Obliviate! Reviewing Neural Fundamentals of Intentional Forgetting from a Meta-Analytic Perspective

Intentional forgetting (IF) is an important adaptive mechanism necessary for correct memory functioning, optimal psychological wellbeing, and appropriate daily performance. Due to its complexity, the neuropsychological processes that give birth to successful intentional forgetting are not yet clearly known. In this study, we used two different meta-analytic algorithms, Activation Likelihood Estimation (ALE) & Latent Dirichlet Allocation (LDA) to quantitatively assess the neural correlates of IF and to evaluate the degree of compatibility between the proposed neurobiological models and the existing brain imaging data. We found that IF involves the interaction of two networks, the main “core regions” consisting of a primarily right-lateralized frontal-parietal circuit that is activated irrespective of the paradigm used and sample characteristics and a second less constrained “supportive network” that involves frontal-hippocampal interactions when IF takes place. Additionally, our results support the validity of the inhibitory or thought suppression hypothesis. The presence of a neural signature of IF that is stable regardless of experimental paradigms is a promising finding that may open new venues for the development of effective clinical interventions.

Item method directed forgetting occurs independently of borderline personality traits, even for borderline-salient items

Clinical populations sometimes demonstrate difficulties forgetting stimuli related to their trauma-related disorder, perhaps because their intense personal connection to these stimuli produce deficits in the inhibitory control abilities necessary for forgetting. The present work examined this possibility for people who have high levels of traits implicated in borderline personality disorder (BPD). In two well-powered studies, we found no evidence for deficits in forgetting specific to BPD traits, even for people with clinically significant levels of the traits, contrary to previous studies. The present experiments updated the designs from earlier experiments to employ the most contemporary methods to examine directed forgetting recommended by recent reviews. With these improved methods, Study 1 found that participants showed significant directed forgetting for BPD-related words independent of their level of BPD traits, perhaps because the BPD-related words were so strongly associated with one another. Study 2 found that when we removed the strong relatedness between the stimuli, forgetting of BPD-relevant words was significant and did not interact with BPD symptomology. We concluded that in contrast to people with PTSD who show specific inhibitory deficits for trauma-related works, people with BPD show normal, intact inhibitory control even for words that they should find threatening.

The influence of cue probability on item and source judgments in item method directed forgetting

The current study examined how selective rehearsal strategies in item method directed forgetting are influenced by the probability of remember or forget cues from different sources. In four experiments, study words were presented by one of two sources in an item method directed forgetting paradigm. In all experiments, one source was mostly-remember (presenting twice as many remember as forget words) and the other source was mostly-forget (presenting twice as many forget as remember words). Participants completed item recognition tests (providing cue tags in Experiment 2) with source judgments. Item recognition of forget words was generally greater for the mostly-remember source than for the mostly forget source, whereas recognition of remember words was largely unaffected by source cue probability. Source judgments were consistent with heuristic guessing based on memory strength and knowledge of source cue probability. Experiment 4 analysed overt rehearsal, and showed that words from the mostly-remember source were more likely to be rehearsed prior to the memory cue. Results are discussed in terms of the influence that source cue probability knowledge has on selective rehearsal strategies, recognition decisions, and source memory attributions.

Age-Related Differences in Intentional Forgetting of Prospective Memory

This study investigated age-related differences in intentional forgetting (IF) of prospective memory (memory for actions to be performed in the future) in young (19-30 years) and late-midlife adults (LMA; 57-75 years). Prospective memory (PM) performance was examined by using the Virtual Week (VW) Task. An IF procedure was embedded into the VW task and the participants were instructed to forget some of the PM tasks that they were to remember and execute later on a virtual day. The study compared performances of the young and the LMA participants in the context of event- or time-based regular and irregular tasks. The results confirmed previous findings in showing that LMA participants exhibited worse PM than younger participants in lab-based tasks. In addition, although PM and IF performances separately have been shown to be affected by cognitive aging, larger age-related differences were not found in PM performance under IF conditions.

