Cognitive and neural consequences of memory suppression in major depressive disorder.

Negative biases in cognition have been documented consistently in major depressive disorder (MDD), including difficulties in the ability to control the processing of negative material. Although negative information-processing biases have been studied using both behavioral and neuroimaging paradigms, relatively little research has been conducted examining the difficulties of depressed persons with inhibiting the retrieval of negative information from long-term memory. In this study, we used the think/no-think paradigm and functional magnetic resonance imaging to assess the cognitive and neural consequences of memory suppression in individuals diagnosed with depression and in healthy controls. The participants showed typical behavioral forgetting effects, but contrary to our hypotheses, there were no differences between the depressed and nondepressed participants or between neutral and negative memories. Relative to controls, depressed individuals exhibited greater activity in right middle frontal gyrus during memory suppression, regardless of the valence of the suppressed stimuli, and differential activity in the amygdala and hippocampus during memory suppression involving negatively valenced stimuli. These findings indicate that depressed individuals are characterized by neural anomalies during the suppression of long-term memories, increasing our understanding of the brain bases of negative cognitive biases in MDD.

Distracted by cues for suppressed memories.

We examined the potential cost of practicing suppression of negative thoughts on subsequent performance in an unrelated task. Cues for previously suppressed and unsuppressed (baseline) responses in a think/no-think procedure were displayed as irrelevant flankers for neutral words to be judged for emotional valence. These critical flankers were homographs with one negative meaning denoted by their paired response during learning. Responses to the targets were delayed when suppression cues (compared with baseline cues and new negative homographs) were used as flankers, but only following direct-suppression instructions and not when benign substitutes had been provided to aid suppression. On a final recall test, suppression-induced forgetting following direct suppression and the flanker task was positively correlated with the flanker effect. Experiment 2 replicated these findings. Finally, valence ratings of neutral targets were influenced by the valence of the flankers but not by the prior role of the negative flankers.

Interpretive habit is strengthened by cognitive bias modification.

We investigated the nature of the memory mechanisms underlying cognitive bias modification by applying Jacoby's (1991) process-dissociation procedure to responses during the transfer task. In the two training conditions (negative and benign), students imagined themselves in 100 ambiguous scenarios, most with potentially negative resolutions; the ambiguity was resolved in a consistently negative or benign direction by completing the fragment of a final word. Control participants completed non-ambiguous, non-emotional scenarios. Next all participants responded on a final training block, where half of the scenarios were completed negatively and half benignly. Transfer was assessed by examining choices in the completion of test scenarios when participants were instructed to respond in the same way as they had to a final-block training scenario that was situationally similar. Benign training facilitated correct responding to benign analogues and impaired correct responding to negative analogues. Performance in the negative-training and control conditions was similar. Process-dissociation procedures revealed that this newly established habit and not controlled recollection provided the basis for transfer.

Stuck in the past? Rumination-related memory integration.

Memories connected to ruminative concerns repetitively capture attention, even in situations designed to alter them. However, recent research on memory updating suggests that memory for benign substitutes (e.g., reinterpretations) might be facilitated by integration with the ruminative memories. As a first approach, two experiments (Ns = 72) mimicked rumination-related memories with rumination-themed stimuli and an imagery task. College undergraduates screened for ruminative status first studied and imaged ruminative cue-target word pairs, and then in a second phase they studied the same cues re-paired with benign targets (along with new and repeated pairs). On the test of cued recall of benign targets, they judged whether each recalled word had been repeated or changed across the two phases (or was new in the second phase). When target changes were not remembered, recall of benign targets revealed proactive interference that was insensitive to ruminative status. However, when participants remembered change and the ruminative targets, their recall of benign targets was facilitated, particularly if they identified as ruminators (Experiment 1). When the test simply asked for recall of either or both targets (Experiment 2), ruminators recalled both targets more frequently than did others. These outcomes suggest that ruminative memories might provide bridges to remembering associated benign memories, such as reinterpretations, under conditions consistent with everyday ruminative retrieval.

Suppression-induced forgetting on a free-association test.

The repeated suppression of thoughts in response to cues for their expression leads to forgetting on a subsequent test of cued recall (Anderson & Green, 2001). We extended this effect by using homograph cues and presenting them for free association following suppression practice. Cue-target pairs were first learned under integrating imagery instructions; then in the think/no-think phase students practised suppressing thoughts connected to some homograph cues, with or without the assistance of thought substitutes that changed their meaning. Below-baseline forgetting on the subsequent free-association test was found in the production of suppressed targets. Following aided suppression this effect was also obtained in the production of other responses denoting the target-related meaning of the homograph cues. Discussion emphasises the ecological value of the test; rarely do people deliberately attempt recall of unwanted thoughts.

Brooding deficits in memory: focusing attention improves subsequent recall.

