Binding and inhibition in episodic memory—Cognitive, emotional, and neural processes

A comment on the Revised Diffusion Model for Conflict tasks (RDMC)

In conflict tasks, such as the Simon, Eriksen flanker, or Stroop task, a relevant and an irrelevant feature indicate the same or different responses in congruent and incongruent trials, respectively. The congruency effect refers to faster and less error-prone responses in congruent relative to incongruent trials. Distributional analyses reveal that the congruency effect in the Simon task becomes smaller with increasing RTs, reflected by a negative-going delta function. In contrast, for other tasks, the delta function is typically positive-going, meaning that congruency effects become larger with increasing RTs. The Diffusion Model for Conflict tasks (DMC; Ulrich et al., Cognitive Psychology, 78, 148-174, 2015) accounts for this by explicitly modeling the information accumulated from the relevant and the irrelevant features and attributes negatively- versus positively-sloped delta functions to different peak times of a pulse-like activation resulting from the task-irrelevant feature. Because the underlying function implies negative drift rates, Lee and Sewell (Psychonomic Bulletin & Review, 31(5), 1-31, 2024) recently questioned this assumption and suggested their Revised Diffusion Model for Conflict tasks (RDMC). We address three issues regarding RDMC compared to DMC: (1) The pulse-like function is not as implausible as Lee and Sewell suggest. (2) RDMC itself comes with a questionable assumption that different parameters are required for congruent and incongruent trials. (3) Moreover, we present data from a new parameter recovery study, suggesting that RDMC lacks acceptable recovery of several parameters (in particular compared to DMC). In this light, we discuss RDMC as not (yet) a revised version of DMC.

Memory modulation: Dominance of negative visual context over neutral verbal memory

Neutral memories can be modulated via intentional memory control paradigms such as directed forgetting. In addition, previous studies have shown that neutral visual memories can be modulated indirectly, via remember and forget instructions towards competing verbal memories. Here we show that direct modulation of neutral verbal memory strength is impaired by negative visual context, and that negative visual context is resistant to indirect memory modulation. Participants were directly instructed to intentionally remember or forget newly encoded neutral verbal information. Importantly, this verbal information was interleaved with embedded negative visual context. Results showed that negative visual context eliminated the well-documented effect of direct instructions to intentionally remember verbal content. Furthermore, negative visual memory was highly persistent, overcoming its sensitivity to indirect modulation shown in previous studies. Finally, these memory effects persisted to the following day. These results demonstrate the dominance of negative visual context over neutral content, highlighting the challenges associated with memory modulation in psychopathologies involving maladaptive processing of negative visual memories.

Episodic Events as Spatiotemporal Memory: The Sequence of Information in the Episodic Buffer of Working Memory for Language Comprehension

Memory and language are the two higher-order cognitive abilities intertwined for communication and other cognitive skills. Memory is the storage capacity of all the information we perceive. Where the sensory memory perceives the stimuli, the working memory actively stores the information and passes it to the long-term memory. However, there is a question that how is the continuous perception of stimuli transformed into meaningful information and organized for proper execution and retrieval from the memory? This paper focuses on the episodic memory that perceives information that is spatial and temporal based on our everyday experiences. Though the spatiotemporal information we receive is continuous; the episodic memory arranges the information as to episodes in the working memory before the information is stored for a longer period. The episodic buffer is one of the components of the working memory model which holds the episodic memory that is organized concerning time. To this point, the paper tries to understand the working of the episodic buffer in maintaining the episodic memory and also about the process of episodic events into meaningful units. Further, the paper also concentrates on the hippocampus which is considered to be the location of the episodic buffer.

Principal component analysis suggests multiple dimensions of memory inhibition that are differentially affected by age

Background

Cognitive inhibition is among the executive functions that decline early in the course of normal aging. Failures to be able to inhibit irrelevant information from memory may represent an essential factor of age-associated memory impairment. While a variety of elaborate behavioral tasks have been developed that presumably all index memory inhibition, the extent to which these different tasks measure the same underlying cognitive construct that declines with age has not been well explored.

Methods

In the current study, 100 and 75 cognitively healthy younger (n = 71; age = 30.7 ± 5.4 years, 56.7% female) and older (n = 104, age = 69.3 ± 5.9 years, 66.2% female) adults with equivalent educational attainment performed three computer-based memory inhibition tasks: the Retrieval Induced Forgetting task, the Suppress task, and the Directed Forgetting task. We conducted a principal component analysis using scores derived from different components of these tasks to explore whether and how the tasks relate to one another. We further investigated how age, sex and education, along with, in a subsample of the participants, a neuropsychological measure of episodic memory, impacted both the task scores individually, and the principal components derived from the exploratory analysis.

Results

We identified 3 distinct sources of variability which represent potentially independent cognitive processes: memory retrieval facilitation, and two memory inhibition processes that distinguished themselves by the degree of volitional initiation of memory suppression. Only the memory retrieval component correlated with a neuropsychologically-derived episodic memory score, and both memory inhibition principal components were age dependent.

