Reactivation and Consolidation of Memory During Sleep

ABSTRACT— Recent research has shown compellingly that sleep supports the consolidation of declarative memories for events and facts. During consolidation, memories are stabilized against future interference and undergo qualitative changes with regard to their "explicitness" and underlying neural representation. In this article, we argue that declarative memory consolidation during sleep is based on covert reactivations of newly encoded memory traces in the hippocampus. During slow-wave sleep (SWS), the prominent slow oscillations act to synchronize the repeated reactivation of the newly encoded representations in hippocampal networks with the generation of spindle activity in the thalamus, supporting changes in neocortical networks that contribute to long-term memory storage. In this view, sleep plays an active role in the consolidation of memories, in which the neuronal reactivation of newly acquired memories is critical for the redistribution and integration of these memories into the network of pre-existing long-term memories.     

Physical attractiveness stereotype and memory

Three experiments examined explicit and implicit memory for information that is congruent with the physical attractiveness stereotype (i.e. attractive-positive and unattractive-negative) and information that is incongruent with the physical attractiveness stereotype (i.e. attractive-negative and unattractive-positive). Measures of explicit recognition sensitivity and implicit discriminability revealed a memorial advantage for congruent compared to incongruent information, as evident from hit and false alarm rates and reaction times, respectively. Measures of explicit memory showed a recognition bias toward congruent compared to incongruent information, where participants tended to call congruent information old, independently of whether the information had been shown previously or not. This recognition bias was unrelated to reports of subjective confidence in retrieval. The present findings shed light on the cognitive mechanisms that might mediate discriminatory behavior towards physically attractive and physically unattractive individuals.     

New approaches to understanding unconscious processes: Implicit and explicit memory systems

Abstract

Freud viewed the unconscious as being roughly equivalent to dynamically repressed wishes, needs, and motivations. Findings from developmental psychology, cognitive psychology, psychoanalysis, and neuroscience over the past 40 years have dramatically changed our views of unconscious processes and the human mind. It is now clear that Freud's dynamic unconscious is only a minor segment of information that is processed at subsymbolic, implicit, and automatic levels. Only a fraction of this information is further processed at explicit conscious levels. Moreover, the vast majority of the information that remains nonconscious is adaptive and has major consequences for development. We examine some clinical implications of these views.     

RASP: A system for the analysis of memory tasks

The purpose of this paper is to introduce a system for the analysis of memory tasks. The system involves four basic task dimensions, derived from an ecological analysis of memory functioning: Reproductivity (R), Acquisition (A), Sufficiency (S), and Productivity (P). Three studies are reported in which professional memory psychologists were asked to rate sets of standard laboratory and more ecologically relevant memory tasks in terms of the four RASP dimensions. In general, results implied independence across the two sets of tasks between the four dimensions. Interrater reliabilities were found to be modest to high. However, it was suggested that RASP best be used as a tool for understanding the meaningful relations that exist among dimensions within general sets or pools of tasks, for different classes of tasks, as well as for prototypical tasks. We argue that, especially when the relationship between RASP profiles for two particular tasks is crossvalidated by behavioral data, and conflict with assumptions about what memory systems or processes are involved, then there is a potential for conceptual refinement. This refinement could be attained either through an increased theoretical generalization, or through an increased theoretical precision. Based on obtained RASP information at the level of classes of tasks (e.g., episodic vs. semantic) as well as at a prototypical task level (e.g., word recall vs. prose recall), several intriguing memory phenomena are discussed. Finally, we suggest that RASP may serve as a tool for reducing the number of task-specific assumptions of what systems and processes mediate memory performance.     

