Item Memory Research Articles

Impact of memory load on processing diminishes rapidly during retention in a complex span paradigm.

Previous work with complex memory span tasks, in which simple choice decisions are imposed between presentations of to-be-remembered items, shows that these secondary tasks reduce memory span. It is less clear how reconfiguring and maintaining various amounts of information affects decision speeds. We introduced preliminary "lead-in" decisions and postencoding "lead-out" decisions to isolate potential influences of reconfiguration and maintenance on decision speeds. Compared with preliminary lead-in choice responses, the response associated with the first memory item slowed substantially. As the list accumulated, decision responses slowed even more. After presentation of the list was complete, decision responses sped rapidly: within a few seconds, decisions were at least as fast as when remembering a single item. These patterns appeared consistently regardless of differences in list length (4, 5, 6, or 7 to-be-remembered items) and response mode (spoken, selection via mouse). This pattern of findings is inconsistent with the idea that merely holding information in mind conflicts with attention-demanding decision tasks. Instead, it is likely that reconfiguring memory items for responding is the source of conflict between memory and processing in complex span tasks. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

An adaptive perspective on visual working memory distortions.

When holding multiple items in visual working memory, representations of individual items are often attracted to, or repelled from, each other. While this is empirically well-established, existing frameworks do not account for both types of distortions, which appear to be in opposition. Here, we demonstrate that both types of memory distortion may confer functional benefits under different circumstances. When there are many items to remember and subjects are near their capacity to accurately remember each item individually, memories for each item become more similar (attraction). However, when remembering smaller sets of highly similar but discernible items, memory for each item becomes more distinct (repulsion), possibly to support better discrimination. Importantly, this repulsion grows stronger with longer delays, suggesting that it dynamically evolves in memory and is not just a differentiation process that occurs during encoding. Furthermore, both attraction and repulsion occur even in tasks designed to mitigate response bias concerns, suggesting they are genuine changes in memory representations. Together, these results are in line with the theory that attraction biases act to stabilize memory signals by capitalizing on information about an entire group of items, whereas repulsion biases reflect a tradeoff between maintaining accurate but distinct representations. Both biases suggest that human memory systems may sacrifice veridical representations in favor of representations that better support specific behavioral goals. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Object memory is multisensory: Task-irrelevant sounds improve recollection

Hearing a task-irrelevant sound during object encoding can improve visual recognition memory when the sound is object-congruent (e.g., a dog and a bark). However, previous studies have only used binary old/new memory tests, which do not distinguish between recognition based on the recollection of details about the studied event or stimulus familiarity. In the present research, we hypothesized that hearing a task-irrelevant but semantically congruent natural sound at encoding would facilitate the formation of richer memory representations, resulting in increased recollection of details of the encoded event. Experiment 1 replicates previous studies showing that participants were more confident about their memory for items that were initially encoded with a congruent sound compared to an incongruent sound. Experiment 2 suggests that congruent object-sound pairings specifically facilitate recollection and not familiarity-based recognition memory, and Experiment 3 demonstrates that this effect was coupled with more accurate memory for audiovisual congruency of the item and sound from encoding rather than another aspect of the episode. These results suggest that even when congruent sounds are task-irrelevant, they promote formation of multisensory memories and subsequent recollection-based retention. Given the ubiquity of encounters with multisensory objects in our everyday lives, considering their impact on episodic memory is integral to building models of memory that apply to naturalistic settings.

Sex differences in item and associative memory among older adults with amnestic mild cognitive impairment

In older adults without cognitive impairment, women have an advantage over men in verbal memory tests; however, whether women with amnestic mild cognitive impairment (aMCI) exhibit this advantage remains controversial. We evaluated sex-specific differences in older adults with and without aMCI in item and associative verbal memory by using an associative memory task with immediate and delayed recognition conditions. The associations between memory task performances and medial temporal morphometric measures were examined. The study included 49 individuals with aMCI and 55 healthy older adults (HOs). The results revealed that a female advantage in immediate item and delayed associative memory was evident in HOs, and the female advantage in associative memory persisted even after item memory performance was controlled. By contrast, the female advantage was absent in individuals with aMCI; such women had more associative false alarms than men with aMCI. Furthermore, decreases in item memory, associative memory, and cortical thickness in the perirhinal and entorhinal regions in individuals with aMCI versus their sex-matched controls were more prominent in women than in men. The relation between brain structure and associative memory function was evident only for women, indicating that women and men may have different cognitive and neural mechanisms for processing associative memory. These findings support the concept of cognitive reserve in women during normal aging. Accounting for sex differences in verbal memory performance is crucial to improve aMCI identification, particularly for women.

