Depressive rumination and the C957T polymorphism of the DRD2 gene.

Depressed individuals who ruminate have difficulties learning from punishment and suppressing task-irrelevant information. The C957T polymorphism of the DRD2 gene, which affects functioning of D2 dopamine receptors (DRD2) that are expressed predominantly in the indirect pathway of the basal ganglia, has been found to influence suppression and punishment learning. Given these associations, we examined in the present study whether depressive rumination is related to the C957T polymorphism in 317 clinically depressed individuals and 317 never-depressed control individuals. A 2 × 2 (diagnostic group ×C957T polymorphism) analysis of variance conducted on depressive rumination scores yielded a significant interaction of group and C957T: Individuals with two 957C alleles reported higher levels of depressive rumination than did individuals with one or two 957T alleles if they were depressed, but not if they were healthy. The present findings suggest that the dopaminergic system and DRD2 are related to the frequency of maladaptive rumination in depressed individuals. Thus, DRD2 may be an important target for the pharmacological treatment of depressive rumination.

Brain activity related to the ability to inhibit previous task sets: an fMRI study.

Switching between tasks requires individuals to inhibit mental representations of the previous task demands and to activate representations of the new demands. To date, investigators have identified only one way to measure task set inhibition-that is, through a backward inhibition (BI) paradigm. In this paradigm, participants take more time to return to a task set that was recently abandoned (e.g., "A" in an ABA task sequence) than to a nonrecently abandoned task set (e.g., CBA), and investigators have demonstrated that this time cost reflects time needed to overcome the inhibition of the recently abandoned task set. To date, however, investigators have not been able to use this paradigm, or any other, to isolate brain activity related to task set inhibition. For example, contrasting the brain activity elicited by ABA and CBA trials will not isolate activity related to task set inhibition, because inhibition occurs during the initial switch away from task A (i.e., ABA). Given that there is currently no way to directly isolate the brain activity related to task set inhibition, we decided instead to examine how brain activity during task switching varies in individuals who are better than others at inhibiting the previous task set. We found that participants who were good at inhibiting previous task sets, as measured with the BI paradigm, exhibited more activity in the basal ganglia and supplementary motor area/premotor area when task switching, as measured via functional magnetic resonance imaging. These findings suggest that activity in these regions plays a role in task set inhibition.

Sensitivity to reward and punishment in major depressive disorder: effects of rumination and of single versus multiple experiences.

In the current study, we examined the postulation that rumination makes it difficult for depressed individuals to learn the exact probability that different stimuli will be associated with punishment. To do so, we induced rumination or distraction in depressed and never-depressed participants and then measured punishment and reward sensitivity with a probabilistic selection task. In this task, participants first learn the probability that different stimuli will be associated with reward and punishment. During a subsequent test phase in which novel combinations of stimuli are presented, participants' sensitivity to reward is tested by measuring their tendency to select the stimuli that were most highly rewarded during training, and their sensitivity to punishment is tested by measuring their tendency to not select the stimuli that were most highly punished during training. Compared with distraction, rumination led depressed participants to be less sensitive to the probability that stimuli will be associated with punishment and relatively less sensitive to punishment than reward. Never-depressed participants and depressed participants who were distracted from rumination were as sensitive to reward as they were to punishment. The effects of rumination on sensitivity to punishment may be a mechanism by which rumination can lead to maladaptive consequences.

When mental inflexibility facilitates executive control: beneficial side effects of ruminative tendencies on goal maintenance.

Although previous research suggests that depressive ruminators tend to become stuck in a particular mind-set, this mental inflexibility may not always be disadvantageous; in some cases, it may facilitate active maintenance of a single task goal in the face of distraction. To evaluate this hypothesis, we tested 98 college students, who differed in ruminative tendencies and dysphoria levels, on two executive-control tasks. One task emphasized fast-paced shifting between goals (letter naming), and one emphasized active goal maintenance (modified Stroop). Higher ruminative tendencies predicted more errors on the goal-shifting task but fewer errors on the goal-maintenance task; these results demonstrated that ruminative tendencies have both detrimental and beneficial effects. Moreover, although ruminative tendencies and dysphoria levels were moderately correlated (r = .42), higher dysphoria levels predicted more errors on the goal-maintenance task; this finding indicates that rumination and dysphoria can have opposing effects on executive control. Overall, these results suggest that depressive rumination reflects a trait associated with more stability (goal maintenance) than flexibility (goal shifting).

Anticipatory and consummatory pleasure and displeasure in major depressive disorder: An experience sampling study.