Learning strategy differentially impacts memory connections in children and adults

Even once children can accurately remember their experiences, they nevertheless struggle to use those memories in flexible new ways—as in when drawing inferences. However, it remains an open question as to whether the developmental differences observed during both memory formation and inference itself represent a fundamental limitation on children's learning mechanisms, or rather their deployment of suboptimal strategy. Here, 7–9-year-old children (N = 154) and young adults (N = 130) first formed strong memories for initial (AB) associations and then engaged in one of three learning strategies as they viewed overlapping (BC) pairs. We found that being told to integrate—combine ABC during learning—both significantly improved children's ability to explicitly relate the indirectly associated A and C items during inference and protected the underlying pair memories from forgetting. However, this finding contrasted with implicit evidence for memory-to-memory connections: Adults and children both formed A-C links prior to any knowledge of an inference test—yet for children, such links were most apparent when they were told to simply encode BC, not integrate. Moreover, the accessibility of such implicit links differed between children and adults, with adults using them to make explicit inferences but children only doing so for well-established direct AB pairs. These results suggest that while a lack of integration strategy may explain a large share of the developmental differences in explicit inference, children and adults nevertheless differ in both the circumstances under which they connect interrelated memories and their ability to later leverage those links to inform flexible behaviours.

Research Highlights

• Children and adults view AB and BC pairs related through a shared item, B. This provides an opportunity for learners to connect A–C in memory.
• Being encouraged to integrate ABC during learning boosted performance on an explicit test of A–C connections (children and adults) and protected from forgetting (children).
• Children and adults differed in when implicit A–C connections were formed—occurring primarily when told to separately encode BC (children) versus integrate (adults), respectively.
• Adults used implicit A–C connections to facilitate explicit judgments, while children did not. Our results suggest developmental differences in the learning conditions promoting memory-to-memory connections.

     

Eliciting false memories on implicit and explicit memory tests after incidental learning

Abstract: In a false memory experiment, lists of semantic associates (e.g., newspaper, letter, book, etc.) were presented to three groups of participants to induce false memories for critical nonpresented (CN) words (e.g., read) in an incidental learning task. The control group simply estimated the frequency rate in everyday Japanese discourse of each word on a list. The imagery instruction group received an additional instruction to imagine a thematically related converging word from the target words on a list. Participants in the imagery plus writing group received the same instructions as those in the imagery instruction group, but were also required to write down the word they imagined for each list. The results from the implicit and explicit memory tests given after the incidental learning episode showed that the level of priming for CN words was equivalent to that for actually presented target words for all three groups on the implicit test, whereas explicit memory results showed that participants explicitly recognized more target words than CN words. The implications for implicit associative response and fuzzy‐trace theories of false memory, as well as implicit priming, are discussed.     

奖赏与自我加工对记忆的影响

【摘 要】目的:从外显和内隐层面探讨奖赏与自我加工对记忆的影响。方法：以大学生为被试,以人格形容词为实验材料,采用R/K范式,测量被试对识记词语的记忆效果。结果：（1）外显记忆层面,奖赏与自我加工均促进了记忆效果;（2）在内隐记忆层面,自我存在记忆的加工优势,但是没有发现奖赏加工对记忆的影响。结论：自我相关刺激促进了内隐和外显记忆的加工,奖赏刺激只对外显记忆有影响,实验结果支持独立平行模型,即在不同记忆层面,奖赏加工与自我参照加工存在不同加工机制。     

提取干扰对内隐记忆的影响

以往研究多认同内隐记忆不会受到干扰的影响,但主要集中于编码时的干扰不会影响随后的内隐记忆提取成绩,而对于提取时的干扰是否也不会影响内隐记忆成绩仍存在疑义。该文在实验1采用学习-测验范式,通过在提取阶段设置同时干扰任务进一步考察提取干扰与内隐记忆的关系,结果表明提取干扰下并未发现明显的启动效应,即提取干扰破坏了内隐记忆。为进一步探讨内隐记忆的提取干扰效应是否源于记忆与干扰刺激同时呈现所引起的知觉表征竞争,实验2改变了记忆与干扰刺激的呈现顺序,结果表明不论干扰刺激在记忆项目之前或之后呈现,启动效应均受到影响。相比之下,提取干扰对再认成绩的影响并不明显(实验3)。上述结果表明,内隐记忆的提取干扰效应是源于一般认知资源的竞争,在提取过程中任何能够产生认知资源竞争的变量设置都可能会削减内隐测验中的启动效应。     

Word priming without awareness: A new approach to circumvent explicit memory contamination

