Selective interference with image retention and generation: Evidence for the workspace model

We address three types of model of the relationship between working memory (WM) and long-term memory (LTM): (a) the gateway model, in which WM acts as a gateway between perceptual input and LTM; (b) the unitary model, in which WM is seen as the currently activated areas of LTM; and (c) the workspace model, in which perceptual input activates LTM, and WM acts as a separate workspace for processing and temporary retention of these activated traces. Predictions of these models were tested, focusing on visuospatial working memory and using dual-task methodology to combine two main tasks (visual short-term retention and image generation) with two interference tasks (irrelevant pictures and spatial tapping). The pictures selectively disrupted performance on the generation task, whereas the tapping selectively interfered with the retention task. Results are consistent with the predictions of the workspace model.     

无关长时记忆表征能否引导视觉注意选择?

与任务相关的长时记忆表征在引导视觉注意选择的过程中扮演着重要的角色,它可以使人们在熟悉的视觉情境中快速搜索目标刺激,并偏离干扰刺激。但当长时记忆表征与任务无关时,还能否引导视觉注意选择?目前还不清楚。实验1采用眼动追踪技术直接比较无关工作记忆表征与无关长时记忆表征在视觉搜索阶段对视觉注意的捕获效应,行为反应时与首次注视点百分率的结果都发现,当无关工作记忆表征在视觉搜索中再次出现时能引导视觉注意偏向到与之匹配的干扰刺激,但无关长时记忆表征并没有表现出类似的注意引导效应;实验2探讨记忆表征由工作记忆系统转移到长时记忆系统的过程中对视觉注意的引导效应,结果发现,随着记忆表征的转移,注意引导效应消失了,实验3排除工作记忆表征的干扰后,依然没有发现无关长时记忆表征对注意的引导效应。以上结果表明,无关长时记忆表征并不能像工作记忆表征一样引导视觉注意选择,工作记忆表征和长时记忆表征对视觉注意的引导属于两个不同的认知过程。     

Working memory maintenance contributes to long-term memory formation: Evidence from slow event-related brain potentials

Behavioral research has led to conflicting views regarding the relationship between working memory (WM) maintenance and long-term memory (LTM) formation. We used slow event-related brain potentials to investigate the degree to which neural activity during WM maintenance is associated with successful LTM formation. Participants performed a WM task with objects and letter strings, followed by a surprise LTM test. Slow potentials were found to be more negative over the parietal and occipital cortex for objects and over the left frontal cortex for letter strings during WM maintenance. Within each category, they were enhanced for items that were subsequently successfully remembered. These effects were topographically distinct, with maximum effects at those electrodes that showed the maximum negativity during WM maintenance in general. Together, these results are strongly consistent with the ideas that WM maintenance contributes to LTM formation and that this may occur through strengthening of stimulus-specific cortical memory traces.     

Creation of visual long-term memory

Currently, it is not known by which mechanisms novel visual representations are stored in long-term memory (LTM). Here we report evidence that visual working memory (WM) plays an important role in the formation of visual LTM. By varying exposure times and perceptual difficulty of the stimuli, we find that the rate-limiting factor constraining storage in LTM is the amount of information that can be simultaneously kept in WM, whereas the time needed to store this information into LTM is constant irrespective of the size of the WM content. These results support the hypothesis that visual WM serves as a gate for the storage of information into LTM.     

A processing approach to the working memory/long-term memory distinction: evidence from the levels-of-processing span task

Recent theories suggest that performance on working memory (WM) tasks involves retrieval from long-term memory (LTM). To examine whether WM and LTM tests have common principles, Craik and Tulving's (1975) levels-of-processing paradigm, which is known to affect LTM, was administered as a WM task: Participants made uppercase, rhyme, or category-membership judgments about words, and immediate recall of the words was required after every 3 or 8 processing judgments. In Experiment 1, immediate recall did not demonstrate a levels-of-processing effect, but a subsequent LTM test (delayed recognition) of the same words did show a benefit of deeper processing. Experiment 2 showed that surprise immediate recall of 8-item lists did demonstrate a levels-of-processing effect, however. A processing account of the conditions in which levels-of-processing effects are and are not found in WM tasks was advanced, suggesting that the extent to which levels-of-processing effects are similar between WM and LTM tests largely depends on the amount of disruption to active maintenance processes.     

