Academic journal article Cognitive, Affective and Behavioral Neuroscience

Poor Performance on Cognitive Tasks in Depression: Doing Too Much or Not Enough?

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Poor Performance on Cognitive Tasks in Depression: Doing Too Much or Not Enough?

Article excerpt

Depressed people perform poorly on cognitive tasks. It is unclear whether these deficits are due to decreased devotion of task-related resources or to increased attention to non-task-related information. In the present study, we examined the degree to which depressed and healthy adults displayed pupillary motility that varied at the frequency of presented stimuli on a cognitive task, which we interpreted as task-related processing, and at other frequencies, which we interpreted as reflecting intrinsic processing. Depressed participants made more consecutive errors than did controls. More pupillary motility at other frequencies was associated with poorer performance, whereas more pupillary motility at the frequency of presented stimuli was associated with better performance. Depressed participants had more pupillary motility at other frequencies, which partially mediated observed deficits in cognitive performance. These findings support the hypothesis that allocating cognitive resources to intrinsic processing contributes to observed cognitive deficits in depression.

Clinically depressed adults demonstrate deficits in cognitive control (Austin, Mitchell, & Goodwin, 2001; Ottowitz, Tondo, Dougherty, & Savage, 2002; Rogers et al., 2004). Cognitive control facilitates, among other faculties, the following: attention allocation, encoding goalrelevant information, the inhibition of processing of irrelevant information, monitoring performance, and using feedback to adjust future responding (MacDonald, Cohen, Stenger, & Carter, 2000; Ridderinkhof, Ullsperger, Crone, & Nieuwenhuis, 2004). In particular, relative to healthy controls, depressed individuals demonstrate abnormal (either hyper- or hypo-) activity in neural regions underlying cognitive control and poor behavioral performance during demanding cognitive tasks (Holmes & Pizzagalli, 2008; Okada, Okamoto, Morinobu, & Yamawaki, 2003; Pizzagalli, Peccoralo, Davidson, & Cohen, 2006).

The reasons for poor performance during cognitive tasks in depression are unclear. The tendency to engage in intrinsic processing-for example, focusing on negative automatic thoughts-has been hypothesized to use cognitive resources that would otherwise be allocated to a cognitive task resulting in poor performance (Christopher & Mac- Donald, 2005; Holmes & Pizzagalli, 2007, 2008). Consistent with this hypothesis, relative to controls, depressed participants demonstrate a hyperactivation in neural regions that are implicated in affective processing, such as the rostral anterior cingulate, after making an initial error on a demanding cognitive task, which is subsequently associated with a failure to recruit dorsolateral prefrontal cortex (DLPFC) based cognitive control and poorer subsequent performance on the task (Holmes & Pizzagalli, 2008). Similarly, depressed participants who were experimentally induced to ruminate-that is, to repetitively focus on themselves and the nature and implications of their negative feelings (Nolen-Hoeksema, 1991; Watkins & Brown, 2002), prior to engaging in a cognitive task-experienced more sadness and intrinsic intrusive thoughts and produced more errors than they did when they were induced to engage in distraction by focusing on external information unrelated to symptoms or feelings (Watkins & Brown, 2002). Furthermore, depressed participants demonstrate difficulty inhibiting irrelevant negative material from working memory (Joormann & Gotlib, 2008). Thus, studies could suggest that depressed individuals engage in increased intrinsic processing that potentially depletes or taxes the ability to engage in controlled processing of information.

Alternately, evidence suggests that poor cognitive performance may be more related to a lack of cognitive resources that are necessary to do the task independent of engaging in intrinsic processing. Some investigations have demonstrated deficits in behavioral performance, which coincides with decreased neural activation in brain regions that are critical for cognitive control in the absence of activity in neural regions that are implicated in emotional processing (Audenaert et al. …

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