Spatial attention based on 2D location and relative depth order modulates visual working memory in a 3D environment.

The attentional effect on visual working memory (VWM) has been a heated research topic in the past two decades. Studies show that VWM performance for an attended memory item can be improved by cueing its two-dimensional (2D) spatial location during retention. However, few studies have investigated the effect of attentional selection on VWM in a three-dimensional setting, and it remains unknown whether depth information can produce beneficial attentional effects on 2D visual representations similar to 2D spatial information. Here we conducted four experiments, displaying memory items at various stereoscopic depth planes, and examined the retro-cue effects of four types of cues - a cue would either indicate the 2D or depth location of a memory item, and either in the form of physical (directly pointing to a location) or symbolic (numerically mapping onto a location) cues. We found that retro-cue benefits were only observed for cues directly pointing to a 2D location, whereas a null effect was observed for cues directly pointing to a depth location. However, there was a retro-cue effect when cueing the relative depth order, though the effect was weaker than that for cueing the 2D location. The selective effect on VWM based on 2D spatial attention is different from depth-based attention, and the divergence suggests that an object representation is primarily bound with its 2D spatial location, weakly bound with its depth order but not with its metric depth location. This indicates that attentional selection based on memory for depth, particularly metric depth, is ineffective.

Neutral auditory words immediately followed by painful electric shock may show reduced next-day recollection.

In this study, we investigated the effect of experimentally delivered acute pain on memory. Twenty-five participants participated in experimental sessions on consecutive days. The first session involved a categorization task to encourage memory encoding. There were two conditions, presented in randomized order, in which participants listened to a series of words, which were repeated three times. In one condition, one-third of the word items were immediately followed by a painful electrical shock. This word-shock pairing was consistent across repetition and the pain-paired items were presented unpredictably. In the other condition, all word items were not associated with pain. Response times over these repeated presentations were assessed for differences. Explicit memory was tested the following day, employing a Remember-Know assessment of word recognition, with no shocks employed. We found evidence that recollection may be reduced for pain-paired words, as the proportion of correct Remember responses (out of total correct responses) was significantly lower. There were no significant reductions in memory for non-pain items that followed painful stimulation after a period of several seconds. Consistent with the experience of pain consuming working memory resources, we theorize that painful shocks interrupt memory encoding for the immediately preceding experimental items, due to a shift in attention away from the word item.

An examination of task factors that influence the associative memory deficit in aging.

Aging is accompanied by a decline in associative memory, whereas item memory remains relatively stable compared to young adults. This age-related associative deficit is well replicated, but its mechanisms and influencing factors during learning are still largely unclear. In the present study, we examined mediators of the age-related associative deficit, including encoding intentionality, strategy instructions, the timing of the memory test (immediate vs. 24 h delayed) and the material being learned (words vs. pictures) in a within-subject design. Older and younger adults performed seven encoding tasks on word pairs and picture pairs on two consecutive days, followed by item and associative recognition tests. The associative deficit was evident after all encoding tasks. We found no evidence for a difference in the magnitude of the associative deficit between incidental vs. intentional learning conditions. However, there was some evidence for a larger associative memory deficit with pictures versus words when the encoding task was held equal. Sentence generation and interactive imagery instructions in which participants generated their own mediators reduced the magnitude of the associative deficit. However, increased encoding guidance through the provision of mediators did not lead to an alleviation of the deficit, potentially because the specified mediators were implausible or difficult for the older adults to reconcile with prior knowledge. Finally, we found some evidence for a reduced age-related associative deficit with a test delay of 24 h. These results contribute to a better understanding of the factors affecting the relative difficulty of older adults with encoding and retrieving novel associations.