A major methodological limitation arising in the experimental study of implicit memory is that tasks that are characterized as implicit memory tests can be seriously contaminated by the use of covert explicit memory strategies. Given the evidence indicating that brief presentation of words (below the awareness threshold of subjects) can produce semantic priming, we wondered whether rapid visual presentation of primed words might provide an avenue to produce word priming without explicit memory contamination. Normal subjects were tested for word priming on a speeded category membership decision task. Explicit or implicit encoding procedures were used in four different experiments. Results demonstrated that brief presentation of words can indeed offer a means of producing word priming in absence of explicit recognition or recall of the primed words presented during the study phase. They also showed that such priming is equivalent in degree to the priming measured when using either a conventional implicit memory design or an explicit encoding procedure prior to the study of the primes.     

睡眠和记忆之间关系的研究

睡眠和记忆是人类重要的功能．人们对于二者之间的关系一直非常感兴趣、本文综述了近年来睡眠和记忆之间关系研究的主要成果,从动物和人的不同角度进行讨论．并进一步综述了近年有关事件相关电位和功能成像等的研究成果．在有关人的探讨中,进一步讨沦了快波睡眠,慢波睡眠、睡眠的组织、睡眠缺失等对记忆的影响、     

REM Sleep Bout Duration and Frequency in PTSD

The few pharmacological treatments shown to be effective in reducing sleep disturbance in posttraumatic stress disorder (PTSD) might work through normalization of rapid eye movement (REM). However, evidence of REM sleep disturbance in PTSD has been inconsistent and the definition of REM bout has varied as well. In this study, we compared polysomnographic findings in adults with PTSD to both normal sleepers and insomniacs. We found no differences between those with and without PTSD on REM bout frequency or duration. We did, however, find gender differences within our PTSD sample as consistent with a previous review suggesting that males with PTSD are more likely to demonstrate REM sleep disturbance. Consensus on REM bout definition is needed, in addition to studies powered to detect gender differences.     

The role of chronic physical exercise and selective attention at encoding on implicit and explicit memory

Despite the evidence revealing benefits of chronic cardiovascular exercise on executive functions, little research has been conducted on long-term memory. We aimed to investigate the effect of physical exercise on implicit and explicit memory when attention was modulated at encoding in two groups of active and sedentary participants. With this purpose, attention was manipulated in a similar way in the implicit and explicit memory tasks by presenting picture outlines of two familiar objects, one in blue and the other in green, and participants were asked to pay attention only to one of them. Implicit memory was assessed through conceptual priming and explicit memory through a free recall task followed by recognition. The results did not reveal significant differences between groups in conceptual priming or free recall. However, in recognition, while both groups had similar discrimination for attended stimuli, active participants showed lower discrimination between unattended and new stimuli. These results suggested that exercise may have effects on specific cognitive processes, that is, that active participants may suppress non-relevant information better than sedentary participants, making the discrimination between unattended and new items more difficult.     

Emotional enhancement of immediate memory: Positive pictorial stimuli are better recognized than neutral or negative pictorial stimuli

We examined emotional memory enhancement (EEM) for negative and positive pictures while manipulating encoding and retrieval conditions. Two groups of 40 participants took part in this study. Both groups performed immediate implicit (categorization task) and explicit (recognition task) retrieval, but for one group the tasks were preceded by incidental encoding and for the other group by intentional encoding. As indicated by the sensitivity index (d'), after incidental encoding positive stimuli were easier to recognize than negative and neutral stimuli. Participants' response criterion was more liberal for negative stimuli than for both positive and neutral ones, independent of encoding condition. In the implicit retrieval task, participants were slower in categorizing positive than negative and neutral stimuli. However, the priming effect was larger for emotional than for neutral stimuli. These results are discussed in the context of the idea that the effect of emotion on immediate memory enhancement may depend on the intentionality to encode and retrieve information.     