Conclusion

Our findings provide support for a distinction in memory suppression processes between those 'instructed' to be performed and those which happen without explicit instruction. This distinction adds nuance to the dichotomous classification of controlled vs. automatic inhibitory mechanisms, which have been shown in previous work to vary as a function of the degree of frontal involvement. Our findings further demonstrate that while both of these measures of inhibition were affected by age, the episodic memory component was not, suggesting that inhibitory impairments may precede memory deficits in healthy aging.

Fake news reminders and veracity labels differentially benefit memory and belief accuracy for news headlines

Fake news exposure can negatively affect memory and beliefs, thus sparking debate about whether to repeat misinformation during corrections. The once-prevailing view was that repeating misinformation increases its believability and should thus be avoided. However, misinformation reminders have more recently been shown to enhance memory and belief accuracy. We replicated such reminder benefits in two experiments using news headlines and compared those benefits against the effects of veracity labeling. Specifically, we examined the effects of labeling real news corrections to enhance conflict salience (Experiment 1) and labeling fake news on its debut to encourage intentional forgetting (Experiment 2). Participants first viewed real and fake news headlines with some fake news labeled as false. Participants then saw labeled and unlabeled real news corrections; labeled corrections appeared alone or after fake news reminders. Reminders promoted the best memory and belief accuracy, whereas veracity labels had selective effects. Correction labels led to intermediate memory and belief accuracy, whereas fake news labels improved accuracy for beliefs more than memory. The extent that real and fake news details were recalled together correlated with overall memory and belief differences across conditions, implicating a critical role for integrative encoding that was promoted most by fake news reminders.

List-method directed forgetting: Do critical findings generalize from short to long retention intervals?

People can purposefully forget information that has become irrelevant, as is demonstrated in list-method directed forgetting (LMDF). In this task, participants are cued to intentionally forget an already studied list (list 1) before encoding a second list (list 2); this induces forgetting of the first-list items. Most research on LMDF has been conducted with short retention intervals, but very recent studies indicate that such directed forgetting can be lasting. We examined in two experiments whether core findings in the LMDF literature generalize from short to long retention intervals. The focus of Experiment 1 was on the previous finding that, with short retention interval, list-2 encoding is necessary for list-1 forgetting to arise. Experiment 1 replicated the finding after a short delay of 3 min between study and test and extended it to a longer delay of 20 min. The focus of Experiment 1 was on the absence of list-1 forgetting in item recognition, previously observed after short retention interval. Experiment 1 replicated the finding after a short delay of 3 min between study and test and extended it to longer delays of 20 min and 24 h. Implications of the results for theoretical explanations of LMDF are discussed.

What do laboratory-forgetting paradigms tell us about use-inspired forgetting?

Directed forgetting is a laboratory task in which subjects are told to remember some information and forget other information. In directed forgetting tasks, participants are able to exert intentional control over which information they retain in memory and which information they forget. Forgetting in this task appears to be mediated by intentional control of memory states in which executive control mechanisms suppress unwanted information. Recognition-induced forgetting is another laboratory task in which subjects forget information. Recognizing a target memory induces the forgetting of related items stored in memory. Rather than occurring due to volitional control, recognition-induced forgetting is an incidental by-product of activating items in memory. Here we asked whether intentional directed forgetting or unintentional recognition-induced forgetting is a more robust forgetting effect. While there was a correlation between forgetting effects when the same subjects did both tasks, the magnitude of recognition-induced forgetting was larger than the magnitude of directed forgetting. These results point to practical differences in forgetting outcomes between two commonly used laboratory-forgetting paradigms.

Indirect modulation of human visual memory

Conditions in which memories become maladaptive have inspired extensive research geared to modulate memory by targeting it directly and explicitly. Given limitations of direct memory modulation, we asked the following: can the target memories be modulated indirectly? To address this question, we uniquely targeted visual memories, and leveraged a paradigm utilizing instructions to either forget or remember newly encoded memories. We used a multi-domain approach, and applied the instructions to embedded verbal information presented during encoding (words), with the intention to indirectly modulate recognition of the target visual context memory itself (pictures). Accordingly, participants were presented with two lists of words, where each word was preceded and followed by pictures. Participants were instructed to either remember or forget the first list of words. As expected, the instruction to either remember or forget the words differentially influenced word memory strength. Importantly, the instruction regarding the words, indirectly modulated picture memory strength. Better memory for words resulted in reduced picture memory strength and vice versa, with the instruction to remember the words reducing picture memory strength. Together with a negative correlation between word and picture memory strength, the results suggest a competition for shared resources between memory for content and context. These findings may open new avenues to indirectly modulate maladaptive memories.

What can directed forgetting tell us about clinical populations?

