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Title: The role of self-blame in major depressive disorder and its impact on social-economical decision making : evidence from neuroimaging and neuroeconomical experiments
Author: Pulcu, Erdem
ISNI:       0000 0004 5364 0300
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2014
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This Ph.D. investigates behavioural and neuroimaging correlates of affective disturbances related to self blaming moral emotions in major depressive disorder (MDD), and their impact on social economical decision making. Guilt is one of the core symptoms of MDD, and there is growing evidence of abnormally elevated shame in MDD especially when patients are symptomatic. In the introduction, behavioural and neuroimaging studies of emotional impairments in MDD and their influence on social economical decision making are reviewed. The third chapter investigated temporal discounting behaviour in current and remitted patients with MDD compared with healthy participants. Temporal discounting relates to the extent to which people consider making financial investments into the future and therefore is an important dimension of social economical decision making and reward valuation over time which is likely to influence people's behavioural preferences. We showed that discounting coefficients for large sized rewards are significantly higher in current MDD and correlate significantly with depressive symptoms, particularly hopelessness about the future. The fourth chapter considers altruism in MDD, as investigated by four different neuroeconomical paradigms relating to different forms of altruistic behaviours. Previous publications theoretically associated MDD with guilt driven pathological hyper altruism. However, behavioural-economical evidence to support this hypothesis is lacking. Using neuroeconomical paradigms, we investigated whether elevated levels of altruistic forms of guilt translate into altruistic behaviour in current and remitted MDD. Furthermore, we investigated whether elevated self blaming feelings may be triggered by receiving unfair offers in the Ultimatum Game. We showed that patients with current MDD made fewer charitable donations, and secondly we showed that elevated levels of guilt may be important for understanding the lack of altruistic punishment behaviour. Taken together, we suggested that the hyper altruism hypothesis should be revised, particularly to exclude altruistic punishment behaviour. Across these different experiments a pattern has emerged showing that patients with remitted MDD behaved significantly more altruistically. This raised the question whether patients with remitted MDD are experiencing altruistic behaviours more socially rewarding. In the next paper/chapter, we aimed to address this issue by using an adapted version of the charitable donations experiment with functional imaging. We showed that there is an abnormal hyperactivation in subgenual cingulate cortex and right striatum for altruistic decisions. The final research paper investigated whether shame relative to guilt has distinct functional neuroanatomy in patients fully remitted from symptoms. Chapter 6 shows that shame is associated with increased response of the right amygdala and the right posterior insula in patients with remitted MDD. We argued that these abnormal activations may be a biomarker of depression vulnerability. In the discussion section, we evaluated the findings of our experiments and discussed their implications from an interdisciplinary perspective, raising new research questions for the future directions of understanding social decision-making in major depression.
Supervisor: Elliott, Rebecca; Zahn, Roland Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available