Memory transfer process: an extension of the Sternberg paradigm.

Research conducted by Sternberg (1969) has suggested that there is a transfer process, a cognitive process for activating stored knowledge. His research and that of those who have replicated and extended it have concentrated on distinct declarative lists of information. In two experiments, we have sought to extend this area by studying the cognitive processes for activating an action plan, a sequence of mental operations executed to achieve a goal. Results showed that (a) longer action plans took more time to activate, and (b) when the activation process was interrupted before completion, the process had to be restarted from its beginning after the interruption had been dealt with. These results were interpreted as evidence for a time-consuming transfer process in which the elements of action plans are transferred from long-term store to short-term store. These results are compared with other current data on the transfer process, and implications for the use of controlled knowledge in cognitive tasks are discussed.     

Working Memory: Activation Limitations on Retrieval

Two experiments which require subjects to hold a digit span while solving an equation and then recall the digit span are performed. The size of the memory span and the complexity of the equation are manipulated as well as whether the subject is required to substitute items from the digit span for constants in the equation. As either task (digit span recall or equation solving) gets more complex there are performance decrements (accuracy or latency) not only in that task but also in the other task. It is also shown that the majority of the errors are misretrievals. These results are consistent with the proposal that working memory load has its impact on retrieval from memory. These results are fit by the ACT-R theory (Anderson, 1993) which assumes that there is a limit on source activation and that this activation has to be divided between the two tasks. As either task increases in complexity there is less activation for retrieval of information from declarative memory. Subjects’ misretrievals of associatively related information could be predicted by assuming a partial matching process in ACT-R.     

Working and long-term memory deficits in schizophrenia: is there a common prefrontal mechanism?

This study tested the hypothesis that dorsolateral prefrontal cortex deficits contribute to both working memory and long-term memory disturbances in schizophrenia. It also examined whether such deficits were more severe for verbal than nonverbal stimuli. Functional magnetic resonance imaging was used to assess cortical activation during performance of verbal and nonverbal versions of a working memory task and both encoding and recognition tasks in 38 individuals with schizophrenia and 48 healthy controls. Performance of both working memory and long-term memory tasks revealed disturbed dorsolateral prefrontal cortex activation in schizophrenia, although medial temporal deficits were also present. Some evidence was found for more severe cognitive and functional deficits with verbal than nonverbal stimuli, although these results were mixed.     

Using the memory activation capture (MAC) procedure to investigate the temporal dynamics of hypothesis generation

Research investigating top-down capture has demonstrated a coupling of working memory content with attention and eye movements. By capitalizing on this relationship, we have developed a novel methodology, called the memory activation capture (MAC) procedure, for measuring the dynamics of working memory content supporting complex cognitive tasks (e.g., decision making, problem solving). The MAC procedure employs briefly presented visual arrays containing task-relevant information at critical points in a task. By observing which items are preferentially fixated, we gain a measure of working memory content as the task evolves through time. The efficacy of the MAC procedure was demonstrated in a dynamic hypothesis generation task in which some of its advantages over existing methods for measuring changes in the contents of working memory over time are highlighted. In two experiments, the MAC procedure was able to detect the hypothesis that was retrieved and placed into working memory. Moreover, the results from Experiment 2 suggest a two-stage process following hypothesis retrieval, whereby the hypothesis undergoes a brief period of heightened activation before entering a lower activation state in which it is maintained for output. The results of both experiments are of additional general interest, as they represent the first demonstrations of top-down capture driven by participant-established WM content retrieved from long-term memory.     

努力控制及其神经基础

本文对努力控制的概念、发展及其神经基础进行了归纳和总结。我们发现努力控制涉及的脑区主要包括背外侧和腹外侧前额叶,前扣带回,顶上和顶下小叶以及辅助运动皮层等。此外,通过分析对比后发现努力控制与执行功能之间在行为表现和神经基础上有密切关系：两者都与个体的学业成绩、情绪状态和攻击行为等有关;努力控制涉及的脑区有很大部分处于具有执行功能的突显网络和额顶控制网络。这些证据表明两者之间可能有共同的脑结构基础。     

How activation, entanglement, and searching a semantic network contribute to event memory

Free-association norms indicate that words are organized into semantic/associative neighborhoods within a larger network of words and links that bind the net together. We present evidence indicating that memory for a recent word event can depend on implicitly and simultaneously activating related words in its neighborhood. Processing a word during encoding primes its network representation as a function of the density of the links in its neighborhood. Such priming increases recall and recognition and can have long-lasting effects when the word is processed in working memory. Evidence for this phenomenon is reviewed in extralist-cuing, primed free-association, intralist-cuing, and single-item recognition tasks. The findings also show that when a related word is presented in order to cue the recall of a studied word, the cue activates the target in an array of related words that distract and reduce the probability of the target’s selection. The activation of the semantic network produces priming benefits during encoding, and search costs during retrieval. In extralist cuing, recall is a negative function of cue-to-distractor strength, and a positive function of neighborhood density, cue-to-target strength, and target-to-cue strength. We show how these four measures derived from the network can be combined and used to predict memory performance. These measures play different roles in different tasks, indicating that the contribution of the semantic network varies with the context provided by the task. Finally, we evaluate spreading-activation and quantum-like entanglement explanations for the priming effects produced by neighborhood density.     

