Reglas Administrativas

3.1 Evidence in adults

Perlstein et al. (2002) were the first, to our knowledge, to investigate the influence of emotional content on WM performance. Using a delayed match-to-sample task with pleasant, unpleasant and neutral IAPS pictures, they found that the increase in dlPFC activation during the delay varied according to the valence of the stimuli.

GENERAL INTRODUCTION

31 Activity in this WM-related region was larger for pleasant and smaller for unpleasant pictures, as compared to neutral stimuli, and behavioural performance (in a larger sample) followed this effect, with better WM performance for positive and impaired WM performance for negative pictures. Kensinger and Corkin (2003) followed-up on these findings in a series of behavioural studies, and only found an effect on an n-back task using faces. More specifically, participants responded slower to fearful than neutral faces. Other WM tasks (e.g. word span tasks and an n-back task with words) did not show emotional interference effects. Increased saliency of faces compared to words might explain this selective effect, given that faces are biologically relevant stimuli (Rellecke, Palazova, Sommer, & Schacht, 2011; Vuilleumier, 2005). Indeed, several studies have replicated the finding that emotional facial expressions impact WM, although findings about valence-specific effects are mixed. While some studies have shown enhanced performance for positive faces (D'Argembeau & Van der Linden, 2007;

D'Argembeau, Van der Linden, Etienne, & Comblain, 2003; Fales, Becerril, Luking, &

Barch, 2010), others have reported improved performance for negative faces (Jackson, Linden, & Raymond, 2014; Kensinger & Corkin, 2003).

In addition to the abovementioned studies where emotional stimuli were central to the task goal, other researchers have examined the role of emotional distraction on WM. For example, Dolcos and McCarthy (2006) have compared the effect of emotional and non-emotional distractors presented during the delay interval of a WM task.

Activity in typical WM regions, such as the dlPFC and lateral parietal cortex (LPC), was found to depend on the distractor type. Emotional distractors during the delay resulted in a relative deactivation of these WM regions, and increased activity in regions traditionally implicated in emotional processing, such as the amygdala and vlPFC.

Moreover, this pattern was related to impaired performance, suggesting that activity in ventral emotional regions disrupts activation of the dorsal system linked to WM maintenance.

Since WM processes are thought to play an important role in the etiology of depression, and more specifically rumination (Joormann, Yoon, & Zetsche, 2007), a number of studies have compared maintenance of (negatively) valenced information in WM in healthy and depressed adults. Indeed, Joormann and Gotlib (2008) have shown that depressed individuals had more difficulties removing negative material from WM

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than controls, even when compared to never-depressed individuals in a sad mood.

Research by Levens and Gotlib (2010) led to the same conclusion, with depressed individuals showing a tendency to keep negative material active in WM, while healthy controls tended to keep positive information in mind.

WM is also an important component implicated in cognitive theories of anxiety, such as Attentional Control Theory (ACT; Derakshan & Eysenck, 2009; Eysenck &

Derakshan, 2011). ACT builds on the WM model of Baddeley (1986), which divides WM into three components: 1) the phonological loop, responsible for rehearsing and storing verbal content, 2) the visuo-spatial sketchpad, underlying the processing and maintenance of visual and spatial information, and 3) the central executive, which is a supervisory attentional system controlling information processing. According to ACT, anxiety will have an impact on the central executive, while effects on the other components are thought to be only modest. Furthermore, based on evidence indicating that the central executive can be subdivided into an inhibition, shifting and updating function (Miyake et al., 2000), recent accounts of the ACT suggest that anxiety impairs the inhibition and shifting function. These predictions have received considerable support thus far (for a review, see Derakshan & Eysenck, 2009; Eysenck & Derakshan, 2011).

Given the involvement of WM deficits in depression and anxiety, questionnaires measuring both are included in all empirical chapters in this thesis (Chapter 3-5) and correlations with performance or neural activation are examined. Furthermore, in Chapter 5, we examined WM for emotional information in students at risk for developing mood disorders.

3.2 Emotional working memory in adolescents

As noted before, studies examining emotional WM in adolescents are rather scarce. In a couple of studies, Ladouceur and colleagues have investigated the interference of irrelevant affective information while performing a standard WM task (Ladouceur et al., 2005; Ladouceur et al., 2013; Ladouceur et al., 2009; Tavitian et al., 2014). In a study using neutral, positive or negative IAPS pictures as distractors, healthy controls were more easily distracted by positive backgrounds, as suggested by longer reaction times, while depressed or comorbid anxious/depressed adolescents performed

GENERAL INTRODUCTION

33 worse when negative background pictures were used (Ladouceur et al., 2005). In a similar paradigm that has been used in several studies (Ladouceur et al., 2013;

Ladouceur et al., 2009; Tavitian et al., 2014) happy, neutral and angry faces were shown as distractors, instead of IAPS pictures. Results showed that high anxious participants responded slower on a high load condition with fearful faces (Ladouceur et al., 2009), and that depressed adolescents performed worse for neutral faces independent of memory load (Tavitian et al., 2014). Together, these findings indicate perturbed processing of emotional information in both anxious as well as depressed adolescents.

Furthermore, the finding that healthy controls were more easily distracted by positive backgrounds is in line with theories proposing hypersensitivity to (positive) emotional information during adolescence (Ernst et al., 2006; Somerville & Casey, 2010; Steinberg, 2008). However, it is unclear whether this pattern is also evident in adults, since none of these studies directly compared performance across these age groups.

In addition to these studies investigating interference of emotional distractors, Passarotti and colleagues (Passarotti, Sweeney, & Pavuluri, 2010; Schenkel, Passarotti, Sweeney, & Pavuluri, 2012) have examined how relevant affective content is manipulated in WM. Healthy controls were found to activate emotion regulation and WM regions more for angry compared to neutral faces, while activation was diminished in these regions for the happy versus neutral faces. Unfortunately, the relationship between this activation pattern and behavioural performance was not examined thus limiting the interpretation of this finding.

To conclude, while affective modulation of WM processes have clearly been shown in adults, evidence in adolescents is very limited. Furthermore, these studies have focused on clinical populations, leaving the development of emotional WM in healthy adolescents understudied. Moreover, previous studies have often used a wide age range and have not compared adolescents’ performance to that of adults. Thus, it is unclear whether the patterns observed in healthy controls are general mechanisms also present in adulthood or whether they are specific to adolescents.

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