Neural substrates of successful working memory and long-term memory formation in a relational spatial memory task

Working memory (WM) tasks may involve brain activation actually implicated in long-term memory (LTM). In order to disentangle these two memory systems, we employed a combined WM/LTM task, using a spatial relational (object-location) memory paradigm and analyzed which brain areas were associated with successful performance for either task using fMRI. Critically, we corrected for the performance on the respective memory task when analyzing subsequent memory effects. The WM task consisted of a delayed-match-to-sample task assessed in an MRI scanner. Each trial consisted of an indoor or outdoor scene in which the exact configuration of four objects had to be remembered. After a short delay (7–13 s), the scene was presented from a different angle and spatial recognition for two objects was tested. After scanning, participants received an unexpected subsequent recognition memory (LTM) task, where the two previously unprobed objects were tested. Brain activity during encoding, delay phase and probe phase was analyzed based on WM and LTM performance. Results showed that successful WM performance, when corrected for LTM performance, was associated with greater activation in the inferior frontal gyrus and left fusiform gyrus during the early stage of the maintenance phase. A correct decision during the WM probe was accompanied by greater activation in a wide network, including bilateral hippocampus, right superior parietal gyrus and bilateral insula. No voxels exhibited supra-threshold activity during the encoding phase, and we did not find any differential activity for correct versus incorrect trials in the WM task when comparing LTM correct versus LTM incorrect trials.     

工作记忆和长时记忆共享信息表征的ERP证据

工作记忆和长时记忆共享记忆系统的信息表征网络, 关系密切。实验采用事件相关电位技术记录长时记忆信息对工作记忆的长时语义启动和工作记忆对相关长时记忆信息的长时语义启动。结果显示：与新项目相比, 学习项(即长时记忆信息)对工作记忆的目标信息产生了明显的行为启动效应, N2潜伏期、波幅和P3潜伏期也表现出明显的神经启动效应, 即, 学习项比新项目的反应时更短、N2和P3的潜伏期更短、N2更正, 但学习对非记忆项的影响不大; 工作记忆对相关的长时记忆信息也产生了神经启动, 表现在类别比较任务中记忆类信息比其他信息(即, 与工作记忆任务中的信息无关的内容)的N400更正。而且, 这种神经启动也会因刺激重复次数的增多而降低：与新项目相比, 学习项会使与之语义类似信息的N400更负。上述两种长时语义启动的存在及其ERPs的神经启动均为长时记忆和工作记忆使用共同信息表征的观点提供了证据支持。证据还表明, 在工作记忆和长时记忆的相互作用中注意是关键的调节因素。     

Working memory retrieval differences between medial temporal lobe epilepsy patients and controls: A three memory layer approach

Multi-store models of working memory (WM) have given way to more dynamic approaches that conceive WM as an activated subset of long-term memory (LTM). The resulting framework considers that memory representations are governed by a hierarchy of accessibility. The activated part of LTM holds representations in a heightened state of activation, some of which can reach a state of immediate accessibility according to task demands. Recent neuroimaging studies have studied the neural basis of retrieval information with different states of accessibility. It was found that the medial temporal lobe (MTL) was involved in retrieving information within immediate access store and outside this privileged zone. In the current study we further explored the contribution of MTL to WM retrieval by analyzing the consequences of MTL damage to this process considering the state of accessibility of memory representations. The performance of a group of epilepsy patients with left hippocampal sclerosis in a 12-item recognition task was compared with that of a healthy control group. We adopted an embedded model of WM that distinguishes three components: the activated LTM, the region of direct access, and a single-item focus of attention. Groups did not differ when retrieving information from single-item focus, but patients were less accurate retrieving information outside focal attention, either items from LTM or items expected to be in the WM range. Analyses focused on items held in the direct access buffer showed that consequences of MTL damage were modulated by the level of accessibility of memory representations, producing a reduced capacity.     