Mutual interference in working memory updating: A hierarchical Bayesian model

We propose a hierarchical Bayesian model for working memory updating. This model accounts for both the accuracy of the responses and the reaction times (RT) in the memory updating paradigm, which is a commonly used paradigm to measure working memory capacity. We adapt a mutual interference model from Oberauer and Kliegl (2006) to explain responses. Oberauer and Kliegl (2006) used a Boltzmann equation framework based on the activation levels of items stored in working memory to quantify the probability of correct response at the final recall step after memory updating. We expand the original framework with a Markov chain structure, so that the model accounts for the probabilities of all possible responses, correct or incorrect, at both the intermediate steps during memory updating and the final recall step after memory updating. We use a Wald diffusion process to characterize RT, where the drift rate parameters are associated with the activation levels of items in working memory. This model allows us to investigate the mechanisms underlying choices and RTs in the memory updating paradigm under a joint theoretical framework. A simulation study shows the effectiveness of this model, and posterior predictive distributions and out-of-sample validations show that this model gives a good account of empirical working memory updating findings. We apply the model to two published data sets. The first data set, from Oberauer and Kliegl (2001), examined age differences in working memory. Results from our model reveal an increased level of mutual interference, less use of memory trace information, and potentially less pre-activation of memorized items in older adults compared to younger adults. The second data set, from De Simoni and von Bastian (2018), investigated transfer effects of working memory training. Results from our model reveal a potential transfer effect in the speed of information accumulation, where training in one working memory task may improve the information processing speed in another.

Unconsciously registered items reduce working memory capacity

The assumption that the contents of consciousness correspond to those of working memory (WM) is challenged by evidence that stimuli masked from awareness can be retained for several seconds (Soto et al., 2011; Bergström & Eriksson, 2015). To assess whether conscious and unconscious items compete in a unitary WM store we conducted an experiment in which some of the memory items in an array were masked from conscious sight using continuous flash suppression (CFS) while others remained visible. After a retention interval, participants decided whether the probed item (either masked or visible) had changed its orientation. Behavioral results indicated that change detection for visible items was significantly impaired when masked items were present, suggesting that masked items either displaced or reduced the precision of visible items in WM. However, change detection for masked items was at chance levels, indicating that these items were not stored. The unsuccessful attempt to encode them may have drawn upon a common pool of attentional resources needed to retain or retrieve visible items. Contralateral Delay Activity, an EEG index of net WM load, failed to temporally localize this interference.

Sleep targets highly connected global and local nodes to aid consolidation of learned graph networks

Much of our long-term knowledge is organised in complex networks. Sleep is thought to be critical for abstracting knowledge and enhancing important item memory for long-term retention. Thus, sleep should aid the development of memory for networks and the abstraction of their structure for efficient storage. However, this remains unknown because past sleep studies have focused on discrete items. Here we explored the impact of sleep (night-sleep/day-wake within-subject paradigm with 25 male participants) on memory for graph-networks where some items were important due to dense local connections (degree centrality) or, independently, important due to greater global connections (closeness/betweenness centrality). A network of 27 planets (nodes) sparsely interconnected by 36 teleporters (edges) was learned via discrete associations without explicit indication of any network structure. Despite equivalent exposure to all connections in the network, we found that memory for the links between items with high local connectivity or high global connectivity were better retained after sleep. These results highlight that sleep has the capacity for strengthening both global and local structure from the world and abstracting over multiple experiences to efficiently form internal networks of knowledge.

Investigating age differences in the influence of joint attention on working memory.

Previous research has demonstrated that older adults make limited use of social cues as compared to younger adults. This has been investigated by testing the influence of gaze cues on attentional processes, with findings showing significantly smaller gaze-cuing effects for older than younger adults. Here, we aimed to investigate whether this would also result in age-related differences in the influence of gaze cues on working memory (WM). We therefore tested the effects of gaze cues from realistic human avatars on working memory across two experiments using dynamic head turns and more subtle eye gaze movements. We compared working memory for items looked at by the cue (congruent), looked away from by the cue (incongruent), and items shown when the cue looked down (neutral). Results demonstrated that for both older and younger adults, gaze cues influenced working memory processes, though there were some important differences related to the nature of the cue. When the cue made a dynamic head turn both younger and older adults showed an equivalent effect of gaze on attention. However, when only the eyes moved, while both the younger and older adults showed an effect of gaze on working memory, there appeared to be a difference in how the participants interpreted the neutral cue, with the older adults appearing to interpret the neutral cues in a similar way to the congruent cues. Overall, we provide important evidence that sharing attention benefits cognition across the life span. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The passive state: A protective mechanism for information in working memory tasks.

