Research master thesis | Psychology (research) (MSc)
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Atomoxetine is a prescription drug often used to restore executive (or cognitive) functioning in patients with attention-deficit/hyperactivity disorder and other neuropsychiatric conditions....Show moreAtomoxetine is a prescription drug often used to restore executive (or cognitive) functioning in patients with attention-deficit/hyperactivity disorder and other neuropsychiatric conditions. Moreover, this drug may potentially be ingested by healthy individuals who seek to improve their cognitive performance. However, the effect of atomoxetine on healthy brain functioning remains largely unclear. Network approaches have become useful for studying how the functional connectivity between brain regions may enhance or hinder executive functioning. Accordingly, to further examine the underlying mechanisms of action of atomoxetine, it is relevant to explore how this drug influences the functional connectivity of a large-scale brain network involved in the control of top-down processes: the executive control network (ECN). The aim of this study was thus to investigate the effect of atomoxetine (40 mg) on the functional connectivity of the ECN in healthy volunteers (n = 15). Network analyses were conducted on unpublished functional magnetic resonance (fMRI)-data collected by Chamberlain and colleagues (2009) in a double-blind, placebo-controlled, within-subjects, crossover design in which participants completed a goal-directed fMRI-task (i.e., the temporal discounting task), probing the ECN. Contrary to expectations, a paired-samples permutation test, corrected for multiple comparisons by means of a threshold free cluster enhancement, revealed that the functional connectivity of the participants’ ECN does not increase significantly after ingesting atomoxetine as compared to placebo (p > .05 corrected). Nevertheless, exploratory analyses indicated that, relative to placebo, atomoxetine significantly strengthens the functional connectivity of a frontoparietal network highly associated with cognition and language paradigms (t(14) = 7.61, p = .003). Together, these results suggest that, in healthy individuals, atomoxetine might not have enhancing effects on the processes supported by the ECN but (potentially) on those supported by a frontoparietal network. Atomoxetine might thus have beneficial effects in the cognitive performance of healthy individuals by facilitating certain processes associated with both cognition and language. Further research is however warranted to corroborate these findings in confirmatory studies and enhance the understanding of the underlying mechanisms of action of atomoxetine in healthy brain functioning.Show less
Background. Anxiety disorders are considered to be the most common psychiatric disorder. Knowing underlying mechanisms can help to improve treatment effectiveness. Thus, the study researches the...Show moreBackground. Anxiety disorders are considered to be the most common psychiatric disorder. Knowing underlying mechanisms can help to improve treatment effectiveness. Thus, the study researches the association of anxiety, rumination, heart rate variability (HRV) and the Default Mode Network (DMN). Previous studies indicate a relationship between the factors. The DMN has been found to be essential for self-related cognitive activity. Its functional connectivity (FC) has been shown to be impaired in major psychiatric disorders. Research Question. The study investigates described associations within a population of high trait ruminators, rumination being experimentally manipulated. It is hypothesized that an increase in rumination is associated with lower HRV. High anxiety levels are expected to be related to lower HRV. The FC within the DMN is expected to be affected by rumination. The resulting DMN effect size is predicted to be associated with HRV and anxiety. Methods. A cross-sectional, within-subject experimental design was implemented. The sample consists of 33 female healthy participants who filled out the Penn State Worry Questionnaire and Ruminative Responses Scale. The FC within the DMN was assessed carrying out a working memory task and being cued with memories inducing rumination. Results. Solely a significant positive correlation has been found between anxiety and rumination. Brain areas of the DMN showed an increase in FC during rumination induction compared to rest condition. This effect was significantly negatively related to HRV. Conclusion. The significant relationship between rumination and anxiety should be considered in mental healthcare institutions. The FC of the DMN needs further research to derive practical value.Show less
Worry and anxiety are associated with an increase in absolute heart rate, while heart rate variability decreases. Low heart rate variability is associated with an active anterior insula. A...Show moreWorry and anxiety are associated with an increase in absolute heart rate, while heart rate variability decreases. Low heart rate variability is associated with an active anterior insula. A hyperactive anterior insula is observed in individuals with anxiety disorders. However, it is not yet known whether a hyperactive anterior insula makes a person vulnerable to developing anxiety disorders or whether the anterior insula becomes hyperactive as a result of the disorder. Therefore, this study aims to investigate these associations in healthy participants. The following research questions were asked, "Is there a correlation between absolute heart rate and trait worry?" and "Is trait worry associated with low heart rate variability?" the same questions are posed in the context of anxiety. Finally, the question "Is trait anxiety associated with a hyperactive insula?" is asked. To examine this, data from the HADS, PSWQ, vectorcardiogram measures of heart rate and the heart rate variability, and the functional connectivity of the salience network from the 30 female participants were used. Results show no significant relationship between absolute heart rate, heart rate variability, and trait worry and anxiety in healthy participants. A significant relationship between the functional connectivity in the anterior insula and trait anxiety was found in our sample (r = .42, p = <.05). The effects of worry and anxiety on cardiac activity are mainly seen in clinically diagnosed individuals under an unpredictable and uncontrollable stressful environment. Our sample were healthy individuals, so symptoms were apparently not severe enough. The effects of trait anxiety are directly reflected in brain connectivity in the anterior insula observed in our analysis. The results can be applied to treatments reducing anxiety and worry.Show less
