The short- and long-term consequences of directed forgetting in a working memory task

Selectively maintaining an object's feature in visual working memory: A comparison between highly discriminable and fine-grained features

Selectively maintaining information is an essential function of visual working memory (VWM). Recent VWM studies have mainly focused on selective maintenance of objects, leaving the mechanisms of selectively maintaining an object's feature in VWM unknown. Based on the interactive model of perception and VWM, we hypothesized that there are distinct selective maintenance mechanisms for objects containing fine-grained features versus objects containing highly discriminable features. To test this hypothesis, we first required participants to memorize a dual-feature object (colored simple shapes vs. colored polygons), and informed them about the target feature via a retro-cue. Then a visual search task was added to examine the fate of the irrelevant feature. The selective maintenance of an object's feature predicted that the irrelevant feature should be removed from the active state of VWM and should not capture attention when presented as a distractor in the visual search task. We found that irrelevant simple shapes impaired performance in the visual search task (Experiment 1). However, irrelevant polygons did not affect visual search performance (Experiment 2), and this could not be explained by decay of polygons (Experiment 3) or by polygons not capturing attention (Experiment 4). These findings suggest that VWM adopts dissociable mechanisms to selectively maintain an object's feature, depending on the feature's perceptual characteristics.

The Trajectory of Targets and Critical Lures in the Deese/Roediger-McDermott Paradigm: A Systematic Review

The Deese/Roediger-McDermott (DRM) paradigm has been used extensively to examine false memory. During the study session, participants learn lists of semantically related items (e.g., pillow, blanket, tired, bed), referred to as targets. Critical lures are items which are also associated with the lists but are intentionally omitted from study (e.g., sleep). At test, when asked to remember targets, participants often report false memories for critical lures. Findings from experiments using the DRM show the ease with which false memories develop in the absence of suggestion or misinformation. Given this, it is important to examine factors which influence the generalizability of the findings. One important factor is the persistence of false memory, or how long false memories last. Therefore, we conducted a systemic review to answer this research question: What is the persistence of false memory for specific items in the DRM paradigm? To help answer this question our review had two research objectives: (1) to examine the trajectory of target memory and false memory for critical lures and (2) to examine whether memory for targets exceeded false memory for critical lures. We included empirical articles which tested memory for the same DRM lists with at least two testing sessions. We discuss the results with respect to single-session delays, long-term memory recall and recognition, remember and know judgments for memory, and the effect of development, valence, warning, and connectivity on the trajectory of memory. Overall, the trajectory of targets showed a relatively consistent pattern of decrease across delay. The trajectory of critical lures was inconsistent. The proportion of targets versus critical lures across delay was also inconsistent. Despite the inconsistencies, we conclude that targets and critical lures have a dissimilar trajectory across delay and that critical lures are more persistent than targets. The findings with respect to long-term recall and recognition are consistent with both Fuzzy Trace Theory and Associative-Activation Theory of the DRM effect. The generation of false memory with brief delays (3-4 s) is better explained by Associative-Activation Theory. Examining the connectivity between target items, and critical lures, and the effect that has during study and retrieval, can provide insight into the persistence of false memory for critical lures.

Failing to forget? Evidence for both impaired and preserved working memory control in older adults

Voluntary forgetting is accomplished via top-down control over memory contents. Age-related declines in cognitive control may compromise voluntary forgetting. Using a working-memory variant of a directed forgetting task, we examined age differences in forgetting efficacy by analyzing direct measures of memory accuracy and two indirect measures of retention: proactive interference and semantic distortions. The directed forgetting effect in long-term memory was virtually absent in older adults. Further, compared to young adults, older adults recognized fewer to-be-remembered and more to-be-forgotten items in working memory. However, indirect measures of forgetting efficacy suggest some spared ability to control working memory contents in older adults: Both young and older adult participants exhibited reduced proactive interference for to-be-forgotten words (Experiment 1) and reduced semantic errors to to-be-forgotten list associates (Experiment 2) in working memory. Indirect memory measures of forgetting efficacy can provide a fuller understanding of spared and impaired control processes in older adults.

The part-list cuing effect in working memory: The influence of task presentation mode

The modulation of part-list cues on long-term memory has been well-documented, whereas its impact on working memory remains largely unknown. The current study recruited a working memory part-list cuing paradigm to investigate how re-exposing part-list items affected item representation in working memory, and more specifically, whether the cuing effect was modulated by the task presentation mode. Our results showed that when the part-list re-exposure and no-part-list re-exposure trials were presented in separate blocks, using the re-exposed items as retrieval cues (part-list cue condition) significantly impaired recognition speed, accuracy and elevated judgement criteria (Experiment 1a), whereas merely relearning the re-exposed items (part-list relearning condition) has no such effect (Experiment 1b). When the part-list cue trials are randomly interleaved with the no-part-list cue trials, recognition accuracy was significantly lower in the part-list cue condition, whereas the recognition speed and judgement criteria were not significantly different under the two conditions (Experiment 2). These results indicate that re-exposing subsets of previously memorized items as retrieval cues can reduce the strength of other representations in working memory. Moreover, the effect of part-list cues in working memory is affected by task presentation mode. The mechanisms of part-list cuing within working memory were discussed.