This paper reviews and critically assesses the implications of directed forgetting (DF) research on clinical populations. We begin by reviewing the typical methods and results of the item method and list method directed forgetting procedures and provide best practice recommendations for future studies using clinical populations. Next, we note that DF was often interpreted as being due to inhibition, and when clinical populations showed impaired directed forgetting, it was treated as evidence in inhibitory control difficulties. However, inhibition may not be the cause of DF effects, based on current understanding of these cognitive tasks. We instead suggest that item method DF is tied to attentional control, which might include inhibitory mechanisms (or might not). In contrast, list method DF is tied to two forms of memory control: control of mental context (indicated by effective forgetting of List 1), and changes in the strategies used to remember (indicated by better learning of List 2). We review the current state of the clinical DF literature, assess its strength based on our best practice recommendations, and call for more research when warranted.

Active Forgetting: Adaptation of Memory by Prefrontal Control

Over the past century, psychologists have discussed whether forgetting might arise from active mechanisms that promote memory loss to achieve various functions, such as minimizing errors, facilitating learning, or regulating one's emotional state. The past decade has witnessed a great expansion in knowledge about the brain mechanisms underlying active forgetting in its varying forms. A core discovery concerns the role of the prefrontal cortex in exerting top-down control over mnemonic activity in the hippocampus and other brain structures, often via inhibitory control. New findings reveal that such processes not only induce forgetting of specific memories but also can suppress the operation of mnemonic processes more broadly, triggering windows of anterograde and retrograde amnesia in healthy people. Recent work extends active forgetting to nonhuman animals, presaging the development of a multilevel mechanistic account that spans the cognitive, systems, network, and even cellular levels. This work reveals how organisms adapt their memories to their cognitive and emotional goals and has implications for understanding vulnerability to psychiatric disorders.

Does Amount of Pre-cue Encoding Modulate Selective List Method Directed Forgetting?

Prior work reported evidence that when people are presented with both a relatively short list of relevant information and a relatively short list of irrelevant information, a subsequent cue to forget the irrelevant list can induce successful selective directed forgetting of the irrelevant list without any forgetting of the relevant list. The goal of the present study is to determine whether this selectivity effect is restricted to short lists of information (six items per list), or if the effect generalizes to longer lists (12 items per list). In Experiment 1, we replicate the finding that selective directed forgetting can occur when short lists of relevant and irrelevant information are involved. Going beyond this replication, we show in Experiment 2 that such selectivity can arise both when shorter and when relatively long lists of items are used. The results are consistent with the view that selective directed forgetting can result from the action of a flexible inhibitory mechanism. They are less well in line with the view that selective cues to forget pre-cue information induce a change in participants' mental context.

Electrophysiological correlates of interference control at retrieval predict performance on a subsequent analogical reasoning task

Previous research has shown that variations in the accessibility of relevant information that stem from retrieval practice may impair analogical reasoning. In the present study, we sought to examine the neural signatures of inhibitory control during selective retrieval and its effects on a subsequent analogical reasoning task by employing electrophysiological measures. At a behavioral level, we found that selective retrieval of a subset of potential solutions led to impaired performance on the analogy test. ERPs analyses during selective retrieval revealed that (1) the repeated presentation of retrieval cues was associated with decreased amplitudes for the FN400 ERP effect, possibly reflecting reduced reactivation of competitor associates and interference across retrieval attempts; (2) this effect correlated positively with the retrieval-related impairment in analogical reasoning performance. During the analogy test, the production of control solutions (non-affected by prior retrieval practice) was characterized by more positive modulations of anterior frontal and parietal ERPs than the production of unstudied solutions, whereas inhibited solutions elicited similar amplitudes to unstudied solutions. This effect was restricted to the retrieval phase of the analogy where the actual solutions had to be retrieved, but it did not affect the mapping phase where the accessibility status of the possible solutions failed to reveal significant amplitude differences. These findings suggest that control during selective retrieval may lead to the downregulation of competing memory representations and advance our understanding of the neural correlates of analogical thinking.

Inhibitory control and temporal perception in cerebral palsy

Prepotent response inhibition and temporal perception abilities were explored in a sample of individuals with cerebral palsy relative to typically developing peers. The extent to which inhibitory control difficulties might affect temporal processing was also investigated. For this purpose, two inhibitory control tasks and two duration estimation tasks were given to the groups of cerebral palsy and typically developing children. Results showed inhibition and temporal perception problems in the group with cerebral palsy. A relationship was found between inhibition and temporal estimation performances, which indicates that inhibitory control contributes, at least partially, to acquisition of the temporal processing ability.

Retrieval of Emotional Events from Memory

The enhancing effects of emotion on memory have been well documented; emotional events are often more frequently and more vividly remembered than their neutral counterparts. Much of the prior research has emphasized the effects of emotion on encoding processes and the downstream effects of these changes at the time of retrieval. In the current review, we focus specifically on how emotional valence influences retrieval processes, examining how emotion influences the experience of remembering an event at the time of retrieval (retrieval as an end point) as well as how emotion alters the way in which remembering the event affects the underlying memory representation and subsequent retrievals (retrieval as a starting point). We suggest ways in which emotion may augment or interfere with the selective enhancement of particular memory details, using both online and offline processes, and discuss how these effects of emotion may contribute to memory distortions in affective disorders.

