Dissociating refreshing and elaboration and their impacts on memory

Beyond Routine Maintenance: Current Trends in Working Memory Research

Working memory (WM) is an evolving concept. Our understanding of the neural functions that support WM develops iteratively alongside the approaches used to study it, and both can be profoundly shaped by available tools and prevailing theoretical paradigms. Here, the organizers of the 2024 Working Memory Symposium-inspired by this year's meeting-highlight current trends and looming questions in WM research. This review is organized into sections describing (1) ongoing efforts to characterize WM function across sensory modalities, (2) the growing appreciation that WM representations are malleable to context and future actions, (3) the enduring problem of how multiple WM items and features are structured and integrated, and (4) new insights about whether WM shares function with other cognitive processes that have conventionally been considered distinct. This review aims to chronicle where the field is headed and calls attention to issues that are paramount for future research.

Enhancing anticipation control of the posture system in the elderly wearing stroboscopic glasses

BACKGROUND

Stroboscopic vision (SV), known for providing intermittent visual input, has been recently integrated into postural training to improve proprioceptive awareness. This research examined the impact of SV on cortico-posture coupling in older adults, along with the related changes in postural control throughout a spectrum of feedback and feedforward processes.

METHODS

A total of thirty-three adults, averaging 66.1 ± 2.5 years of age, were tasked with maintaining an upright posture on a stabilometer, utilizing either complete or intermittent visual guidance. Stabilogram diffusion analysis (SDA) was employed to assess balance strategies based on postural sway, while phase-amplitude coupling (PAC) between postural fluctuations and scalp EEG provided insights into the associated neural control mechanisms.

RESULTS

SV resulted in significantly increased postural sway as compared with that of full-vision feedback (p < 0.001). SDA results indicated greater critical point displacement (CD) (p < 0.001), short-term diffusion coefficients (Ds) (p < 0.001), and scaling exponents (Hs) (p = 0.014) under SV conditions. PAC analysis revealed that the coupling between the postural fluctuation phase and cortical oscillation amplitude in the theta and alpha bands of the fronto-central area was significantly greater in the SV condition than in the full-vision condition (p < 0.001). Additionally, SV led to increased beta PAC in the frontal and sensorimotor areas compared to that of full vision (p < 0.001), which negatively correlated to SV-dependent changes in open-loop gain (Hs) (p < 0.05).

CONCLUSIONS

SV transitions postural sway towards an open-loop process and influences cortico-posture interactions in older adults, emphasizing a neuromotor adaptation to the uncertainty in feedforward predictions when utilizing intermittent visual feedback.

Decoding Mindfulness With Multivariate Predictive Models

Identifying the brain mechanisms that underlie the salutary effects of mindfulness meditation and related practices is a critical goal of contemplative neuroscience. Here, we suggest that the use of multivariate predictive models represents a promising and powerful methodology that could be better leveraged to pursue this goal. This approach incorporates key principles of multivariate decoding, predictive classification, and model-based analyses, all of which represent a strong departure from conventional brain mapping approaches. We highlight 2 such research strategies-state induction and neuromarker identification-and provide illustrative examples of how these approaches have been used to examine central questions in mindfulness, such as the distinction between internally directed focused attention and mind wandering and the effects of mindfulness interventions on somatic pain and drug-related cravings. We conclude by discussing important issues to be addressed with future research, including key tradeoffs between using a personalized versus population-based approach to predictive modeling.

The role of articulatory rehearsal in short-term false memories during ageing

Recent studies have shown that articulatory rehearsal prevents false memories in working memory tasks in young adults. During ageing, a substantial increase in false memories has been documented in numerous studies. The aim of this study was to investigate the role of rehearsal in the increase of false memories with age. In two experiments, we manipulated the opportunity to use rehearsal in a Brown-Peterson task in which younger (n = 80) and older (n = 70) adults maintained semantically related word lists and reported their maintenance strategies. Both experiments showed that reducing the opportunity to use rehearsal increased false memories and decreased correct recall in both groups. Furthermore, older adults made more false memories and less correct recall than younger adults, and these effects were partially mediated by the number of times participants reported using rehearsal (Experiment 2). These findings suggest that age-related differences in rehearsal use explain differences in working memory task performance.

Towards theoretically understanding how long-term memory semantics can support working memory performance

Working memory is the system that supports the temporary storage and processing of information. It is generally agreed that working memory is a mental workspace, with a combination of resources operating together to maintain information in mind for potential use in thought and action. Theories typically acknowledge the contributions of long-term memory to this system. One particular aspect of long-term memory, namely semantic long-term memory, can effectively supplement or "boost" working memory performance. This may be a relatively automatic process via the semantic properties of the stimuli or more active via strategy development and implementation. However, the precise mechanisms require greater theoretical understanding. In this review of the literature, we critically discuss theoretical models of working memory and their proposed links with long-term memory. We also explore empirical research that contributes to our understanding of the ways in which semantics can support performance of both verbal and visuospatial working memory tasks, with a view to potential intervention development. This includes the possibility of training people with lower performance (e.g., older adults) to use semantics during working memory tasks. We conclude that semantics may offer an opportunity to maximise working memory performance. However, to realise this potential, more research is needed, particularly in the visuospatial domain.

