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  • Affective memory biases a key element

    2018-11-07

    Affective memory biases, a key element of the cognitive (Disner et al., 2011) and neuropsychological models of MDD (Roiser and Sahakian, 2013), are a common finding (Dalgleish and Werner-Seidler, 2014; Bradley and Mathews, 1988). Dalgleish and Werner-Seidler (2014) highlight the key components of the dysfunction of memory processes seen in depression including biases towards the retrieval of negative material specifically during the recollection of negative personal memories or the false generation of these memories. Recall of positive memories is conversely biased with poor access to these memories or an inability to derive emotional benefit from positive recollections. In a word recall task adult MDD patients remember more negative than positive words, while control participants show the inverse pattern (Bradley and Mathews, 1988). Functional neuroimaging of emotional memory tasks reveals dysfunction in various bmn 673 regions. During encoding of positive words, adult MDD patients have altered activity in anterior cingulate (ACC), PFC, HC and AMG, while during negative encoding there is altered activity in the AMG, ACC and insula (Hamilton and Gotlib, 2008; Arnold et al., 2011; van Tol et al., 2012). These regions of dysfunction are aligned with recent meta-analytic evidence of neural dysfunction in MDD across a range of functional MRI paradigms (Graham et al., 2013), demonstrating that affective memory tasks provide a useful probe for the neural dysfunction observed more broadly in MDD. There is evidence from juvenile samples that similar biases in memory processing may also be associated with depression in children under 12 years (Jacobs et al., 2008; Bishop et al., 2004; Drummond et al., 2006; Rudolph et al., 1997), and in an adolescent MDD group such biases show a relationship with age, with greater biases for negative information shown in older individuals (Neshat-Doost et al., 1998). In that study a positive correlation between self-reported severity of depression and recall performance also was identified. Changes in affective memory biases with age could have important implications for the presentation of MDD at different ages and the subsequent treatment of the condition. These biases are also present in adolescents with high emotionality (a risk factor for MDD) in the absence of current or past mental illness, suggesting a cognitive bias vulnerability may antedate the emergence of MDD per se (Kelvin et al., 1999; Roiser and Sahakian, 2013). Improving our understanding of the neural substrate of MDD during adolescence, in its emergence, may also shed light on cognitive and neural mechanisms of the disorder that become evident in adult patient populations. Studies in adolescent MDD support dysfunction in frontal, limbic and occipital areas, in accordance with the adult literature (Halari et al., 2009; Roberson-Nay et al., 2006; Tao et al., 2012; Yang et al., 2009, 2010). Roberson-Nay et al. (2006) report reduced memory for faces and differential activation in the amygdala and anterior hippocampus during memory encoding in adolescents with MDD. Recent reviews also highlight the key areas of functional difference in adolescent MDD, and demonstrate the importance of cortical-limbic deficits shown by lower connectivity in networks associated with emotional dysregulation (Hulvershorn et al., 2012). Furthermore, functional alterations in the ventromedial frontal regions, orbito-frontal and anterior cingulate cortices and subcortical regions including the amygdala and striatum in depressed children appear in both task and non-task (i.e., resting state) acquisitions (Kerestes et al., 2014). In Cloning vector study we examine behavioural performance and functional activation on a self-referential word-based memory task in a large sample of adolescents with MDD and healthy controls. Firstly, we consider the behavioural performance for encoding and recognition in adolescents with MDD and controls, considering four outcome measures: categorisation accuracy; categorisation reaction time; memory sensitivity (d′); and recognition reaction time. Secondly, considering the neural response to this task we examined the neural correlates of affective memory processing for both encoding and retrieval in adolescents with MDD compared to controls using functional MRI. Subsequently, we aimed to consider age-related effects and group-by-age interactions, in this cross sectional sample, and the association with affective memory biases as a potential marker of developmental influences on the neural systems sub-serving memory encoding and retrieval processes. We also considered the neural correlates of depression symptom severity.