Reconsidering unconscious persistence: Suppressing unwanted memories reduces their indirect expression in later thoughts

When we seek to forget unwelcome memories, does the suppressed content still exert an unconscious influence on our thoughts? Although intentionally stopping retrieval of a memory reduces later episodic retention for the suppressed trace, it remains unclear the extent to which suppressed content persists in indirectly influencing mental processes. Here we tested whether inhibitory control processes underlying retrieval suppression alter the influence of a memory's underlying semantic content on later thought. To achieve this, across two experiments, we tested whether suppressing episodic retrieval of to-be-excluded memories reduced the indirect expression of the unwanted content on an apparently unrelated test of problem solving: the remote associates test (RAT). Experiment 1 found that suppressed content was less likely than unsuppressed content to emerge as solutions to RAT problems. Indeed, suppression abolished evidence of conceptual priming, even when participants reported no awareness of the relationship between the memory and the problem solving tasks. Experiment 2 replicated this effect and also found that directing participants to use explicit memory to solve RAT problems eliminated suppression effects. Experiment 2 thus rules out the possibility that suppression effects reflect contamination by covert explicit retrieval strategies. Together, our results indicate that inhibitory control processes underlying retrieval suppression not only disrupt episodic retention, but also reduce the indirect influence of suppressed semantic content during unrelated thought processes. Considered with other recent demonstrations of implicit suppression effects, these findings indicate that historical assumptions about the persisting influence of suppressed thoughts on mental health require closer empirical scrutiny and need to be reconsidered.

Oscillatory EEG Changes During Arithmetic Learning in Children

Most studies have investigated brain activation changes after the course of arithmetic learning, and the question remains whether these changes are detectable during the course of learning, i.e., before memory consolidation. Twenty-four fifth graders solved multiplication problems while ongoing electroencephalography (EEG) was recorded. The arithmetic training revealed reduced errors together with a power increase in theta (4-7 Hz) but not in lower alpha (8-10 Hz) or upper alpha (10-13 Hz) bands. We conclude that increases in theta power subserved a shift from slow, procedural strategies to more efficient, automated procedural and retrieval strategies, which led to more efficient performance.

Emotional Memory in Post-traumatic Stress Disorder: A Systematic PRISMA Review of Controlled Studies

Background: Emotional memory is an adaptive process that improves the memorization of emotional events or stimuli. In Post-Traumatic Stress Disorder (PTSD), emotional memory may be altered, which in turn may affect symptoms. Having a clearer view of the processes of interaction between memory and emotional stimuli in PTSD may improve our knowledge of this disorder, and could create new therapeutic management tools. Thus, we performed a systematic review of the evidence of specific emotional memory in PTSD patients. Method: Following PRISMA guidelines, a systematic review of MEDLINE, PsycInfo, and ScienceDirect was undertaken to identify controlled studies on emotional memory that used cognitive tasks on PTSD patients. The initial research was conducted from June 2017 to July 2017, and search terms included: Post-Traumatic Stress Disorder; PTSD; emotional memory; emotion; emotional; memory; and episodic memory. Results: Eighteen studies reporting on 387 PTSD patients met the eligibility criteria. Among the studies selected, 11 observed specific memory processing in PTSD patients, such as a greater memorization of negative information, or a trend to false recognition of negative information. In addition, attentional and inhibition processing seem to play an important role in emotional memory in PTSD sufferers. Furthermore, other studies that did not find behavioral differences between PTSD and control groups nevertheless showed differences in both specific cerebral activities and neurohormone levels during emotional memory tasks. Conclusion: This review has several limitations, including a limited number of controlled studies, small sample sizes, different tasks and methods. Nevertheless, the results of this systematic review provide interesting information on emotional memory for clinicians and researchers, as they seem to highlight facilitated memory processing for negative information in PTSD patients. This topic needs further controlled studies with sensitive behavioral tasks. Also, future studies may evaluate emotional memory after symptom amelioration.

Long-Term Memory Updating: The Reset-of-Encoding Hypothesis in List-Method Directed Forgetting

People's memory for new information can be enhanced by cuing them to forget older information, as is shown in list-method directed forgetting (LMDF). In this task, people are cued to forget a previously studied list of items (list 1) and to learn a new list of items (list 2) instead. Such cuing typically enhances memory for the list 2 items and reduces memory for the list 1 items, which reflects effective long-term memory updating. This review focuses on the reset-of-encoding (ROE) hypothesis as a theoretical explanation of the list 2 enhancement effect in LMDF. The ROE hypothesis is based on the finding that encoding efficacy typically decreases with number of encoded items and assumes that providing a forget cue after study of some items (e.g., list 1) resets the encoding process and makes encoding of subsequent items (e.g., early list 2 items) as effective as encoding of previously studied (e.g., early list 1) items. The review provides an overview of current evidence for the ROE hypothesis. The evidence arose from recent behavioral, neuroscientific, and modeling studies that examined LMDF on both an item and a list level basis. The findings support the view that ROE plays a critical role for the list 2 enhancement effect in LMDF. Alternative explanations of the effect and the generalizability of ROE to other experimental tasks are discussed.