More Is Less: Increased Processing of Unwanted Memories Facilitates Forgetting

The intention to forget can produce long-lasting effects. This ability has been linked to suppression of both rehearsal and retrieval of unwanted memories, processes mediated by the prefrontal cortex and hippocampus. Here, we describe an alternative account in which the intention to forget is associated with increased engagement with the unwanted information. We used pattern classifiers to decode human functional magnetic resonance imaging data from a task in which male and female participants viewed a series of pictures and were instructed to remember or forget each one. Pictures followed by a forget instruction elicited higher levels of processing in the ventral temporal cortex compared with those followed by a remember instruction. This boost in processing led to more forgetting, particularly for items that showed moderate (vs weak or strong) activation. This result is consistent with the nonmonotonic plasticity hypothesis, which predicts weakening and forgetting of memories that are moderately activated.SIGNIFICANCE STATEMENT The human brain cannot remember everything. Forgetting has a critical role in curating memories and discarding unwanted information. Intentional forgetting has traditionally been linked to passive processes, such as the withdrawal of sustained attention or a stoppage of memory rehearsal. It has also been linked to active suppression of memory processes during encoding and retrieval. Using functional magnetic resonance imaging and machine-learning methods, we show new evidence that intentional forgetting involves an enhancement of memory processing in the sensory cortex to achieve desired forgetting of recent visual experiences. This enhancement temporarily boosts the activation of the memory representation and renders it vulnerable to disruption via homeostatic regulation. Contrary to intuition, deliberate forgetting may involve more rather than less attention to unwanted information.

On the Very-Long-Term Effect of Managing One's Own Memory: The Intention to Forget Improves Recognition After a Year's Delay

While such factors as demand characteristics, encoding, and retrieval inhibition were shown to be significant in producing the directed forgetting effect, no attention was paid to whether the intention to manage one's own memory, per se, matters. In the present article, we addressed this important gap in the literature. To control the quality of encoding we ensured that both the to-be-remembered (TBR) and to-be-forgotten (TBF) items were genuinely learned before the manipulation. We used extremely long delays between the memory instructions and testing to release inhibition associated with the content of instructions. 98 participants demonstrated flawless recall of 12 Russian - made up language word pairs. They then viewed each Russian word from a pair once, with randomized instructions "Forget", "Remember", "Repeat", or a short cognitive task. Self-reports on the mnemonic strategies were collected. Free recall and recognition tests were administered three times - 45 minutes, a month and a year (N = 58) later. Despite a strong incentive to recall all word pairs, fewer TBF pairs were recalled in comparison with TBR pairs, both after 45 minutes and after one month's delay. Recognition among all conditions was equally high. A year later free recall was close to zero. In contrast, the TBR and TBF pairs were recognized equally better than pairs presented in "Repeat" and "Task" conditions. Thus, our results show that the intention to manage one's own memory enhances the accessibility of memories at a very long time delay, no matter what type of instruction is issued.

The effect of positive and negative memory bias on anxiety and depression symptoms among adolescents

OBJECTIVE

To examine the interaction effect of anxiety and depression on the intentional forgetting of positive and negative valence words.

METHODS

One hundred fifty-five grade 7 to grade 10 students participated in the study. The item-method directed forgetting paradigm was used to examine the intentional forgetting of positive-valence, negative-valence, and neutral-valence words.

RESULTS

Negative-valence words were recognized better than either positive-valence or neutral-valence words. The results revealed an anxiety main effect (p = .01, LLCI = -.09, and ULCI = -.01) and a depression main effect (p = .04, LLCI = .00, and ULCI = .24). The anxiety score was negative, whereas the depression score was positively related to the directed forgetting of negative-valence words. Regression-based moderation analysis revealed a significant anxiety × depression interaction effect on the directed forgetting of positive-valence words (p = .02, LLCI = .00, and ULCI = .01). Greater anxiety was associated with more directed forgetting of positive-valance words only among participants with high depression scores. With negative-valence words, the anxiety × depression interaction effect was not significant (p = .15, LLCI = - .00, and ULCI = .01).

CONCLUSION

Therapeutic strategies to increase positive memory bias may reduce anxiety symptoms only among those with high depression scores. Interventions to reduce negative memory bias may reduce anxiety symptoms irrespective of levels of depression.