On the division of working memory and long-term memory and their relation to intelligence: A latent variable approach

The present study examined the extent to which working (WM) and long-term memory (LTM) reflect the same, related, or completely different constructs and how they relate to other cognitive ability constructs. Participants performed various WM, recall, recognition, general fluid (gF) and general crystallized intelligence (gC) measures. Confirmatory factor analyses suggested that the memory measures could be grouped into three separate yet correlated factors (WM, recall, and recognition) and that these factors were strongly related to gF, but were related less so with gC. Furthermore, it was found that the common variance from the three memory factors could be accounted for by a higher-order memory factor which was strongly related to gF, but less so with gC. Finally, structural equation modeling suggested that both the variance common to the WM tasks and the variance common to all the memory tasks accounted for a unique variance in gF. These results are interpreted within an embedded process model of memory and suggest that WM and LTM tasks measure both shared and unique processes, which are important for intelligence.     

Short-term retention of a single word relies on retrieval from long-term memory when both rehearsal and refreshing are disrupted

Many working memory (WM) models propose that the focus of attention (or primary memory) has a capacity limit of one to four items, and therefore, that performance on WM tasks involves retrieving some items from long-term (or secondary) memory (LTM). In the present study, we present evidence suggesting that recall of even one item on a WM task can involve retrieving it from LTM. The WM task required participants to make a deep (living/nonliving) or shallow (“e”/no “e”) level-of-processing (LOP) judgment on one word and to recall the word after a 10-s delay on each trial. During the delay, participants either rehearsed the word or performed an easy or a hard math task. When the to-be-remembered item could be rehearsed, recall was fast and accurate. When it was followed by a math task, recall was slower, error-prone, and benefited from a deeper LOP at encoding, especially for the hard math condition. The authors suggest that a covert-retrieval mechanism may have refreshed the item during easy math, and that the hard math condition shows that even a single item cannot be reliably held in WM during a sufficiently distracting task—therefore, recalling the item involved retrieving it from LTM. Additionally, performance on a final free recall (LTM) test was better for items recalled following math than following rehearsal, suggesting that initial recall following math involved elaborative retrieval from LTM, whereas rehearsal did not. The authors suggest that the extent to which performance on WM tasks involves retrieval from LTM depends on the amounts of disruption to both rehearsal and covert-retrieval/refreshing maintenance mechanisms.     

Modulation of working, short- and long-term memory by nicotinic receptors in the basolateral amygdala in rats

Male Wistar rats were exposed to one-trial step-down inhibitory avoidance training using a 0.5 mA footshock. Through bilaterally implanted indwelling cannulae, they received bilateral 0.5 microL infusions of saline, mecamylamine (1.0 or 10.0 microg/side), or nicotine (0.6 or 3.0 microg/side) into the basolateral complex of the amygdaloid nucleus (BLA). Infusions were either 10 min before training (Experiment 1) or 4 min after training (Experiment 2). In Experiment 1, the animals were tested three times: first for working memory (WM) 5 s after training, then for short-term memory (STM) 90 min later, and finally for long-term memory (LTM) 24 h later. Mecamylamine depressed and nicotine enhanced WM, STM, and LTM. In Experiment 2, the treatments were given after WM was presumably over. Again, mecamylamine inhibited and nicotine enhanced STM and LTM. The results indicate that nAChRs in BLA participate in the regulation of WM formation and STM and LTM acquisition and consolidation.     

Why do we move our eyes while trying to remember? The relationship between non-visual gaze patterns and memory

Non-visual gaze patterns (NVGPs) involve saccades and fixations that spontaneously occur in cognitive activities that are not ostensibly visual. While reasons for their appearance remain obscure, convergent empirical evidence suggests that NVGPs change according to processing requirements of tasks. We examined NVPGs in tasks with long-term memory (LTM) and working memory (WM) requirements. Experiment 1 yielded significantly higher eye movement rate (EMR) in tasks requiring LTM search than in a WM task requiring maintenance of information. Experiment 2 manipulated accessibility of items in study-test episodic tasks using the levels of processing paradigm. EMR was high in episodic recall irrespective of item accessibility. Experiment 3 examined functional significance of saccades in LTM tasks. Voluntary saccadic suppression produced no evidence that saccades contribute to task performance. We discuss the apparent epiphenomenal nature of spontaneous saccades from an evolutionary perspective and outline a neuroanatomical model of the link between the saccadic and memory system.     