Sex, age, and sex hormones affect recall of words in a directed forgetting paradigm

During the course of serious discussion, an unexpected interruption may induce forgetting of the original topic of a conversation. Sex, age, and sex hormone levels may affect frequency and extension of forgetting. In a list-method directed forgetting paradigm, subjects have to learn two word lists. After learning list 1, subjects receive either a forget or a remember list 1 cue. When the participants had learned list 2 and completed a distraction task, they were asked to write down as many recalled items as possible, starting either with list 1 or list 2 items. In the present study, 96 naturally cycling women, 60 oral contraceptive users, 56 postmenopausal women, and 41 young men were assigned to one of these different experimental conditions. Forget-cued young subjects recall fewer list 1 items (list 1 forgetting) but more list 2 items (list 2 enhancement) compared with remember-cued subjects. However, forget-cued postmenopausal women showed reduced list 1 forgetting but enhanced list 2 retention. Remember-cued naturally cycling women recalled more list 1 items than oral contraceptive users, young men, and postmenopausal women. In forget-cued follicular women, salivary progesterone correlated positively with recalled list 2 items. Salivary 17β-estradiol did not correlate with recalled list 1 or list 2 items in either remember- or forget-cued young women. However, salivary 17β-estradiol correlated with item recall in remember-cued postmenopausal women. Our findings suggest that sex hormones do not globally modulate verbal memory or forgetting, but selectively affect cue-specific processing. © 2016 Wiley Periodicals, Inc.

Control over interfering memories in eating disorders

INTRODUCTION

Recent studies have suggested that patients suffering from either anorexia nervosa (AN) or bulimia nervosa (BN) exhibit abnormal performance in the ability to control cognitive interference in response selection.

METHOD

We assessed the status of cognitive control in episodic memory by addressing the ability to inhibit interfering memories. To this end, we used the retrieval-practice paradigm, which allows for measuring both the beneficial and the detrimental effects of memory practice. The latter phenomenon, known as retrieval-induced forgetting (RIF), is thought to reflect an adaptive inhibitory mechanism aimed at reducing competition in memory retrieval. Twenty-seven healthy controls and 27 patients suffering from eating disorders (either AN or BN) performed a retrieval-practice paradigm and a control task addressing general reactivity and filled a self-report questionnaire on impulsivity.

RESULTS

No differences between patients and healthy controls were observed for the beneficial effects of practice. The same pattern also emerged for RIF. However, when patients with AN and BN were analyzed separately, a clear dissociation emerged: patients with AN displayed no hint of RIF, whereas patients with BN showed an intact memory suppression performance. No group differences emerged in the control task.

CONCLUSIONS

Our findings suggest a specific impairment in the ability to suppress interfering memories in patients with AN, thus extending current evidence of cognitive control deficits in AN to episodic memory.

Impaired memory for material related to a problem solved prior to encoding: suppression at learning or interference at recall?

Earlier research by the author revealed that material encoded incidentally in a speeded affective classification task and related to the demands of a divergent problem tends to be recalled worse in participants who solved the problem prior to encoding than in participants in the control, no-problem condition. The aim of the present experiment was to replicate this effect with a new, size-comparison orienting task, and to test for possible mechanisms of impaired recall. Participants either solved a problem before the orienting task or not, and classified each item in this task either once or three times. There was a reliable effect of impaired recall of problem-related items in the repetition condition, but not in the no-repetition condition. Solving the problem did not influence repetition priming for these items. These results support an account that attributes the impaired recall to inhibitory processes at learning and speak against a proactive interference explanation. However, they can be also accommodated by an account that refers to inefficient context cues and competitor interference at retrieval.

Frontotemporal function]al connectivity and executive functions contribute to episodic memory performance

The contributions of hemispheric-specific electrophysiology (electroencephalogram or EEG) and independent executive functions (inhibitory control, working memory, cognitive flexibility) to episodic memory performance were examined using abstract paintings. Right hemisphere frontotemporal functional connectivity during encoding and retrieval, measured via EEG alpha coherence, statistically predicted performance on recency but not recognition judgments for the abstract paintings. Theta coherence, however, did not predict performance. Likewise, cognitive flexibility statistically predicted performance on recency judgments, but not recognition. These findings suggest that recognition and recency operate via separate electrophysiological and executive mechanisms.

Retrieval-practice task affects relationship between working memory capacity and retrieval-induced forgetting

Retrieving a subset of items from memory can cause forgetting of other items in memory, a phenomenon referred to as retrieval-induced forgetting (RIF). Individuals who exhibit greater amounts of RIF have been shown to also exhibit superior working memory capacity (WMC) and faster stop-signal reaction times (SSRTs), results which have been interpreted as suggesting that RIF reflects an inhibitory process that is mediated by the processes of executive control. Across four experiments, we sought to further elucidate this issue by manipulating the way in which participants retrieved items during retrieval practice and examining how the resulting effects of forgetting correlated with WMC (Experiments 1-3) and SSRT (Experiment 4). Significant correlations were observed when participants retrieved items from an earlier study phase (within-list retrieval practice), but not when participants generated items from semantic memory (extra-list retrieval practice). These results provide important new insight into the role of executive-control processes in RIF.