Memory representations can be stored in a passive state in a visual working memory (VWM) task. However, it remains unclear whether the representations stored in the passive state are prone to interference and decay. To explore this issue, we asked participants to successively remember two sets of memory items (M1 and M2) in three test manners: a combined test (both M1 and M2 are probed simultaneously), a backward test (probe M2 first and M1 second), or a forward test (probe M1 first and M2 second). We found that the contralateral delay activity (CDA) amplitude after the onset of M2 only tracked M2 independently of M1 in the two separate tests (Experiments 1-3), and the accuracy of M1 was well above chance. These results implied that the M1 representations had been transferred from the online state into the passive state after the onset of M2. Furthermore, the accuracy of M1 (two representations were transferred from the online state into the passive state and retrieved later) in the backward test was worse than M2 (2 representations in the online state throughout) in the backward test (Experiments 1-2), but was comparable to M1 (two representations were transferred from the online state into the passive state and retrieved first) in the forward test (Experiment 2). These results demonstrated that the memory representations were impaired during state switching. Importantly, once the representations had been stored in the passive state, they were robust with little memory loss during latent retention. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

WE-191. Information flows from hippocampus to cortex during replay of verbal working memory items

WE-191. Information flows from hippocampus to cortex during replay of verbal working memory items

Storage in Visual Working Memory Recruits a Content-Independent Pointer System

Past work has shown that storage in working memory elicits stimulus-specific neural activity that tracks the stored content. Here, we present evidence for a distinct class of load-sensitive neural activity that indexes items without representing their contents per se. We recorded electroencephalogram (EEG) activity while adult human subjects stored varying numbers of items in visual working memory. Multivariate analysis of the scalp topography of EEG voltage enabled precise tracking of the number of individuated items stored and robustly predicted individual differences in working memory capacity. Critically, this signature of working memory load generalized across variations in both the type and number of visual features stored about each item, suggesting that it tracked the number of individuated memory representations and not the content of those memories. We hypothesize that these findings reflect the operation of a capacity-limited pointer system that supports on-line storage and attentive tracking.

Attention allocation between item and order information in short-term memory.

In immediate memory for verbal lists, recently it has been shown that participants can choose to carry out encoding that prioritises readiness for an item test at some cost to order information or, conversely, that prioritises readiness for an order test at a cost to item information. Here, we ask whether participants can control attention to items and order in a graded fashion. We examined this issue by manipulating the percentage of order or item test trials participants would receive in a block (for each type of test, 25%, 50%, 75%, or 100% of the trials in a block). Overall, the results revealed that participants were able to allocate their attention in a fine-grained manner that took into account the trial distribution within the block. However, there was a difference between the effects of allocating attention to item versus order. Divided attention, compared with full attention to one attribute, had an asymmetry, such that divided attention impaired order performance more than item performance. The exact point at which this asymmetry could be seen differed between two experiments, which included different item tests (fragment completion vs. free recall). The results suggest a common resource for item and order encoding and/or retention in working memory, which can be voluntarily allocated to different mixtures of these two attributes.

Pharmacologically increased cortisol levels impair recall of associative background context memory in males, but not females

Laboratory studies have consistently shown that stress impairs memory retrieval of individual parts (items) of a memory. The stress-hormone cortisol has been particularly linked to this impairment. However, it is unclear whether cortisol similarly affects the binding of items to associative context information in memory, i.e. the constituents of episodic memory. Here, we examine memory retrieval of item and associative memory under pharmacologically elevated cortisol vs. normal levels. Given that previous studies have indicated potential sex differences in the stress- and cortisol-induced memory modulation, we additionally assessed whether there may be sex differences for the cortisol effect on memory retrieval. Eighty-four female and male participants were tested in a placebo controlled, double-blind between-subject design, assigned to either a cortisol (10 mg hydrocortisone) or a placebo group. Participants of both groups were presented foreground images of negative and neutral valence on different neutral background scenes. Twenty-four hours later, participants’ memory for the images and their associated background scene was tested with a recognition task 20 min after substance administration. Among the 78 participants of both groups included in the final analysis, cortisol levels were higher in the cortisol group in comparison to the placebo group, and female participants had higher cortisol levels after hydrocortisone intake in comparison to male participants. Item memory did not differ between the placebo and cortisol group. In contrast, in males, but not females, associative memory for the background scene of emotional foreground images was lower in the cortisol vs. placebo group. Moreover, the individual cortisol increase during the recognition task was negatively correlated to memory for the background scenes of the emotional foreground images only in male participants of the cortisol group. This study shows that pharmacologically increased cortisol levels distinctly affect associative memory in female and male participants, but have no effect on item memory, indicating a complex interaction for the stress effects on memory.