Ruminative habits of thought about one's problems and the resulting consequences are correlated with symptoms of depression and cognitive biases (Nolen-Hoeksema, Wisco, & Lyubomirsky, 2008). In our orienting task, brooders and non-brooders concentrated on self-focusing phrases while they were also exposed to neutral target words. On each trial in the unfocused condition, participants saw and then reported the target before concentrating on the phrase; in the focused condition, the target was reported after phrase concentration. A brooding-related deficit on a subsequent unexpected test of free and forced recall was obtained in the unfocused condition only. Brooders recalled more successfully in the focused than in the unfocused condition. Thus, impaired recall of material unrelated to self-concerns may be corrected in situations that constrain attention.

Biases in interpretation and memory in generalized social phobia.

Two experiments examined the link between interpretation and memory in individuals diagnosed with Generalized Social Phobia (GSP). In Experiment 1, GSP and control participants generated continuations for nonsocial and ambiguous social scenarios. GSP participants produced more socially anxious and negative continuations for the social scenarios than did the controls. On the subsequent test of recalling the social scenarios, intrusion errors that shared meaning with the original continuations were made more frequently by the GSP group, producing false recall with emotionally negative features. To examine whether nonanxious individuals would also produce such errors if given emotional interpretations, in Experiment 2 the authors asked university students to read the scenarios plus endings produced by GSP participants in Experiment 1. The students either constructed vivid mental images of themselves as the main characters or thought about whether the endings provided closure. Low-anxious students in the closure condition produced fewer ending-based intrusions in recalling the social scenarios than did students in the other 3 conditions. Results illustrate the importance of examining the nature of source-monitoring errors in investigations of memory biases in social anxiety.

Depression-related differences in learning and forgetting responses to unrelated cues.

Using the think/no-think paradigm, we examined the effect of a meaningful connection between emotionally neutral cues and targets on initial learning and later recall by students in dysphoric or nondysphoric mood states. Compared to meaningfully connected cue-target pairs, unrelated pairs were less easily learned and more easily forgotten, even when initial learning was controlled. Depressive deficits were obtained in initial learning (only marginally) and final recall. When examined separately within each cuing condition, the recall deficit associated with depressed mood was restricted to the unrelated condition, but when initial learning differences were controlled this deficit was only marginally significant. Results are discussed in relation to other recent findings concerning depression-related performance in this paradigm and to findings of depression and memory more generally.

Am I blue? Depressed mood and the consequences of self-focus for the interpretation and recall of ambiguous words.

In two experiments, dysphoric and nondysphoric students first concentrated on either self-focused or other-focused phrases and then performed an ostensibly unrelated task involving the interpretation of homographs with both personal and impersonal meanings. In Experiment 1, they constructed sentences for the homographs; dysphoric students' sentences were more emotionally negative (although not more personal) in the self-focused condition than in the other-focused condition. In Experiment 2, they freely associated to the homographs, and the percentage of personal meanings reflected by the associations revealed an effect of self versus other focus that depended on mood group. Following free associations, they attempted to recall the homographs. Dysphoric students (but not nondysphoric students) recalled a greater percentage of personally interpreted homographs if they had focused on self than if they had focused on other matters. In general, these results suggest that ruminative or self-focused thinking by people in depressed moods transfers to novel ambiguous situations, encouraging more negative interpretations and better recall of personal interpretations.

Practicing Emotionally Biased Retrieval Affects Mood and Establishes Biased Recall a Week Later.

Cognitive Bias Modification (CBM) can yield clinically relevant results. Only few studies have directly manipulated memory bias, which is prominent in depression. In a new approach to CBM, we sought to simulate or oppose ruminative processes by training the retrieval of negative or positive words. Participants studied positive and negative word pairs (Swahili cues with Dutch translations). In the positive and negative conditions, each of the three study trials was followed by a cued-recall test of training-congruent translations; a no-practice condition merely studied the pairs. Recall of the translations was tested after the training and after 1 week. Both recall tests revealed evidence of training-congruent bias and bias was associated with emotional autobiographical memory. Positive retrieval practice yielded stable positive mood, in contrast to the other conditions. The results indicate that memory bias can be established through retrieval practice and that the bias transfers to mood and autobiographical memory.

Remembering the good, forgetting the bad: intentional forgetting of emotional material in depression.

The authors examined intentional forgetting of negative material in depression. Participants were instructed to not think about emotional nouns that they had learned to associate with a neutral cue word. The authors provided participants with multiple occasions to suppress the unwanted words. Overall, depressed participants successfully forgot negative words. Moreover, the authors obtained a clear practice effect. However, forgetting came at a cost: Compared with the nondepressed participants and with the depressed participants who were instructed to forget positive words, depressed participants who were instructed to forget negative words showed significantly worse recall of the baseline words. These results indicate that training depressed individuals in intentional forgetting could prove to be an effective strategy to counteract automatic ruminative tendencies and mood-congruent biases.

Intentional forgetting benefits from thought substitution.