Memory by association: Integrating memories prolongs retention by two-year-olds

Recalling one memory often leads to the recollection of other memories that share overlapping features. This phenomenon, spreading activation, was originally documented in studies conducted with verbal adults, and more recently, it has been demonstrated with preverbal infants. Here, we examine the effect of spreading activation on long-term retention by 2-year-olds. Participants were tested in the Visual Recognition Memory (VRM) paradigm and the deferred imitation paradigm. Typically, infants of this age exhibit retention in the VRM paradigm for 24 h, while they exhibit retention in the deferred imitation paradigm for at least 8 weeks. In the present experiment, we paired these tasks together during original encoding and tested infants after an 8-week delay. Two-year-olds exhibited retention in both tasks. That is, when these two tasks initially occurred together – one task that is extremely memorable and one that is not – retrieving the memory of the more memorable task cued retrieval of the less memorable task, extending its longevity.     

Training and transfer effects of long-term memory retrieval training

ABSTRACT

Long-term memory retrieval ability and working memory can share attention control ability. Based on cognitive plasticity, a hypothesis that cognitive training could improve long-term memory retrieval efficiency and that this could transfer to retrieval involving working memory was proposed. 60 undergraduates were randomly assigned to a group of training and an active control group; all the participants completed the same tasks in the same order before and after the training, the tasks included a long-term memory retrieval access task, a intelligence test, a switching task, a working memory updating task, a response inhibition task and an interference control task. The statistics results indicate that cognitive training can improve long-term memory retrieval efficiency and has a transfer effect on working memory updating, interference control and switching ability, but not on response inhibition or intelligence. This reveal the plasticity of long-term memory retrieval and its influence on working memory.     

Memory traces compete under regimes of limited Arc protein synthesis: Implications for memory interference

Recently encoded information can be lost in the presence of new information, a process called 'retrograde interference'. Retrograde interference has been extensively described for more than a century; however, little is known about its underlying mechanisms. Different approaches agree on the need of the synthesis of plasticity related proteins (PRPs) to consolidate a long-term memory (LTM). Our hypothesis is that when PRPs are limited, interference of a task over LTM formation of another may be due to the utilization of protein resources common to both tasks. Here, by combining the tasks of inhibitory avoidance (IA) and open field (OF) exploration in rats, we show that memory traces compete for their stabilization if PRPs are limited. As a result, LTM is formed for only one of the tasks with a consequent decrease in the memory for the other. Furthermore, infusing Arc antisense oligonucleotide into the dorsal hippocampus, we found that Arc is necessary for LTM formation of these two types of learning tasks and is one of the PRPs that can be shared between them when animals are trained in both OF and IA. In sum, these findings suggest that under conditions of reduced protein availability, a learning task interferes with LTM formation of another by using the available PRPs.     

Working memory and the control of action: evidence from task switching.

A series of 7 experiments used dual-task methodology to investigate the role of working memory in the operation of a simple action-control plan or program involving regular switching between addition and subtraction. Lists requiring switching were slower than blocked lists and showed 2 concurrent task effects. Demanding executive tasks impaired performance on both blocked and switched lists, whereas articulatory suppression impaired principally the switched condition. Implications for models of task switching and working memory and for the Vygotskian concept of verbal control of action are discussed.     

工作记忆在监控作业情境意识保持中的作用

本研究通过模拟复杂人机系统的监控作业,考察了长时工作记忆与短时工作记忆在情境意识保持中的作用。研究采用模拟的飞行相撞判断任务,通过考察中断任务对情境意识的影响,分析情境意识在记忆中的存储地点,以及保持时间是否会突破1分钟的限制。本研究选择了心理旋转和算式判断两种中断任务。实验结果表明,在问题回答之前的中断阶段,无论施加心理旋转任务,还是施加算式判断任务,无论中断任务的加工负荷与记忆负荷有多高,熟练被试的情境意识始终保持于较高的水平,并没有因受到中断任务的干扰而出现下降。新手被试的情境意识受到心理旋转任务和算式判断任务的显著影响,而且两种任务的执行速度越快、记忆负荷越大,情绪意识水平就越低。本研究结果说明熟练被试可以利用长时工作记忆存储情境意识,新手被试主要利用短时工作记忆存储情境意识。     

