This thesis comprises research investigating explicit EM biases in MDD during acute depression and euthymia (i.e., clinical remission). First, a systematic review was conducted to investigate whether acutely depressed and euthymic MDD participants display an explicit EM bias. An ‘explicit EM bias’ was operationally defined to denote enhanced memory for negative or positive stimuli compared to matched healthy controls (HCs). Studies that were included in this systematic review investigated explicit EM using free recall and recognition memory paradigms. The main finding from this investigation was that acutely depressed MDD participants do not display an explicit EM bias. An unintended consequence of this investigation was the identification that research on explicit EM in MDD during euthymia is surprisingly sparse. Next, building upon the findings from our systematic review, we conducted an empirical investigation of explicit EM within a sample of well-characterized euthymic MDD participants compared to age/sex/gender/IQ-matched HCs. In this study, participants performed incidental encoding (i.e., emotional reactivity) and recognition memory tasks (separated by one week). These tasks employed emotionally-valent picture stimuli obtained from the International Affective Picture System. Results from this study revealed that, compared to matched HCs, euthymic MDD participants do not display an emotional reactivity or explicit EM bias. Taken together, the findings from this thesis suggest that explicit EM represents a sub-domain of cognition that may be unaffected in individuals with MDD. Our findings have important implications for the unified model of depression and may represent a basis upon which future research can build in an attempt to understand the nuanced cognitive phenotypes associated with MDD. / Thesis / Master of Science (MSc) / Major depressive disorder (MDD) is one of the most common mental disorders worldwide. It is estimated that over 10% of Canadians will experience MDD at some point in their lifetime. The symptoms of MDD include, among other things: depressed mood, loss of interest in regular daily activities, and impairments in cognition (e.g., attention, emotion, memory, etc.). Clinicians and researchers have argued for years that MDD is associated with negative cognitive biases, including increased attention to, and more accurate memory for, negative information; however, attention, emotion and memory are general forms of cognition, and the existence of cognitive biases for specific sub-domains of cognition in MDD are largely unknown. Given that MDD has a negative effect on emotion and memory, one potentially important sub-domain of cognition is explicit emotional memory (EM; i.e., conscious memory for emotionally-stimulating information). The purpose of the current thesis was to investigate whether MDD, during both the active (i.e., acute) and euthymic (i.e., clinically-remitted) stages, is associated with explicit EM biases compared to healthy volunteers. This thesis discusses how patterns of explicit EM may be important for our understanding of the development of MDD.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24728 |
| Date | January 2019 |
| Creators | Bogie, Bryce |
| Contributors | Frey, Benicio, Kapczinski, Flávio, Neuroscience |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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