an estimation approach based on regressing differences in outcomes on differences in mediators and show how to allow for period effects as well as different types of moderation. The performance of this approach is compared to other existing methods through simulations and is illustrated with data from a neurobehavioural study. Lastly, we demonstrate how a sensitivity analysis can be performed that is able to assess the robustness of both the direct and indirect effect against violation of the "no unmeasured lower-level mediator-outcome confounding" assumption.

Preschool predictors of mathematics in first grade children with autism spectrum disorder.

Up till now, research evidence on the mathematical abilities of children with autism spectrum disorder (ASD) has been scarce and provided mixed results. The current study examined the predictive value of five early numerical competencies for four domains of mathematics in first grade. Thirty-three high-functioning children with ASD were followed up from preschool to first grade and compared with 54 typically developing children, as well as with normed samples in first grade. Five early numerical competencies were tested in preschool (5-6 years): verbal subitizing, counting, magnitude comparison, estimation, and arithmetic operations. Four domains of mathematics were used as outcome variables in first grade (6-7 years): procedural calculation, number fact retrieval, word/language problems, and time-related competences. Children with ASD showed similar early numerical competencies at preschool age as typically developing children. Moreover, they scored average on number fact retrieval and time-related competences and higher on procedural calculation and word/language problems compared to the normed population in first grade. When predicting first grade mathematics performance in children with ASD, both verbal subitizing and counting seemed to be important to evaluate at preschool age. Verbal subitizing had a higher predictive value in children with ASD than in typically developing children. Whereas verbal subitizing was predictive for procedural calculation, number fact retrieval, and word/language problems, counting was predictive for procedural calculation and, to a lesser extent, number fact retrieval. Implications and directions for future research are discussed.