Representation and learning in motor action – Bridges between experimental research and cognitive robotics

To gain a better understanding of the functionality of representation and categorization in action and interaction, it is fundamental that researchers understand how movements are represented in long-term memory. It is our position that human motor control requires that our actions be planned and represented in terms of intended perceptual effects and future task demands, and that the individual has a well-structured mental representation of the task so that the movement can be carried out successfully. Basic Action Concepts (BACs) are identified as major building blocks of cognitive representation in long-term memory, which are cognitive tools used to master the functional demands of movement tasks. In this paper, we consider relevant issues in research methodology and present an experimental method that can be used to assess action-relevant representational structures. This method permits us to observe the strong relationship between cognitive representation and performance in manual action. For example, the specific differences in the mental representations of participants are strongly related to skill level, as well as biomechanical and task constraints. We then discuss results from our learning experiments, where we have examined the development and changes in cognitive representation over time. From these experiments we have found that cognitive reference structures include task-specific spatial information, which provides the basis for action control in skilled voluntary movement. We have implemented these results on various robotic platforms. We argue that the insights gained from various experimental approaches in the field of cognitive psychology and motor control enable researchers to explore the possibilities and limitations of artificial control architectures in robot systems. Finally, we argue that this is not a unidirectional process. Researchers from the field of cognitive psychology and motor control can profit from the advances in technological systems, which enhance the understanding of human motor control in skilled voluntary action.     

Sticky plans: Inhibition and binding during serial-task control

Recent evidence suggests substantial response-time costs associated with lag-2 repetitions of tasks within explicitly controlled task sequences [Koch, I., Philipp, A. M., Gade, M. (2006). Chunking in task sequences modulates task inhibition. Psychological Science, 17, 346-350; Schneider, D. W. (2007). Task-set inhibition in chunked task sequences. Psychonomic Bulletin & Review, 14, 970-976], a result that has been interpreted as inhibition of no-longer relevant tasks. Experiments 1-3 confirm much larger lag-2 costs under serial-control than under externally cued conditions, but also show (a) that these costs occur only when sequences contain at least two distinct chunks and (b) that direct lag-2 repetitions are not a necessary condition for their occurrence. This pattern suggests the hypothesis that rather than task-set inhibition, the large lag-2 costs observed in complex sequences, reflect interference resulting from links between positions within a sequential plan and the individual tasks controlled by this plan. The remaining experiments successfully test this hypothesis (Experiment 4), rule out chaining accounts as a potential alternative explanation (Experiment 5), and demonstrate that interference results from information stored in long-term memory rather than working memory (Experiment 6). Implications of these results for an integration of models of serial-order control and serial memory are discussed.     

Levels-of-processing effects in subject-performed tasks

In memory for subject-performed tasks (SPTs), subjects encode a list of simple action phrases (e.g., thumb through a book, knock at the door) by performing these actions during learning. In three experiments, we investigated the size of the levels-of-processing effects in SPTs as compared with those in standard verbal learning tasks (VTs). Subjects under SPT and VT conditions learned lists of action phrases in a surface or a conceptual orienting task. Under both encoding conditions, the subjects recalled fewer items with surface orienting tasks than with conceptual orienting tasks, but the levels-of-processing effects were strongly reduced in the SPT condition. In the SPT condition, items that were encoded in a surface orienting task were still substantially recalled. The items were recalled almost as well as the conceptually encoded items in the VT condition. The distinct reduction of the levels-of-processing effect is caused by the fact that, in SPT encoding even with a verbal surface orienting task, subjects process conceptual information in order to perform the denoted action. We attribute the small conceptual advantage, which remains with SPT despite the conceptual processing for performing, to the fact that items are not as well integrated into memory as they are when conceptual processing is focused on the action component, rather than on the semantic contexts. This lower integration reduces the accessibility of items in the verbal surface task, even with SPT encoding.     

The posterior parietal paradox: Why do functional magnetic resonance imaging and lesion studies on episodic memory produce conflicting results?

Recent functional magnetic resonance imaging (fMRI) studies addressing healthy subjects point towards posterior parietal cortex (PPC) involvement in episodic memory tasks. This is noteworthy, since neuropsychological studies usually do not connect parietal lesions to episodic memory impairments. Therefore an inventory of the possible factors behind this apparent paradox is warranted. This review compared fMRI studies which demonstrated PPC activity in episodic memory tasks, with findings with studies of patients with PPC lesions. A systematic evaluation of possible explanations for the posterior parietal paradox indicates that PPC activation in fMRI studies does not appear to be attributable to confounding cognitive/psychomotor processes, such as button pressing or stimulus processing. What may be of more importance is the extent to which an episodic memory task loads on three closely related cognitive processes: effort and attention, self‐related activity, and scene and image construction. We discuss to what extent these cognitive processes can account for the paradox between lesion and fMRI results. They are strongly intertwined with the episodic memory and may critically determine in how far the PPC plays a role in a given memory task. Future patient studies might profit from specifically taking these cognitive factors into consideration in the task design.     