Pleasure and displeasure can be parsed into anticipatory and consummatory phases. However, research on pleasure and displeasure in major depressive disorder (MDD), a disorder characterized by anhedonia, has largely focused on deficits in the consummatory phase. Moreover, most studies in this area have been laboratory-based, raising the question of how component processes of pleasure and displeasure are experienced in the daily lives of depressed individuals. Using experience sampling, we compared anticipatory and consummatory pleasure and displeasure for daily activities reported by adults with MDD (n = 41) and healthy controls (n = 39). Participants carried electronic devices for one week and were randomly prompted eight times a day to answer questions about activities to which they most and least looked forward. Compared to healthy controls, MDD participants reported blunted levels of both anticipatory and consummatory pleasure and elevated levels of both anticipatory and consummatory displeasure for daily activities. Independent of MDD status, participants accurately predicted pleasure but overestimated displeasure. These results are the first to provide evidence that, across both anticipatory and consummatory phases, individuals with MDD experience blunted pleasure and elevated displeasure for daily activities. Our findings clarify the disturbances in pleasure and displeasure that characterize MDD and may inform treatment for this debilitating disorder. (PsycINFO Database Record

An attentional scope model of rumination.

Rumination, defined as repetitive thinking about negative information, has been found to lead to serious maladaptive consequences, including longer and more severe episodes of major depression. In this review, we present and discuss research findings motivated by the formulation that individual differences in cognitive processes that control how information is processed influence the likelihood that thoughts will become repetitive and negative. Several studies have demonstrated that a tendency to ruminate (i.e., trait rumination) is related to difficulties updating working memory (WM) and disengaging from and forgetting no-longer-relevant information. Other investigators have documented that trait rumination is also associated with an enhanced ability to ignore distracting information and with more stable maintenance of task-relevant information. In contrast to trait rumination, a state of rumination has been found to be related to widespread deficits in cognitive control. In this article, we discuss how the current accounts of control functioning cannot explain this pattern of anomalous control functioning. To explain these findings, including unexpected and contradictory results, we present an attentional scope model of rumination that posits that a constricted array of thoughts, percepts, and actions that are activated in WM or available for selection from long-term memory affects the control functioning of trait ruminators. This model explains, at a cognitive level, why rumination is particularly likely to arise when individuals are in a negative mood state; it also accounts for a number of findings outside of the rumination-control literature and generates several novel predictions.

Switching and backward inhibition in major depressive disorder: the role of rumination.

Previous studies have demonstrated that individuals with major depressive disorder have difficulties switching attention from one task set to another. In the current study we examined whether ruminative thinking drives the switching deficits of depressed individuals. A secondary, more exploratory, goal of this study was to examine whether state rumination would impair depressed individuals' ability to activate a new task set, to inhibit a no longer relevant task set, or both. Participants underwent either a rumination induction or a distraction induction and then completed a backward inhibition task that measures general switching abilities and the ability to inhibit previous task sets. Although depression was not related to switching ability as a main effect, depressed individuals who were induced to ruminate exhibited poorer switching ability than did both depressed and control individuals who were distracted from ruminating and control participants who were induced to ruminate. These findings suggest that depressed individuals are characterized by switching deficits only if they are ruminating. Moreover, the finding that state rumination did not affect participants' ability to inhibit previous task sets suggests that state rumination primarily impairs noninhibitory task-switching processes. It is interesting that the opposite pattern of results was obtained for trait rumination, which was related to inhibitory deficits during switching, but not to generally poorer switching. Thus, state and trait rumination may be associated with dissociable cognitive deficits.

Cognitive control mechanisms, emotion and memory: a neural perspective with implications for psychopathology.

In this paper we provide a focused review of the literature examining neural mechanisms involved in cognitive control over memory processes that can influence, and in turn are influenced by, emotional processes. The review is divided into two parts, the first focusing on working memory and the second on long-term memory. With regard to working memory, we discuss the neural bases of (1) control mechanisms that can select against distracting emotional information, (2) mechanisms that can regulate emotional reactions or responses, (3) how mood state influences cognitive control, and (4) individual differences in control mechanisms. For long-term memory, we briefly review (1) the neural substrates of emotional memory, (2) the cognitive and neural mechanisms that are involved in controlling emotional memories and (3) how these systems are altered in post-traumatic stress disorder. Finally, we consider tentative generalizations that can be drawn from this relatively unexplored conjunction of research endeavors.

Inhibition versus switching deficits in different forms of rumination.

Individuals who depressively ruminate about their current dysphoria tend to perseverate more than nonruminators. The goal of the current study was to determine whether such perseverative tendencies are associated with an inability to switch attention away from old to new information or with an inability to effectively inhibit the processing of previously relevant information. We used a task-switching paradigm that can distinguish between these two processes. Two experiments showed that depressive rumination is associated with a deficit in inhibiting prior mental sets. The second experiment also demonstrated that, in contrast to depressive rumination, angry and intellectual rumination are associated with difficulties in switching to a new task set, but not with inhibition of a prior task set. This study suggests that different forms of rumination are associated with different cognitive mechanisms and that both deficits may contribute to the perseveration that is associated with ruminative tendencies.