Measuring Memory Reactivation With Functional MRI: Implications for Psychological Theory

Environmental cues often remind us of earlier experiences by triggering the reactivation of memories of events past. Recent evidence suggests that memory reactivation can be observed using functional MRI and that distributed pattern analyses can even provide evidence of reactivation on individual trials. The ability to measure memory reactivation offers unique and powerful leverage on theoretical issues of long-standing interest in cognitive psychology, providing a means to address questions that have proven difficult to answer with behavioral data alone. In this article, we consider three instances. First, reactivation measures can indicate whether memory-based inferences (i.e., generalization) arise through the encoding of integrated cross-event representations or through the flexible expression of separable event memories. Second, online measures of memory reactivation may inform theories of forgetting by providing information about when competing memories are reactivated during competitive retrieval situations. Finally, neural reactivation may provide a window onto the role of replay in memory consolidation. The ability to track memory reactivation, including at the individual trial level, provides unique leverage that is not afforded by behavioral measures and thus promises to shed light on such varied topics as generalization, integration, forgetting, and consolidation.

The roles of delay and retroactive interference in retrieval-induced forgetting

When subjects study items from different categories and then repeatedly retrieve some of the items from some of the categories, retrieval practice typically improves recall of the practiced items but impairs recall of related but unpracticed items, relative to control items from unpracticed categories. Here, we report the results of three experiments, in which we examined practiced and unpracticed items' delay-induced forgetting (Exp. 1) and their susceptibility to retroactive interference (Exps. 2 and 3). Control items showed the expected memory impairment after longer delay between practice and test and in the presence of retroactive interference. In contrast, both the practiced and the related unpracticed items showed hardly any forgetting under these conditions. The findings are consistent with the results from recent testing-effect studies, which have reported reduced delay-induced forgetting and reduced susceptibility to interference for retrieval-practiced items, and generalize the results to related unpracticed items. The findings are discussed with respect to the inhibitory and noninhibitory accounts of retrieval-induced forgetting, as well as the possible role of selective segregation processes, which may be induced by retrieval practice.

Examining the costs and benefits of inhibition in memory retrieval

Inhibitory control is thought to serve an adaptive function in controlling behavior, with individual differences predicting variation in numerous cognitive functions. However, inhibition is more properly construed as inducing both benefits and costs to performance. Benefits arise at the point when inhibition prevents expression of an unwanted or contextually inappropriate response; costs arise later, when access to the inhibited representation is required by other processes. Here we illustrate how failure to consider both the costs and benefits of inhibition has generated confusion in the literature on individual differences in cognitive control. Using retrieval-induced forgetting as a model case, we illustrate this by showing that changing the way that retrieval-induced forgetting is measured to allow greater expression of the benefits of inhibition together with the costs can reduce and even reverse the theoretically predicted correlation between motor and memory inhibition. Specifically, we show that when the final test in a retrieval-induced forgetting procedure employs item-specific cues (i.e., category-plus-stem cued recall and item-recognition) that better isolate the lingering costs of inhibition, better motor response inhibition (faster stop-signal reaction times) predicts greater retrieval-induced forgetting. In striking contrast, when the final test is less well controlled, allowing both the costs and benefits of inhibition to contribute, motor response inhibition has the opposite relationship with retrieval-induced forgetting. These findings underscore the importance of considering the correlated costs and benefits problem when studying individual differences in inhibitory control. More generally, they suggest that a shared inhibition mechanism may underlie people's ability to control memories and actions.

Interference resolution in retrieval-induced forgetting: behavioral evidence for a nonmonotonic relationship between interference and forgetting

Retrieving memories renders related memories less accessible. This phenomenon, termed retrieval-induced forgetting (RIF), is thought to be the result of processes that resolve interference during competitive retrieval. In several studies, researchers have manipulated the level of interference to test different theoretical accounts of RIF (e.g., inhibitory vs. noninhibitory). However, the nature of how interference and RIF are related has not been systematically investigated. Here, we introduce a design that allows for assessing interference during competitive retrieval by measuring the recall RTs associated with target recall. Using such a design, we found that RIF occurred only when interference during competitive retrieval reached moderate levels, but not when it was too low or too high. This finding might indicate that low levels of interference do not trigger interference resolution, whereas interference resolution might fail when the interference reaches extremely high levels.

Retrieval-induced forgetting: dynamic effects between retrieval and restudy trials when practice is mixed

Results from numerous previous studies suggest that when subjects study items from different categories and then repeatedly retrieve, or restudy, some of the items from some of the categories, repeated retrieval, but not repeated study, induces forgetting of related unpracticed items. We investigated in two experiments whether such effects of pure retrieval and pure study practice generalize to mixed practice-that is, when retrieval and restudy trials are randomly interleaved within a single experimental block. Experiment 1 employed cued recall; Experiment 2 employed item recognition testing. In both experiments, pure repeated retrieval, but not pure repeated study, caused forgetting of related unpracticed items, which is consistent with the prior work. In contrast, with mixed practice, both retrieval and restudy induced forgetting. Thus, whereas retrieval caused forgetting regardless of practice mode, restudy caused forgetting with mixed practice, but not with pure practice. The finding provides first evidence for dynamic effects between retrieval and restudy trials when practice is mixed. It is consistent with the view that, with mixed practice, subjects engage in more retrieval during restudy trials, so that restudy trials may trigger similar processes as retrieval trials and, thus, induce forgetting of related, not restudied, items.