Drawing as an efficient encoding tool in younger but not always older adults: The case of associative memory

Episodic memory strongly declines in healthy aging, at least partly because of reduced abilities to create and remember associations (associative memory) and to use efficient memory strategies. Several studies have shown that drawing the to-be-remembered material is a reliable encoding tool to enhance memory of individual items (item memory) because it simultaneously integrates elaborative, pictorial, and motoric processes. These processes in isolation can enhance associative memory in older adults. Nevertheless, their simultaneous impact on associative memory has never been investigated in drawing as an encoding tool. We aimed to investigate whether drawing as an encoding tool not only enhances item memory, but whether its benefit extends to associative memory in younger and older adults. Therefore, we tested 101 older and 100 younger participants in two online experiments and one in-person experiment. Using a memory task for unrelated word-pairs, we compared relational drawing and repeatedly writing (non-relational) as encoding tools and assessed immediate recognition memory of items and associations. In Experiment 2, we additionally assessed recognition memory after 1 week. The findings were consistent across the three experiments: while younger participants benefited from drawing over writing in item and associative memory, older participants benefited in item but not in associative memory. The observed effects remained after 1 week. Thus, we could extend the benefit of drawing to relational drawing in associative memory in younger adults. The lack of benefit in older adults' associative memory might be explained by age-related difficulties in benefiting from memory strategies, and in creating and retrieving associations.

Does the extension of free time trigger spontaneous elaborative strategies in working memory?

Elaboration has emerged as a potential maintenance mechanism involved in the substantial contribution of long-term memory (LTM) to working memory (WM) performance. The objective of the current study was to determine whether elaborative strategies could be spontaneously implemented under favorable conditions. Across four experiments, the distribution of free-time periods was manipulated in a complex span task, while keeping the total amount of free time and cognitive load constant. As elaboration requires time to be set up, Experiment 1 elicited better WM performance in a condition with fewer long free-time periods compared to a condition with many short free-time periods. However, because this benefit did not persist during delayed recall, the following experiments aimed to further investigate this effect by manipulating factors supposed to modulate elaboration. In Experiment 2, half of the participants received no specific instructions regarding strategies whereas the other half were encouraged to use elaborative strategies. In Experiment 3, the to-be-maintained stimuli did or did not have LTM representations that are essential for elaboration (i.e., words or pseudowords). Finally, the last experiment used a self-strategy report to better understand the nature of the WM maintenance strategies spontaneously employed by participants. Despite a consistent effect of free time manipulation on WM recall, the explanatory assumption of elaboration was challenged by the unexpected lack of effect on LTM recall and on the type of strategy reported. Alternative explanations stemming from well-known factors influencing WM performance are discussed, and emphasis is placed on the potential contribution of direct semantic maintenance in WM.

I remember it now, so I'll remember it later: Working memory strength guides predictions for long-term memory performance

Judgments of learning (JOLs) are assumed to be made inferentially, based on cues. This cue-utilization approach substituted the theory that memory strength guides JOLs. The rejection of this theory ignores the existence of two memory systems: working memory (WM), which holds representations immediately accessible, and long-term memory (LTM), which is a permanent store. By manipulating and measuring WM strength, we tested a revised version of the memory-strength theory in which JOLs are guided by WM representations. In Experiment 1, participants memorized sequences of two or four colored objects, then they provided JOLs for an LTM test of these objects, and performed a WM test on the objects' colors. After learning 200 objects, the LTM test followed. Sequence-length affected WM, but not LTM performance. JOLs, however, were higher for sequences of two than for four objects and correlated higher with WM than LTM performance. We replicated these results with a simultaneous presentation of the objects (Experiment 2), in the absence of a WM test (Experiment 3), and in a word-pair task (Experiment 4). Overall, our findings are consistent with the revised memory-strength theory. WM strength should therefore be considered when examining the factors guiding JOLs.