Eye gaze influences working memory for happy but not angry faces

Previous research has shown that angry and happy faces are perceived as less emotionally intense when shown with averted versus direct gaze. Other work reports that long-term memory (LTM) for angry (but not happy) faces was poorer when they were encoded with averted versus direct gaze, suggesting that threat signals are diluted when eye contact is not engaged. The current study examined whether gaze modulates working memory (WM) for angry and happy faces. In stark contrast to LTM effects, WM for angry faces was not significantly modulated by gaze direction. However, WM for happy faces was significantly enhanced when gaze was averted versus direct. These findings suggest that in WM – when rapid processing and an immediate response is required – averted gaze may alter the meaning behind a smile, and make this kind of expression particularly salient for short-term processing.     

Media multitasking and memory: Differences in working memory and long-term memory

Increasing access to media in the 21st century has led to a rapid rise in the prevalence of media multitasking (simultaneous use of multiple media streams). Such behavior is associated with various cognitive differences, such as difficulty filtering distracting information and increased trait impulsivity. Given the rise in media multitasking by children, adolescents, and adults, a full understanding of the cognitive profile of media multitaskers is imperative. Here we investigated the relationship between chronic media multitasking and working memory (WM) and long-term memory (LTM) performance. Four key findings are reported (1) heavy media multitaskers (HMMs) exhibited lower WM performance, regardless of whether external distraction was present or absent; (2) lower performance on multiple WM tasks predicted lower LTM performance; (3) media multitasking-related differences in memory reflected differences in discriminability rather than decision bias; and (4) attentional impulsivity correlated with media multitasking behavior and reduced WM performance. These findings suggest that chronic media multitasking is associated with a wider attentional scope/higher attentional impulsivity, which may allow goal-irrelevant information to compete with goal-relevant information. As a consequence, heavy media multitaskers are able to hold fewer or less precise goal-relevant representations in WM. HMMs’ wider attentional scope, combined with their diminished WM performance, propagates forward to yield lower LTM performance. As such, chronic media multitasking is associated with a reduced ability to draw on the past—be it very recent or more remote—to inform present behavior.     

The amygdala is involved in the modulation of long-term memory, but not in working or short-term memory

Rats with cannulae implanted in the junction between the central and the basolateral nuclei of the amygdala were trained in one-trial step-down inhibitory avoidance and tested at 3 s for working memory (WM) or 1.5 or 24 h later for short-term memory (STM) and long-term memory (LTM), respectively. Several drugs were infused 6 min prior to training in the animals in which WM was measured or 0 min posttraining in those in which STM and LTM were measured: the glutamate receptor antagonists CNQX (0.5 microg) and AP5 (5.0 microg), the indirect GABA A receptor antagonist picrotoxin (0.08 microg), the cholinergic muscarinic receptor blocker scopolamine (2. 0 microg), norepinephrine (0.3 microg), the protein kinase C inhibitor staurosporin (1.0 microg), or the calcium/calmodulin dependent protein kinase II inhibitor Kn-62 (3.5 ng). None of the drugs had any effect on either WM or STM. All had, as previously shown, strong effects on LTM: picrotoxin and norepinephrine enhanced it, and CNQX, AP5, scopolamine, Kn-62, and staurosporin inhibited it. The results do not support the idea that memory of this task is formed in the amygdala; they indicate that the amygdala is not involved in WM or STM processing and support the idea that the amygdala modulates LTM storage processes carried out elsewhere.     

Mathematical problem solving and working memory in children with learning disabilities: both executive and phonological processes are important

The purpose of this investigation was to explore the relationship between working memory (WM) and mathematical problem solving in children with learning disabilities (LD). Children with LD (age 11.5 years) were compared to chronologically age-matched (CA-M) and younger comprehension/computation achievement-matched children (age 8.9 years) on measures of verbal and visual-spatial WM, phonological processing, components of problem solving, and word-problem solving accuracy. The results showed that (1) children with LD were inferior on measures of word solution accuracy, components of problem solving, phonological processing, domain-general WM, and verbal WM when compared to children who were CA-M, (2) children with LD were comparable to younger children on all processing measures, except measures of domain-general WM, visual-spatial WM, phonemic deletion, and identifying problem goals, (3) measures of verbal and visual-spatial WM contributed significant variance to solution accuracy independent of phonological processing, and (4) the influence of WM on solution accuracy was mediated by long-term memory (LTM) processes related to the knowledge of algorithms. The results support the notion that information activated from LTM, rather than phonological processing, mediates the relationship between executive processing and solution accuracy in children with LD.     