Neural mechanisms of motivated forgetting

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Motivated forgetting of unwanted memories shapes what we retain of our personal past.

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Motivated forgetting is achieved in part by inhibitory control over encoding or retrieval.

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Prefrontal cortex reduces hippocampal and cortical activity to suppress memories.

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Electrophysiological activity during motivated forgetting implicates active inhibition.

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A neurobiological model of memory control can inform disordered control over memory.

Not all memories are equally welcome in awareness. People limit the time they spend thinking about unpleasant experiences, a process that begins during encoding, but that continues when cues later remind someone of the memory. Here, we review the emerging behavioural and neuroimaging evidence that suppressing awareness of an unwelcome memory, at encoding or retrieval, is achieved by inhibitory control processes mediated by the lateral prefrontal cortex. These mechanisms interact with neural structures that represent experiences in memory, disrupting traces that support retention. Thus, mechanisms engaged to regulate momentary awareness introduce lasting biases in which experiences remain accessible. We argue that theories of forgetting that neglect the motivated control of awareness omit a powerful force shaping the retention of our past.

Later Maturation of the Beneficial Than the Detrimental Effect of Selective Memory Retrieval

In adults, selective memory retrieval can both impair and improve recall of other memories. The study reported here examined whether children also show these two faces of memory retrieval. Employing a variant of the directed-forgetting task, we asked second, fourth, and seventh graders to study a list of target and nontarget words. After study, the participants received a cue to either forget or continue remembering the list. We subsequently asked some participants to recall the nontarget words before we tested their memory for the target words; for the remaining participants, we tested memory only for the target words. Prior retrieval of nontarget words impaired retrieval of to-be-remembered target words, regardless of children’s age. In contrast, prior retrieval of nontarget words improved recall of to-be-forgotten target words in seventh graders, though not in fourth and second graders. These results suggest a developmental dissociation between the two faces of memory retrieval and indicate later maturation of the beneficial effect than of the detrimental effect of selective memory retrieval.

Retrieval-induced forgetting under psychosocial stress: no reduction by delayed stress and beta-adrenergic blockade

Retrieval-induced forgetting (RIF) is the phenomenon that 'retrieval-practice', the repeated retrieval of a subset of initially learned material, can impair the recall of episodically related memories. Previous studies showed that RIF is eliminated when retrieval-practice is carried out under psycho-social stress, anxiety, or in negative mood. However, pharmacological manipulation by hydrocortisone did not eliminate the effect. This study investigated the effect of beta-adrenergic blockade on stress-induced modulations of RIF, addressing possible interactive effects of the glucocorticoid and sympatho-adrenomedullary systems. Participants learned categorized word lists and then received either 60 mg propranolol or a placebo. After 90 min they were exposed to the TSST. A third group did not receive any medication and performed a non-stressful control task with the same timing as the other two groups. Finally, all participants underwent retrieval-practice and final recall. Both TSST groups exhibited a stress-induced increase in cortisol-levels, and the placebo group also exhibited large increases in markers of sympathetic nervous system activity and more psychological distress at the time of retrieval-practice. Although, overall recall was poorer under stress, an overall RIF effect emerged irrespective of group and showed no clear modulation by stress with or without beta-adrenergic blockade. In previous demonstrations of RIF elimination by negative emotion, state induction and retrieval-practice followed very briefly after initial learning. Given that both the previous study of hydrocortisone effects on RIF and the present study used longer delays between learning and retrieval-practice, the possibility that stress effects on retrieval-practice eliminate RIF only relatively briefly after learning is discussed.

Brain systems underlying attentional control and emotional distraction during working memory encoding

Goal-directed behavior requires that cognitive operations can be protected from emotional distraction induced by task-irrelevant emotional stimuli. The brain processes involved in attending to relevant information while filtering out irrelevant information are still largely unknown. To investigate the neural and behavioral underpinnings of attending to task-relevant emotional stimuli while ignoring irrelevant stimuli, we used fMRI to assess brain responses during attentional instructed encoding within an emotional working memory (WM) paradigm. We showed that instructed attention to emotion during WM encoding resulted in enhanced performance, by means of increased memory performance and reduced reaction time, compared to passive viewing. A similar performance benefit was also demonstrated for recognition memory performance, although for positive pictures only. Functional MRI data revealed a network of regions involved in directed attention to emotional information for both positive and negative pictures that included medial and lateral prefrontal cortices, fusiform gyrus, insula, the parahippocampal gyrus, and the amygdala. Moreover, we demonstrate that regions in the striatum, and regions associated with the default-mode network were differentially activated for emotional distraction compared to neutral distraction. Activation in a sub-set of these regions was related to individual differences in WM and recognition memory performance, thus likely contributing to performing the task at an optimal level. The present results provide initial insights into the behavioral and neural consequences of instructed attention and emotional distraction during WM encoding.