This study provides both experimental and correlational evidence that forgetting in the think/no-think paradigm (Anderson & Green, 2001) is sensitive to the substitution of thoughts about new events for thoughts that are to be suppressed. All the participants learned a list of adjective-noun pairs. Then the adjectives were presented as cues for recalling half of the nouns and as cues for suppressing the other half, 0, 2, or 12 times. Aided participants were provided with substitute nouns, to use during suppression. On a final test that requested recall of all initially learned nouns, aided participants showed evidence of below-baseline forgetting of suppressed nouns. Unaided participants produced below-baseline forgetting only if their later self-reports indicated that they had complied relatively well with instructions for suppression. Independently, forgetting in the unaided condition was more successful when the participants reportedly thought about something else during suppression trials. In general, the use of self-initiated strategies seems to affect the degree of forgetting in the think/no-think paradigm.

Suppression-Induced Reduction in the Specificity of Autobiographical Memories.

To extend its relevance to everyday forgetting, we applied the think/no-think (TNT) suppression method devised by Anderson and Green (2001) to autobiographical memories. Dysphoric and nondysphoric participants first generated autobiographical memories and corresponding titles to neutral and emotionally positive or negative cues. During the TNT phase, participants repeatedly practiced responding to some cues with their associated titles and avoiding thoughts about titles and memories associated with other cues. Later, they were asked to report memories associated with all cues, including baseline cues not presented during the TNT phase. Results revealed impaired recall, as measured by reductions in specificity, for suppressed memories relative to baseline memories. Also, regardless of TNT instructions, memories of dysphoric students who had received negative cues became less specific and less negative than they were at the outset.

Cognitive Bias Modification: Past Perspectives, Current Findings, and Future Applications.

Research conducted within the general paradigm of cognitive bias modification (CBM) reveals that emotional biases in attention, interpretation, and memory are not merely associated with emotional disorders but contribute to them. After briefly describing research on both emotional biases and their modification, the authors examine similarities between CBM paradigms and older experimental paradigms used in research on learning and memory. The techniques and goals of CBM research are compared with other approaches to understanding cognition-emotion interactions. From a functional perspective, the CBM tradition reminds us to use experimental tools to evaluate assumptions about clinical phenomena and, more generally, about causal relationships between cognitive processing and emotion.

Recollection is impaired by the modification of interpretation bias.

The interpretation paradigm of cognitive-bias modification (CBM-I) was modified with instructions used in process-dissociation procedures for the purpose of investigating processes contributing to performance on the transfer task. In Experiment 1, nonanxious students were trained to interpret ambiguous situations in either a negative or benign way (or they read nonambiguous scenarios). They were then asked to respond to new ambiguous situations, in the same way as contextually similar analogues during training, or to respond differently. Benign training proactively impaired memory for negative outcomes. This effect was replicated by anxious students in Experiment 2 and discussed with respect to the assumptions underlying process-dissociation procedures and directions for future research.

Cognitive bias modification: induced interpretive biases affect memory.

Previous research has shown that it is possible to experimentally induce interpretive biases using ambiguous scenarios. This study extends past findings by examining the effects of cognitive bias modification for interpretation on subsequent scenario recall. Participants were trained to interpret emotionally ambiguous passages in either a positive or negative direction. Transfer of the training to novel scenarios was tested. After training, participants were also asked to recall details from these novel scenarios. The results indicate that the training was effective in inducing the intended group differences in interpretive bias. Importantly, participants exhibited memory biases that corresponded to their training condition. These results suggest that manipulating interpretive biases can result in corresponding changes in memory. Findings from this study highlight the importance of future research on the relation among cognitive biases and on the possibility of modifying cognitive biases in emotional disorders.

Training forgetting of negative material in depression.

In this study, the authors investigated whether training participants to use cognitive strategies can aid forgetting in depression. Participants diagnosed with major depressive disorder (MDD) and never-depressed participants learned to associate neutral cue words with a positive or negative target word and were then instructed not to think about the negative targets when shown their cues. The authors compared 3 different conditions: an unaided condition, a positive-substitute condition, and a negative-substitute condition. In the substitute conditions, participants were instructed to use new targets to keep from thinking about the original targets. After the training phase, participants were instructed to recall all targets when presented with the cues. MDD participants, in contrast with control participants, did not exhibit forgetting of negative words in the unaided condition. In both the negative and positive substitute conditions, however, MDD participants showed successful forgetting of negative words and a clear practice effect. In contrast, negative substitute words did not aid forgetting by the control participants. These findings suggest that training depressed individuals to use cognitive strategies can increase forgetting of negative words.

Depressive deficits in forgetting.

The aim of this study was to investigate whether difficulties in forgetting (like difficulties in remembering) are associated with depressive states. First, dysphoric and nondysphoric students learned 40 word pairs, each consisting of a positive or negative adjective and a neutral noun (target). Next, the students practiced responding with some targets and suppressing others, when given the adjective as cue, for a varied number of repetitions. On the final test, they were told to disregard the prior instruction to suppress and to recall the target associated with every cue. Compared with nondysphoric students, dysphoric students recalled similar percentages of targets from sets assigned for response practice but higher percentages from sets assigned for suppression practice. The degree of forgetting showed some mood-congruent tendencies and was significantly correlated with self-report measures of rumination and unwanted thoughts.