No evidence that the retro-cue benefit requires reallocation of memory resources

Selective mechanisms allow us to prioritize items held in working memory. Does this reflect reallocation of working memory resources? We examined a critical prediction of this account—that reallocating more resources from one item to another should provide a greater benefit. We used a reward manipulation to create variable allocation of resources. Subsequently, a retro-cue instructed participants to drop a memory item. This retro-cue improved performance for the prioritized items relative to a neutral baseline. However, in contrast to the prevailing reallocation account, we found no difference between dropping a higher versus lower reward item. Importantly, removal of high versus low reward items led to better encoding of subsequently presented items, demonstrating that our reward manipulation was successful. While allocation of resources can influence the encoding and storage of new information into working memory, reallocation does not appear to be essential for selection effects in working memory.

A-196 The Relationship Between Attention and Order Errors in Serial Order Memory

Abstract Objective: To investigate if attentional control (AC) predicts the amount of order errors made within serial memory tasks. We also investigated the relationship between AC and item memory (IM), and the relationship between IM and order memory (OM). Methods: Data were collected from undergraduate students at the University of South Alabama. Participants completed three attentional conflict tasks (Bivalent shape task, Global local task, and Flanker task) and three serial memory tasks (symmetry span, digit span, and reading span). The final sample of 112 participants completed all memory tasks and at least two conflict tasks. Confirmatory factor analysis was used to form an AC latent variable from response time difference scores (congruent versus incongruent trials), and IM and OM variables were formed from item and order errors in the memory tasks. Structural equation modeling was used to test correlations among latent variables. Results: The latent AC factor failed to converge. We ran three structural equation models using each conflict task as a predictor variable for both IM and OM. The relationship between IM and OM was significant in all three models. The only other significant pathway across all three models was the relationship between the Flanker task and IM (β = .278, SE = .105, p = .001). Conclusions: Overall, performance on the three conflict tasks did not directly predict order errors. Flanker task performance did directly predict item errors, thus indirectly predicting the amount of order errors in those same tasks.

Motor engagement enhances incidental memory for task-irrelevant items.

Actions shape what we see and memorize. A previous study suggested the interaction between motor and memory systems by showing that memory encoding for task-irrelevant items was enhanced when presented with motor-response cues. However, in the studies on the attentional boost effect, it has been revealed that detection of the target stimulus can lead to memory enhancement without requiring overt action. Thus, the direct link between the action and memory remains unclear. To exclude the effect of the target detection process as a potential confounder, this study assessed the benefit of action for memory by separating items from the response cue in time. In our pre-registered online experiment (N = 142), participants responded to visual Go cues by pressing a key (i.e., motor task) or counting (i.e., motor-neutral cognitive task) while ignoring No-go cues. In each trial, two task-irrelevant images were sequentially presented after the cue disappearance. After encoding the Go/No-go tasks, participants performed a surprise recognition memory test for those images. Importantly, we quantified the impact of overt execution of the action by comparing memories with and without motor response and the impact of covert motor processes (e.g., preparation and planning of action) by comparing memory between the motor and cognitive tasks. The results showed no memory differences between Go and No-go trials in the motor task. This means that the execution itself was not critical for memory enhancement. However, the memory performance in the motor No-go trials was higher than that in the cognitive No-go trials, only for the items presented away from the cues in time. Therefore, engaging the motor task itself could increase incidental memory for the task-irrelevant items compared to a passive viewing situation. We added empirical evidence on the online interaction between action and memory encoding. These memory advantages could be especially brought in action preparation and planning. We believe this fact may expand our present understanding of everyday memory, such as active learning.

Information flows from hippocampus to auditory cortex during replay of verbal working memory items.

The maintenance of items in working memory (WM) relies on a widespread network of cortical areas and hippocampus where synchronization between electrophysiological recordings reflects functional coupling. We investigated the direction of information flow between auditory cortex and hippocampus while participants heard and then mentally replayed strings of letters in WM by activating their phonological loop. We recorded local field potentials from the hippocampus, reconstructed beamforming sources of scalp EEG, and - additionally in four participants - recorded from subdural cortical electrodes. When analyzing Granger causality, the information flow was from auditory cortex to hippocampus with a peak in the [4 8] Hz range while participants heard the letters. This flow was subsequently reversed during maintenance while participants maintained the letters in memory. The functional interaction between hippocampus and the cortex and the reversal of information flow provide a physiological basis for the encoding of memory items and their active replay during maintenance.