Secondary task engagement drives the McCabe effect in long-term memory

Processing that occurs while information is held in working memory is critical in long-term retention of that information. One counterintuitive finding is that the concurrent processing required during complex span tasks typically impairs immediate memory, while also leading to improved delayed memory. One proposed mechanism for this effect is retrieval practice that occurs each time memory items are displaced to allow for concurrent processing during complex span tasks. Other research has instead suggested that increased free time during complex span procedures underlies this effect. In the present study, we presented participants with memory items in simple, complex, and slow span tasks and compared their performance on immediate and delayed memory tests. We found that how much a participant engaged with the secondary task of the complex span task corresponded with how strongly they exhibited a complex span boost on delayed memory performance. We also probed what participants were thinking about during the task, and found that participants' focus varied depending both on task type and secondary task engagement. The results support repeated retrieval as a key mechanism in the relationship between working memory processing and long-term retention. Further, the present study highlights the importance of variation in individual cognitive processing in predicting long-term outcomes even when objective conditions remain unchanged.

Active maintenance in working memory reinforces bindings for future retrieval from episodic long-term memory

Many theories assume that actively maintaining information in working memory (WM) predicts its retention in episodic long-term memory (LTM), as revealed by the beneficial effects of more WM time. In four experiments, we examined whether affording more time for intentional WM maintenance does indeed drive LTM. Sequences of four words were presented during trials of simple span (short time), slow span (long time), and complex span (long time with distraction; Experiments 1-2). Long time intervals entailed a pause of equivalent duration between the words that presented a blank screen (slow span) or an arithmetic problem to read aloud and solve (complex span). In Experiments 1-3, participants either serially recalled the words (intentional encoding) or completed a no-recall task (incidental encoding). In Experiment 4, all participants were instructed to intentionally encode the words, with the trials randomly ending in the serial-recall or no-recall task. To ensure similar processing of the words between encoding groups, participants silently decided whether each word was a living or nonliving thing via key press (i.e., an animacy judgment; Experiments 1 and 3-4) or read the words aloud and then pressed the space bar (Experiment 2). A surprise delayed memory test at the end of the experiment assessed LTM. Applying Bayesian cognitive models to disambiguate binding and item memory revealed consistent benefits of free time to binding memory that were specific to intentional encoding in WM. This suggests that time spent intentionally keeping information in WM is special for LTM because WM is a system that maintains bindings.

An overview of the hallmarks of cognitive aging

Although the notion of cognitive aging is commonly associated with decline in popular culture, a wealth of scientific literature shows that cognitive aging is more aptly characterized as multidirectional, such that trajectories of cognitive changes include areas of stability and growth (e.g., general knowledge) in addition to decline (e.g., episodic long-term memory). This article overviews these multidirectional trajectories, the heterogeneous factors that moderate the rate of change across individual trajectories, and the extensive literature that has investigated the most important factors, such as working memory, that constrain cognition across the adult lifespan. In light of the multidirectional nature of cognitive change, increasing research has considered methods to leverage the often-overlooked benefits of getting older to ameliorate cognitive deficits.

Self-reported strategy use in working memory tasks

Mnemonic strategies can facilitate working memory performance, but our knowledge on strategy use as a function of task characteristics remains limited. We examined self-reported strategy use in several working memory tasks with pretest data from two large-scale online training experiments. A three-level measure of strategy sophistication (no strategy, maintenance, manipulation) was coded based on participants' open-ended strategy reports. A considerable portion of participants reported some memory strategy, and strategy sophistication was associated with objective task performance. We found a consistent effect of stimulus type: verbal stimuli (letters or digits) elicited higher strategy sophistication than nonverbal ones (colours or spatial positions). In contrast, the association between task paradigm and strategy sophistication was less consistent in the two experiments. The present results highlight the importance of self-generated strategies in understanding individual differences in working memory performance and the role of stimulus characteristics as one of the task-related determinants of strategy use.

Attentional Refreshing in the Absence of Long-Term Memory Content: Role of Short-Term and Long-Term Consolidation

Contradictory results in the literature suggest that attentional refreshing can seemingly not operate efficiently in the absence of semantic representations, while at the same time it does not rely directly on retrieval from semantic memory. The objective of the present study was a better understanding of the bidirectional links between working memory (WM) and long-term memory (LTM), by assessing on the one hand the role of WM mechanisms in long-term recall and on the other hand how their functioning is modulated by the prior LTM content. Through two experiments, we investigated a new hypothesis: attentional refreshing requires stable WM representations independently of the presence or the absence of associated LTM traces. We manipulated this stability through short-term consolidation (Experiment 1) and multiple presentations of memoranda (Experiment 2) to evaluate how it would affect maintenance of words and pseudowords. While we found that lexicality, short-term consolidation and multiple presentations affected short-term and long-term recall, both experiments converged on the conclusion that none of these factors modulated the effect of the cognitive load of the concurrent processing task, suggesting that refreshing does not depend on LTM content nor WM representations' stability. Additionally, we found that delayed recall performance was not affected by the cognitive load, in contradiction with previous literature. These results provide new insight into the functioning of refreshing and the links between WM and LTM.