The challenge of forgetting: Neurobiological mechanisms of auditory directed forgetting

Directed forgetting (DF) is considered an adaptive mechanism to cope with unwanted memories. Understanding it is crucial to develop treatments for disorders in which thought control is an issue. With an item-method DF paradigm in an auditory form, the underlying neurocognitive processes that support auditory DF were investigated. Subjects were asked to perform multi-modal encoding of word-stimuli before knowing whether to remember or forget each word. Using functional magnetic resonance imaging, we found that DF is subserved by a right frontal-parietal-cingulate network. Both qualitative and quantitative analyses of the activation of this network show converging evidence suggesting that DF is a complex process in which active inhibition, attentional switching, and working memory are needed to manipulate both unwanted and preferred items. These results indicate that DF is a complex inhibitory mechanism which requires the crucial involvement of brain areas outside prefrontal regions to operate over attentional and working memory processes. Hum Brain Mapp 39:249-263, 2018. © 2017 Wiley Periodicals, Inc.

The representational consequences of intentional forgetting: Impairments to both the probability and fidelity of long-term memory

We investigated whether intentional forgetting impacts only the likelihood of later retrieval from long-term memory or whether it also impacts the fidelity of those representations that are successfully retrieved. We accomplished this by combining an item-method directed forgetting task with a testing procedure and modeling approach inspired by the delayed-estimation paradigm used in the study of visual short-term memory (STM). Abstract or concrete colored images were each followed by a remember (R) or forget (F) instruction and sometimes by a visual probe requiring a speeded detection response (E1-E3). Memory was tested using an old-new (E1-E2) or remember-know-no (E3) recognition task followed by a continuous color judgment task (E2-E3); a final experiment included only the color judgment task (E4). Replicating the existing literature, more "old" or "remember" responses were made to R than F items and RTs to postinstruction visual probes were longer following F than R instructions. Color judgments were more accurate for successfully recognized or recollected R than F items (E2-E3); a mixture model confirmed a decrease to both the probability of retrieving the F items as well as the fidelity of the representation of those F items that were retrieved (E4). We conclude that intentional forgetting is an effortful process that not only reduces the likelihood of successfully encoding an item for later retrieval, but also produces an impoverished memory trace even when those items are retrieved; these findings draw a parallel between the control of memory representations within working and long-term memory.

When forgetting preserves memory

There has been a resurgence of interest in defining the circumstances leading to memory modifications. Studies have shown that reactivating a supposedly stable memory re-introduces a time-limited window of plasticity during which presentation of interfering material can cause long-term memory changes. The present study asks whether such memory changes can be prevented if people are instructed to forget the memory before the new material is encoded. Participants learned a set of objects. After 48 h, they were reminded of this learning episode, and learned another set of objects. Again 48 h later, they recalled the first (Exp. 1) or second set (Exp. 3). As shown previously, a reminder caused intrusions from the second set into recall of the first set. Here I show that the instruction to forget the first set significantly diminished intrusions from the second set, especially when the instruction was given before the new set was encoded in the second session. Experiment 2 suggests that the reduced intrusions were due to list segregation/isolation, rather than temporarily inhibited access to Set 1. Taken together, the study shows that the attempt to forget a memory can immunize it such that the presentation of interfering material has limited effects, and the memory can be recalled unchanged in the future. This is important when veridical memory is essential, such as in eyewitness testimonies.

Intentional forgetting of emotional words after trauma: a study with victims of sexual assault

Following exposure to a trauma, people tend to experience intrusive thoughts and memories about the event. In order to investigate whether intrusive memories in the aftermath of trauma might be accounted for by an impaired ability to intentionally forget disturbing material, the present study used a modified Directed Forgetting task to examine intentional forgetting and intrusive recall of words in sexual assault victims and controls. By including words related to the trauma in addition to neutral, positive, and threat-related stimuli it was possible to test for trauma-specific effects. No difference between the Trauma and the Control group was found for correct recall of to-be-forgotten (F) words or to-be-remembered (R) words. However, when recalling words from R-list, the Trauma group mistakenly recalled significantly more trauma-specific words from F-list. “Intrusive“ recall of F-trauma words when asked to recall R-words was related to symptoms of post-traumatic stress disorder reported on the Impact of Event Scale and the Post-traumatic Diagnostic Scale. The results are discussed in term of a source-monitoring account.