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
Major depressive disorder (MDD) has been linked to aberrant functional connectivity in large scale neural networks, such as reduced salience network (SN) functional connectivity, as well as...Show moreMajor depressive disorder (MDD) has been linked to aberrant functional connectivity in large scale neural networks, such as reduced salience network (SN) functional connectivity, as well as decreased resting heart rate variability (HRV). It is unknown whether these features are present in depressed patients, as a consequence of MDD, or also present in healthy individuals at risk for depression, which would indicate their playing a broader role in the development of MDD. The current study aimed to investigate this in a healthy sample at risk for depression, using a cross-sectional, between-subject experimental design. To select a healthy sample at risk, individuals were screened for having a general tendency to ruminate. The intention was to include individuals with high scores on rumination’s facet of brooding, which is a pertinent risk factor for depression. Nevertheless, this screening was unsuccessful in selecting a sample at risk, since analyses revealed healthy levels of brooding. However, the present sample (N = 29) did display reduced HRV and elevated cognitive reactivity to sadness. Against prediction, no significant negative relationship was found between SN connectivity and brooding trait scores. As expected, SN connectivity was positively linked to HRV. Exploratory correlational analyses revealed connectivity within the right anterior insula to be positively linked to HRV. Given the healthy levels of brooding, no inferences can be made regarding this risk factor for depression development. Nonetheless, the results replicate the coupling of SN and HRV in a healthy sample, thereby providing further evidence of the SN’s role in autonomic modulation.Show less
BACKGROUND: Cortical correlates to heart rate variability (HRV) are assumed to involve interconnectivity between single brain areas and large-scale brain networks (LSN) in the extended...Show moreBACKGROUND: Cortical correlates to heart rate variability (HRV) are assumed to involve interconnectivity between single brain areas and large-scale brain networks (LSN) in the extended neurovascular integration model (NVI). Among those are the CEN and the DMN from the triple network model (TNM) and the anterior insula (AI) and the dorsal anterior cingulate cortex (DACC). This study aimed to test if AI and DACC are involved as the SN in FC patterns that correlate to HRV. Second, it was tested if LSN show FC patterns in accordance with the TNM during experimental tasks. METHODS: 27 female participants (18- 35 years) took part in this cross-sectional fMRI study. Experimentally induced FC patterns of the three LSN with HRV as a covariate were used for the statistical model. RESULTS: As hypothesised, the CEN showed significantly more intrinsic FC during the WMT which was associated with HRV. Further, there was an association between HRV and the FC between the CEN and AI/ACC, respectively. Against the hypothesis, an involvement of the full SN could not be confirmed. The results concerning the DMN disconfirm the hypothesis of an increased FC during the rumination condition. Lastly, a trend was visible for lower HRV during the WMT compared to the rumination condition, but this difference did not reach the significance level. CONCLUSION: The present results confirm the AI and ACC as autonomous brain regions involved in FC patterns associated with HRV. This confirmation of the NVI opposes the unexpectedly high FC pattern of the DMN during the WMT, which points to explanatory gaps in the external validity of the model and the role of LSN vs. single brain regions as associates of HRV.Show less
Recent research has only shown little evidence for a relationship between patient characteristics and treatment outcome. It is proposed that patients with a higher need of Mental Health Care due to...Show moreRecent research has only shown little evidence for a relationship between patient characteristics and treatment outcome. It is proposed that patients with a higher need of Mental Health Care due to higher psychopathologic complexity receive more treatment compared to others to reach a comparatively good treatment result. The treatment dose in more complex patients might therefore be significantly higher than in less complex patients. According to that, treatment dose should mediate the relationship between complexity and outcome. Thereby, the main purpose of this study is the investigation of a proposed mediation effect by treatment dose, operationalized as treatment duration in minutes and treatment length in days. Clinical Complexity was based on the degree of psychopathological severity and treatment outcome was measured with the self-report questionnaire Outcome Questionnaire-45. This investigation is based on a sample of patients in ambulatory treatment, who suffer from anxiety disorders, originated from the GGZ institution Arkin, an MHC provider in the Netherlands. Finally, no mediation effect has been shown and no evidence for an existent triadic relationship between complexity, outcome and treatment dose has been found. Besides, treatment duration correlated positively with complexity. Patients with higher complexity also tend to have a less favorable treatment outcome compared with patients of lower complexity. The results of this study should be interpreted and dealt with caution due to potential threats to internal and external validity. In future research alternative complexity and treatment dose indicators need further investigation to assess the prognostic value of patient characteristics for treatment outcome.Show less
Research master thesis | Psychology (research) (MSc)
closed access
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