Differences in memory functioning between children with attention-deficit/hyperactivity disorder and/or focal epilepsy

Prior research has shown that attention-deficit/hyperactivity disorder (ADHD) and epilepsy are frequently comorbid and that both disorders are associated with various attention and memory problems. Nonetheless, limited research has been conducted comparing the two disorders in one sample to determine unique versus shared deficits. Hence, we investigated differences in working memory (WM) and short-term and delayed recall between children with ADHD, focal epilepsy of mixed foci, comorbid ADHD/epilepsy and controls. Participants were compared on the Core subtests and the Picture Locations subtest of the Children’s Memory Scale (CMS). Results indicated that children with ADHD displayed intact verbal WM and long-term memory (LTM), as well as intact performance on most aspects of short-term memory (STM). They performed worse than controls on Numbers Forward and Picture Locations, suggesting problems with focused attention and simple span for visual-spatial material. Conversely, children with epilepsy displayed poor focused attention and STM regardless of the modality assessed, which affected encoding into LTM. The only loss over time was found for passages (Stories). WM was intact. Children with comorbid ADHD/epilepsy displayed focused attention and STM/LTM problems consistent with both disorders, having the lowest scores across the four groups. Hence, focused attention and visual-spatial span appear to be affected in both disorders, whereas additional STM/encoding problems are specific to epilepsy. Children with comorbid ADHD/epilepsy have deficits consistent with both disorders, with slight additive effects. This study suggests that attention and memory testing should be a regular part of the evaluation of children with epilepsy and ADHD.     

Control of the contents of working memory--a comparison of two paradigms and two age groups

Two experiments investigated whether young and old adults can temporarily remove information from a capacity-limited central component of working memory (WM) into another component, the activated part of long-term memory (LTM). Experiment 1 used a modified Sternberg recognition task (S. Sternberg, 1969); Experiment 2 used an arithmetic memory-updating task. In both paradigms, participants memorized 2 lists, one of which was cued as temporarily irrelevant. Removal of the irrelevant list from capacity-limited WM was indexed by the disappearance of list-length effects of that list on latencies for concurrent processing tasks. Young adults could outsource the irrelevant list within 2-3 s and retrieve it back into the central part of WM later. Old adults showed the same flexibility in the arithmetic updating task but seemed somewhat less able or inclined to temporarily move information into the activated part of LTM in the modified Sternberg task.     

Toward a generalized theory of the shift to retrieval in cognitive skill learning

Prior research on cognitive skill learning has shown that algorithmic and direct memory retrieval strategies are not executed in parallel if the algorithm entails a series of long-term memory (LTM) retrieval steps (as in the case, for example, of mental arithmetic). This phenomenon has been hypothesized to reflect a bottleneck in LTM retrieval processes that forces a strategy choice during an early stage of processing. Here, we investigate simple perceptual–motor algorithms that involve no memory retrieval steps, a largely unexplored case in which parallel strategy execution models remain viable. Pronounced strategy interference was again observed, albeit interference that was different in important respects from that observed for LTM retrieval algorithms. It appears that neither parallel nor choice models, as developed to date, are sufficient as a generalized theory of this skill learning phenomenon. Issues central to the development of a more comprehensive theory are discussed.     

Effects of facial expression on working memory

In long‐term memory (LTM) emotional content may both enhance and impair memory, however, disagreement remains whether emotional content exerts different effects on the ability to maintain and manipulate information over short intervals. Using a working‐memory (WM) recognition task requiring the monitoring of faces displaying facial expressions of emotion, participants judged each face as identical (target) or not (non‐target) to that presented 2 trials back (2‐back). Negative expression was better and faster recognised, illustrated by higher target discriminability and target detection. Positive and negative expressions also induced a more liberal detection bias compared with neutral. Taking the preceding item into account, additional accuracy impairment (negative preceding negative target) and enhancement effects (negative or positive preceding neutral target) appeared. This illustrates a differential modulation of WM based on the affective tone of the target (mirroring LTM enhancement‐ and recognition bias effects), and of the preceding item (enhanced and impaired target detection).