Background: rumination is both a symptom and predictor of major depressive disorder (MDD). In MDD patients, rumination is correlated with depression severity, and for healthy people rumination is a...Show moreBackground: rumination is both a symptom and predictor of major depressive disorder (MDD). In MDD patients, rumination is correlated with depression severity, and for healthy people rumination is a predictor of the onset and duration of a depressive episode. Recently, rumination was shown to be correlated to functional connectivity in the default mode network (DMN) in the brain. During working memory (WM) tasks, the central executive network (CEN) shows high connectivity and the DMN shows low connectivity, whereas during rest this is the other way around. This ‘switching’ between DMN and CEN connectivity is blunted in MDD patients, but it is still unknown whether this ‘switch’ is affected by acute rumination in healthy participants. The aim of the current study is to determine the effect of acute rumination on the switching between the DMN and the CEN in healthy participants. Methods: 36 healthy females, randomly assigned to the acute-rumination group (n=18) or the no-rumination group (n=18) underwent fMRI assessment during a rest-WM task (alternating rest and WM conditions). Only for the acute-rumination group, an acute rumination phase immediately preceded the rest-WM task. Pearson’s correlation was performed to analyze the correlation between the DMN and the CEN in each participant. A mixed ANOVA was performed to analyze the effects of acute rumination. Results: Negative Pearson correlation coefficients were found between DMN and CEN for both groups. A statistically significant interaction effect was found for network (CEN versus DMN) × condition (rest versus WM). However, no statistically significant main effect was found for group (acute-rumination versus no-rumination). Conclusion: Consistent with previous studies an interaction in the expected direction was found between the DMN and CEN. However, this study does not support the effect of acute rumination on this interaction. The current study contributes to an increased understanding of the effect of rumination, and contributes to research of this prominent symptom of MDD and other psychological disorders.Show less
Research master thesis | Psychology (research) (MSc)
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Introduction: The default mode network (DMN) is a large intrinsic network in the brain, which seems to be affected in depressed patients. Also, aberrant heart rate variability (HRV) is often found...Show moreIntroduction: The default mode network (DMN) is a large intrinsic network in the brain, which seems to be affected in depressed patients. Also, aberrant heart rate variability (HRV) is often found in this population. Ketamine is thought to be a fast-acting antidepressant and has shown to have an effect on HRV and intrinsic brain connectivity. In this study, the effect of HRV on resting-state functional connectivity of the DMN and brain activity of areas within the DMN that were significantly correlated with HRV was examined. Also, it was investigated whether ketamine moderated this relationship. Method: Twelve healthy men received an intravenous ketamine or placebo infusion on two occasions. Resting-state functional connectivity and HRV were measured before, during, and after infusion. Dual-regression was used to obtain DMN connectivity scores, while a whole brain analysis was done to determine which brain areas were correlated with HRV. Raw digitized electrocardiogram (EKG), obtained with a pulse oximeter, was analyzed in order to extract HRV data. Multilevel analysis was used to determine the effect of HRV and ketamine on resting-state functional connectivity in the DMN and brain activity in the subgenual anterior cingulate cortex (sgACC), right dorsolateral prefrontal cortex (dlPFC), and the left postcentral gyrus. Results: DMN connectivity strength was negatively related to HRV, but positively related to activity of the right dlPFC and the left postcentral gyrus for the placebo condition. Ketamine was associated with a more profound effect of HRV on DMN connectivity and brain activity within the postcentral gyrus. Discussion: The present results complement recent studies that show that HRV is associated with connectivity strength in the DMN. Implications for the relevance of using ketamine in depressed patients are discussed. Initial increases of DMN connectivity are followed by a decrease in the DMN, which may be beneficial for depressed patients who generally show hyperconnectivity within the DMN. Results thus imply that ketamine has a moderating role in this.Show less