Repeated Activation of a CS-US-Contingency Memory Results in Sustained Conditioned Responding

Individuals seem to differ in conditionability, i.e., the ease by which the contingent presentation of two stimuli will lead to a conditioned response. In contemporary learning theory, individual differences in the etiology and maintenance of anxiety disorders are, among others, explained by individual differences in temperamental variables (Mineka and Zinbarg, 2006). One such individual difference variable is how people process a learning experience when the conditioning stimuli are no longer present. Repeatedly thinking about the conditioning experience, as in worry or rumination, might prolong the initial (fear) reactions and as such, might leave certain individuals more vulnerable to developing an anxiety disorder. However, in human conditioning research, relatively little attention has been devoted to the processing of a memory trace after its initial acquisition, despite its potential influences on subsequent performance. Post-acquisition processing can be induced by mental reiteration of a conditioned stimulus-unconditioned stimulus (CS-US)-contingency. Using a human conditioned suppression paradigm, we investigated the effect of repeated activations of a CS-US-contingency memory on the level of conditioned responding at a later test. Results of three experiments showed more sustained responding to a "rehearsed" CS+ as compared to a "non-rehearsed" CS+. Moreover, the second experiment showed no effect of rehearsal when only the CS was rehearsed instead of the CS-US-contingency. The third experiment demonstrated that mental CS-US-rehearsal has the same effect regardless of whether it was cued by the CS and a verbal reference to the US or by a neutral signal, making the rehearsal "purely mental." In sum, it was demonstrated that post-acquisition activation of a CS-US-contingency memory can impact conditioned responding, underlining the importance of post-acquisition processes in conditioning. This might indicate that individuals who are more prone to mentally rehearse information condition more easily.

Forgetting in context: the effects of age, emotion, and social factors on retrieval-induced forgetting

Retrieval-induced forgetting (RIF) refers to the finding that selectively retrieving some information impairs subsequent memory for related but nonretrieved information. This occurs both for the individual doing the remembering (i.e., within-individual retrieval-induced forgetting: WI-RIF), as well as for individuals merely listening to those recollections (i.e., socially shared retrieval-induced forgetting: SS-RIF). In the present study, we examined how the contextual factors of age and emotion independently and interactively affect both WI-RIF and SS-RIF. The results indicated that both WI-RIF and SS-RIF occurred at equivalent levels, both for younger and older adults and for neutral and emotional information. However, we identified a boundary condition to this effect: People only exhibited SS-RIF when the speaker that they were listening to was of the same sex as themselves. Given that participants reported feeling closer to same-sex speakers, this suggests that people co-retrieve more, and therefore exhibit increased SS-RIF, with close others. In everyday life, these RIF effects should influence what information is remembered versus forgotten in individual and collective memories.

Retrieval-induced forgetting of words with negative emotionality

Retrieval of a memory can cause forgetting of other related memories. This phenomenon is known as retrieval-induced forgetting (RIF). Previous studies have shown the results with respect to RIF of negative words were mixed, suggesting that it should be reconsidered. We used a stem-cued recall test to re-examine whether RIF occurs for negative words. A total of 30 undergraduate university students (11 male, 19 female) aged 19-22 years (M = 19.83, SD = 0.75) learned target words with neutral and negative emotionality. They then engaged in retrieval practice for half of the neutral and half of the negative targets by completing a word-fragment recall test. Finally a stem-cued recall test encompassing all studied targets was administered. The results of this test revealed that retrieval practice of neutral words caused forgetting of unpractised neutral words, but retrieval practice of negative words did not induce forgetting of unpractised negative words. We attribute the absence of RIF for negative words to baseline deflation or to integration, which were both generated by the inter-relationships between negative words. Further study is needed to clarify which factor, baseline deflation or integration, mainly influences the lack of RIF of negative words.

Prefrontally driven downregulation of neural synchrony mediates goal-directed forgetting

Neural synchronization between distant cell assemblies is crucial for the formation of new memories. To date, however, it remains unclear whether higher-order brain regions can adaptively regulate neural synchrony to control memory processing in humans. We explored this question in two experiments using a voluntary forgetting task. In the first experiment, we simultaneously recorded electroencephalography along with fMRI. The results show that a reduction in neural synchrony goes hand-in-hand with a BOLD signal increase in the left dorsolateral prefrontal cortex (dlPFC) when participants are cued to forget previously studied information. In the second experiment, we directly stimulated the left dlPFC with repetitive transcranial magnetic stimulation during the same task, and show that such stimulation specifically boosts the behavioral forgetting effect and induces a reduction in neural synchrony. These results suggest that prefrontally driven downregulation of long-range neural synchronization mediates goal-directed forgetting of long-term memories.