精神分裂症患者的记忆损害

摘 要 目的 探讨精神分裂症患者记忆损害状况。方法 采用修正的加工分离记忆实验程序,分别测试精神分裂症患者和正常对照组的记忆能力。结果 （1）精神分裂症患者外显记忆功能存在广泛的缺陷,而内隐记忆功能缺陷只在概念驱动下的测验中出现。（2）以阳性症状为主的精神分裂症患者的外显记忆成绩均高于以阴性症状为主的精神分裂症患者。(3)阴性症状严重程度与外显记忆成绩呈显著负相关。结论 精神分裂症患者的内隐记忆功能相对完整,而外显记忆障碍在以阴性症状为主的精神分裂症患者尤为突出。     

从认知神经的角度看内隐记忆和外显记忆的分离

当前的一些理论观点认为,内隐记忆和外显记忆依赖于两种不同的记忆系统,它们与大脑的不同区域相联系。该文通过回顾以往相关研究,从神经心理学及神经成像两方面对两种记忆系统的分离现象进行概述：在神经心理学领域发现的证据表明内隐记忆在神经解剖上与外显记忆是分离的;使用fMRI和PET技术,研究者观察到与内隐记忆有关的枕颞区及左下前额区中衰减的神经活动,以及与外显记忆有关的内侧颞区、前额皮层和后内侧顶皮层中增强的活动;使用ERP技术,研究也发现了两种记忆神经系统在时空上的不同特征     

内隐和外显记忆的遗忘特点

根据实验性分离范式 ,选定加工分离程序为工具 ,通过对再认的两个加工过程进行的延时比较 ,考察了内隐和外显记忆的遗忘特点。结果显示 :在延时分别为 0、6分钟、15分钟、1小时和 7天的遗忘进程中 ,再认的自动提取和意识性提取成绩表现了不同的特征 ,尤其是在前 15分钟的遗忘进程中 ,自动提取成绩的衰减不明显而意识性提取成绩的衰减非常显著 ,表明内隐记忆和外显记忆具有不同的遗忘特点。另外研究还通过对加工水平因素的考察 ,发现了加工水平因素对意识性提取和自动提取成绩的作用不同。     

Sleep facilitates consolidation of positive emotional memory in healthy older adults

ABSTRACT

Evidence has demonstrated that sleep-related memory consolidation declines in ageing. However, little is known about age-related changes to sleep-related emotional memory consolidation, especially when considering the positivity effect observed in older adults. In the present study, we sought to explore whether there is a positive emotional bias in sleep-related memory consolidation among healthy older adults. Young and older adults were randomly assigned either into a sleep or wake condition. All participants encoded positive, negative, and neutral stimuli and underwent recognition tests immediately (test 1), after a 12-hour sleep/wake interval (test 2), and 3 days after test 2 (test 3). Results showed that age-related differences of sleep beneficial effect were modulated by emotion valence. In particular, sleep selectively enhanced positive memory in older adults, while in young adults sleep beneficial effect was manifested in neutral memory. Moreover, the sleep beneficial effect can be maintained at least 3 days in both young and older adults. These findings suggest that older adults had preserved but positive bias of sleep-related memory consolidation, which could be one of the underlying mechanisms for their generally better emotional well-being in daily life. These findings highlight the dynamic interplay among sleep and emotional memory in older adults.     

Neuroimaging of Priming: New Perspectives on Implicit and Explicit Memory

Priming refers to a change in the ability to identify or produce an item as a consequence of a specific prior encounter. Priming has been studied extensively in cognitive studies of healthy volunteers, neuropsychological investigations of brain-damaged patients, and, more recently, studies using modern functional neuroimaging techniques such as positron emission tomography and functional magnetic resonance imaging. We review recent neuroimaging studies that have converged upon the conclusion that priming is reliably accompanied by decreased activity in a variety of brain regions. The establishment of this cortical signature of priming is beginning to generate new hypotheses concerning the relation between priming and explicit retrieval, which we illustrate by considering recent experiments on within- and cross-modality priming.     

汉字特征内隐学习的初步实验研究

在汉字特征识别的范围内,在高强度练习和正确反馈条件下探讨内隐学习汉字的某些特点。实验采用了一种测量内隐和外显学习的特征分类方法．这些特征包括汉字的笔划维度（显著性特征）和汉字的偏好维度（非显著性特征）。实验结果发现：汉字偏好特征的学习,内隐组被试表现出更大的底层规则的迁移;汉字的偏好特征还表现出高潜力的内隐知识。