Brain activation patterns in major depressive disorder and work stress-related long-term sick leave among Swedish females

Deficits in executive functioning and working memory associated with frontal lobe dysfunction are prominent in depression and work-related long-term sick leave (LTSL). This study used functional magnetic resonance imaging (fMRI) to investigate potential differences in brain activation patterns in these conditions. In addition, the function of the hypothalamic-pituitary-adrenal (HPA) axis was examined and compared between groups. Since there is a clear overrepresentation of women in these diagnostic groups, and to ensure a more homogenous sample population, only women were included. To examine the neural correlates of relevant cognitive processes in patients on sick leave >90 days due to work-related LTSL, recently diagnosed patients with major depression Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV criteria, untreated), and healthy controls (n?=?10, each group), a 2-back working memory task and a visual long-term memory task were administered during fMRI scanning. HPA axis functioning was investigated using a diurnal curve of saliva cortisol and a dexamethasone suppression test. Task performance was comparable among the three groups. Multivariate image analysis revealed that both memory tasks engaged a similar brain network in all three groups, including the prefrontal and parietal cortex. During the 2-back task, LTSL patients had significant frontal hypoactivation compared to controls and patients with depression. Saliva cortisol measurements showed a flattening of the diurnal rythmicity in LTSL patients compared to patients with depression and healthy contols. Taken together, these findings indicate that work stress-related LTSL and major depression are dissociable in terms of frontal activation and diurnal cortisol rhythmicity.     

Strategy-dependent changes in memory: Effects on behavior and brain activity

In the present study, an implicit strategy manipulation was used to explore the contribution of memory strategy to brain activation and behavioral performance. Participants were biased to use either a short-term (maintenance-focused) or long-term (retrieval-focused) memory strategy within a single memory task through manipulation of task context. In comparing directly matched trials across the different task contexts, we observed clear changes in both behavioral performance and brain activity across a network of regions located primarily within lateral and medial frontal cortex. These effects of the memory strategy manipulation suggest that when a retrieval-focused strategy is induced, mnemonic processes are preferentially engaged during the encoding period. In contrast, when a maintenance-focused strategy is induced, mnemonic processes are preferentially engaged during the delay and response periods. Taken together, the results imply that covert cognitive strategies play an important role in modulating brain activation and behavior during memory tasks.     

How memory mechanisms are a key component in the guidance of our eye movements: Evidence from the global effect

Investigating eye movements has been a promising approach to uncover the role of visual working memory in early attentional processes. Prior research has already demonstrated that eye movements in search tasks are more easily drawn toward stimuli that show similarities to working memory content, as compared with neutral stimuli. Previous saccade tasks, however, have always required a selection process, thereby automatically recruiting working memory. The present study was an attempt to confirm the role of working memory in oculomotor selection in an unbiased saccade task that rendered memory mechanisms irrelevant. Participants executed a saccade in a display with two elements, without any instruction to aim for one particular element. The results show that when two objects appear simultaneously, a working memory match attracts the first saccade more profoundly than do mismatch objects, an effect that was present throughout the saccade latency distribution. These findings demonstrate that memory plays a fundamental biasing role in the earliest competitive processes in the selection of visual objects, even when working memory is not recruited during selection.     

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.     

Neural correlates of learning and working memory in the primate posterior parietal cortex

The posterior parietal cortex has been traditionally associated with coordinate transformations necessary for interaction with the environment and with visual-spatial attention. More recently, involvement of posterior parietal cortex in other cognitive functions such as working memory and task learning has become evident. Neurophysiological experiments in non-human primates and human imaging studies have revealed neural correlates of memory and learning at the single neuron and at the brain network level. During working memory, posterior parietal neurons continue to discharge and to represent stimuli that are no longer present. This activation resembles the responses of prefrontal neurons, although important differences have been identified in terms of the ability to resist stimulation by distracting stimuli, which is more evident in the prefrontal than the posterior parietal cortex. Posterior parietal neurons also become active during tasks that require the organization of information into larger structured elements and their activity is modulated according to learned context-dependent rules. Neural correlates of learning can be observed in the mean discharge rate and spectral power of neuronal spike trains after training to perform new task sets or rules. These findings demonstrate the importance of posterior parietal cortex in brain networks mediating working memory and learning.