A Frontal Account of False Alarms

Prior research has demonstrated that the frontal lobes play a critical role in the top-down control of behavior, and damage to the frontal cortex impairs performance on tasks that require executive control [Burgess, P. W., & Stuss, D. T. Fifty years of prefrontal cortex research: Impact on assessment. Journal of the International Neuropsychological Society, 23, 755-767, 2017; Stuss, D. T., & Levine, B. Adult clinical neuropsychology: Lessons from studies of the frontal lobes. Annual Review of Psychology, 53, 401-433, 2002]. Across executive functioning tasks, performance deficits are often quantified as the number of false alarms per total number of nontarget trials. However, most studies of frontal lobe function focus on individual task performance and do not discuss commonalities of errors committed across different tasks. Here, we describe a neurocognitive account that explores the link between deficient frontal lobe function and increased false alarms across an array of experimental tasks from a variety of task domains. We review evidence for heightened false alarms following frontal deficits in episodic long-term memory tests, working memory tasks (e.g., n-back), attentional tasks (e.g., continuous performance tasks), interference control tasks (e.g., recent probes), and inhibitory control tasks (e.g., go/no-go). We examine this relationship via neuroimaging studies, lesion studies, and across age groups and pathologies that impact the pFC, and we propose 11 issues in cognitive processing that can result in false alarms. In our review, some overlapping neural regions were implicated in the regulation of false alarms. Ultimately, however, we find evidence for the fractionation and localization of certain frontal processes related to the commission of specific types of false alarms. We outline avenues for additional research that will enable further delineation of the fractionation of the frontal lobes' regulation of false alarms.

Goal-directed and stimulus-driven selection of internal representations

Adaptive behavior relies on the selection of relevant sensory information from both the external environment and internal memory representations. In understanding external selection, a classic distinction is made between voluntary (goal-directed) and involuntary (stimulus-driven) guidance of attention. We have developed a task-the anti-retrocue task-to separate and examine voluntary and involuntary guidance of attention to internal representations in visual working memory. We show that both voluntary and involuntary factors influence memory performance but do so in distinct ways. Moreover, by tracking gaze biases linked to attentional focusing in memory, we provide direct evidence for an involuntary "retro-capture" effect whereby external stimuli involuntarily trigger the selection of feature-matching internal representations. We show that stimulus-driven and goal-directed influences compete for selection in memory, and that the balance of this competition-as reflected in oculomotor signatures of internal attention-predicts the quality of ensuing memory-guided behavior. Thus, goal-directed and stimulus-driven factors together determine the fate not only of perception, but also of internal representations in working memory.

Serial position-dependent false memory effects

Evidence for false recognition within seconds of encoding suggests that semantic-associative influences are not restricted to long-term memory, consistent with unitary memory accounts but contrary to dual store models. The present study sought further relevant evidence using a modified free recall converging associates task where participants studied 12-item lists composed of 3 semantically distinct quartets (sublists) related to a separate, non-presented theme word (i.e., words 1-4/theme1, 5-8/theme2, and 9-12/theme3). This list construction permits assessment of false recall errors from each sublist, and, particularly, the primacy and recency sublists that have been linked to long- and short-term memory stores. Experiment 1 tested immediate free recall for items. Associative false memories were evident from all sublists, however, significantly less so from the recent sublist, which also showed the highest levels of veridical memory. By inserting a brief (3 s) distractor prior to recall, Experiment 2 selectively reduced veridical memory and increased false memory for the recent sublist while leaving the primacy sublist unaffected. These recall results converge with prior evidence indicating the immediacy of false recognition, and can be understood within a unitary framework where the differential availability of verbatim features and gist-based cues affect memory for primacy and recency sublists.

The removal of information from working memory

What happens to goal-relevant information in working memory after it is no longer needed? Here, we review evidence for a selective removal process that operates on outdated information to limit working memory load and hence facilitates the maintenance of goal-relevant information. Removal alters the representations of irrelevant content so as to reduce access to it, thereby improving access to the remaining relevant content and also facilitating the encoding of new information. Both behavioral and neural evidence support the existence of a removal process that is separate from forgetting due to decay or interference. We discuss the potential mechanisms involved in removal and characterize the time course and duration of the process. In doing so, we propose the existence of two forms of removal: one is temporary, and reversible, which modifies working memory content without impacting content-to-context bindings, and another is permanent, which unbinds the content from its context in working memory (without necessarily impacting long-term forgetting). Finally, we discuss limitations on removal and prescribe conditions for evaluating evidence for or against this process.

The impact of intermediate-term alcohol abstinence on memory retrieval and suppression

Background: The nature of episodic memory deficit in intermediate-term abstinence from alcohol in alcohol dependence (AD) is not yet clarified. Deficits in inhibitory control are commonly reported in substance use disorders. However, much less is known about cognitive control suppressing interference from memory. The Think/No-think (TNT) paradigm is a well established method to investigate inhibition of associative memory retrieval.

Methods: Thirty-six unmedicated patients with AD and 36 healthy controls (HCs) performed the TNT task. Thirty image–word pairs were trained up to a predefined accuracy level. Cued recall was examined in three conditions: Think (T) for items instructed to-be-remembered, No-think (NT) assessing the ability to suppress retrieval and Baseline (B) for general relational memory. Premorbid IQ, clinical variables and impulsivity measures were quantified.

Results: AD patients had a significantly increased demand for training. Baseline memory abilities and effect of practice on retrieval were not markedly different between the groups. We found a significant main effect of group (HC vs. AD) × condition (B, T, and NT) and a significant difference in mean NT–B scores for the two groups.

Discussion: AD and HC groups did not differ essentially in their baseline memory abilities. Also, the instruction to focus on retrieval improved episodic memory performance in both groups. Crucially, control participants were able to suppress relational words in the NT condition supporting the critical effect of cognitive control processes over inhibition of retrieval. In contrast to this, the ability of AD patients to suppress retrieval was found to be impaired.