Examining the relationship between working memory consolidation and long-term consolidation

An emerging area of research is focused on the relationship between working memory and long-term memory and the likely overlap between these processes. Of particular interest is how some information first maintained in working memory is retained for longer periods and eventually preserved in long-term memory. The process of stabilizing transient memory representations for lasting retention is referred to as consolidation in both the working memory and long-term memory literature, although these have historically been viewed as independent constructs. The present review aims to investigate the relationship between working memory consolidation and long-term memory consolidation, which both have rich, but distinct, histories. This review provides an overview of the proposed models and neural mechanisms of both types of consolidation, as well as clinical findings related to consolidation and potential approaches for the manipulation of consolidation. Finally, two hypotheses are proposed to explain the relationship between working memory consolidation and long-term memory consolidation.

Reactivated Visual Masks Do Not Disrupt Serial Recall

The process of spontaneous refreshing plays a central role in current models of working memory but is yet to be observed directly. In a recent study, Rey, Versace, and Plancher (2018) introduced a novel approach to investigate the mechanisms underlying refreshing: They presented tones previously associated with a visual mask during the free time of a complex span task and found that this impaired memory, presumably because reactivation of the masks disrupts refreshing. Here, we aimed to replicate their finding under more controlled settings with more observations per participant. We failed to replicate the previous findings, thereby questioning the robustness of the original effect.

How fast can people refresh and rehearse information in working memory?

Refreshing - briefly attending to an item in working memory - has been proposed as a domain-general maintenance process. According to the time-based resource-sharing (TBRS) theory, people refresh the contents of working memory sequentially at high speed. We measured the speed of refreshing by asking participants to sequentially refresh a small set of items in sync with a metronome, and to adjust the metronome to the fastest speed at which they could refresh. Refreshing speeds converged on about 0.2 s per item for several verbal and visual materials. This time was shorter than the speed of articulatory rehearsal measured with the same method, and - in contrast to rehearsal - did not depend on word length. We sought evidence for people refreshing in sync with the metronome by presenting recognition probes at unpredictable times. We expected that probes matching the just-refreshed item should be recognized faster and more accurately than probes matching other items. This was not the case. A parallel experiment with overt articulatory rehearsal showed poor synchronization of rehearsal with the metronome, suggesting by analogy that refreshing was equally out of sync. The results support the assumption that people can attend sequentially to items in working memory, and monitor this process. This refreshing process is probably faster than rehearsal, but it is unlikely to be as fast as the refreshing process assumed in the TBRS theory.

No Evidence That Articulatory Rehearsal Improves Complex Span Performance

It is usually assumed that articulatory rehearsal improves verbal working memory. Complex span is the most used paradigm to assess working memory functioning; yet, we still lack knowledge about how participants rehearse in this task, and whether these rehearsals are beneficial. In Experiment 1, we investigated the patterns of naturally occurring overt rehearsals in a complex span task requiring processing of a non-verbal distractor task. For comparison, another group of participants completed a matched simple span task with an unfilled delay in between the memoranda. Time permitting, participants rehearsed the memory list in forward serial order, a strategy known as cumulative rehearsal. The degree of cumulative rehearsal was correlated with recall accuracy in both span tasks. Rehearsal frequency was, however, reduced in complex span compared to simple span. To assess the causal role of rehearsal in complex span, we trained a group of participants in a cumulative rehearsal strategy in Experiment 2. This instruction substantially increased the prevalence of cumulative rehearsals compared to a control group. However, the increase in cumulative rehearsal did not translate into an increase in recall accuracy. Our results provide further evidence that rehearsal does not benefit working memory performance.

Distinguishing the Impact of Age on Semantic and Nonsemantic Associations in Episodic Memory

Objectives

Refreshing, or the act of briefly foregrounding recently presented but now perceptually absent representations, has been identified as a possible source of age differences in working memory and episodic memory. We investigated whether the refreshing deficit contributes to the well-known age-related deficit for retrieving nonsemantic associations, but has no impact on existing semantic associations.

Method

Younger and older adults judged the relatedness of stimulus word pairs (e.g., pink–blue or pink–cop) after repeating or refreshing one of the words. During a later source recognition memory test, participants determined whether each item recognized as old was presented on the left or right (nonsemantic source memory) and presented in a related or unrelated pair (semantic source memory). The data were analyzed using a hierarchical Bayesian implementation of a multinomial model of multidimensional source memory.

Results

Neither age group exhibited a refreshing benefit to nonsemantic or semantic source memory parameters. There was a large age difference in nonsemantic source memory, but no age difference in semantic source memory.

Discussion

The study suggests that the nature of the association is most important to episodic memory performance in older age, irrespective of refreshing, such that source memory is unimpaired for semantically meaningful information.