Memory reactivation and consolidation during sleep (original) (raw)
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Memory, Sleep, and Dreaming: Experiencing Consolidation
Sleep Medicine Clinics, 2011
During all stages of sleep, the mind and brain are working to process new memories, consolidating them into long-term storage and integrating recently acquired information with past experience. In recent years, an accumulating body of research evidence has definitively shown that postlearning sleep is beneficial for human memory performance across a variety of tasks, including verbal learning, 1-4 procedural skill learning, 2,5-7 emotional memory, 8,9 and spatial navigation. 10,11 Memories of recent experience appear nightly in the content of our dreams, and animal research shows that presleep experience is replayed on a cellular level during postlearning sleep. Sleep-dependent memory consolidation has been extensively examined from a variety of behavioral and neuroscientific perspectives, but studies examining dream experience as an indicator of mnemonic activity in the sleeping brain are conspicuously absent. This article reviews evidence that the use of subjective report as a method for probing the activities of the mind and brain is critical for a comprehensive approach to understanding memory consolidation. Recent work suggests that dream experiences recalled from sleep are a direct reflection of concomitant memory processes in the brain.
The role of sleep in declarative memory consolidation: passive, permissive, active or none?
Current Opinion in Neurobiology, 2006
Those inclined to relish in scientific controversy will not be disappointed by the literature on the effects of sleep on memory. Opinions abound. Yet refinements in the experimental study of these complex processes of sleep and memory are bringing this fascinating relationship into sharper focus. A longstanding position contends that sleep passively protects memories by temporarily sheltering them from interference, thus providing precious little benefit for memory. But recent evidence is unmasking a more substantial and long-lasting benefit of sleep for declarative memories. Although the precise causal mechanisms within sleep that result in memory consolidation remain elusive, recent evidence leads us to conclude that unique neurobiological processes within sleep actively enhance declarative memories.
Neuron, 2004
will be covered: (1) early work in this area-a brief history; (2) some important general considerations on this topic; (3) REM sleep deprivation studies in animals; (4) cognitive capacities of humans with greatly suppressed We discuss several lines of evidence refuting the hypothesis that procedural or declarative memories are or absent REM sleep; (5) recent human studies on procedural memory and sleep; (6) the "replay" of patterns of processed/consolidated in sleep. One of the strongest arguments against a role for sleep in declarative mem-neural activity of waking in subsequent sleep in animals; (7) "other factors" that dispute a role for sleep in memory ory involves the demonstration that the marked suppression or elimination of REM sleep in subjects on processing; and (8) a proposed function for sleep. antidepressant drugs or with brainstem lesions produces no detrimental effects on cognition. Procedural A Revisiting of This Issue memory, like declarative memory, undergoes a slow, Although possibly not recognized outside of the sleep time-dependent period of consolidation. A process field, the role of sleep in memory processing is not a has recently been described wherein performance on new issue, but is one that was thoroughly examined in some procedural tasks improves with the mere pasthe 1960s to 1970s. There was a wealth of research in sage of time and has been termed "enhancement." animals, and to a lesser extent in humans, devoted to Some studies, but not others, have reported that the this topic (for review, see McGrath and Cohen, 1978; consolidation/enhancement of perceptual and motor Horne and McGrath, 1984; Smith, 1985; Horne, 1988). skills is dependent on sleep. We suggest that consoli-Current interest represents a second wave. Most of the dation or enhancement, initiated in waking with task early work in this area in both animals and humans acquisition, could in some instances extend to sleep, examined the effects of REM sleep deprivation on prebut sleep would serve no unique role in these proviously learned material. As later discussed in detail, the cesses. In sum, there is no compelling evidence to results of numerous studies on this subject, involving support a relationship between sleep and memory various manipulations across species, were divided. consolidation. There were as many reports that failed to describe a link between sleep and memory as there were those that claimed such a relationship (Horne and McGrath, Born, J., and Gais, S. (2000). REM sleep deprivation: The wrong paradigm leading to wrong conclusions. Behav. Brain Sci. 23, analogous to processes shown for declarative memo-912-913. ries. Consolidation (as stabilization) begins with task Brashers-Krug, T., Shadmehr, R., and Bizzi, E. (1996). Consolidation initiation, and unless disrupted by competing events, in human motor memory. Nature 382, 252-255.
The Role of Memory Reactivation during Wakefulness and Sleep in Determining Which Memories Endure
Consolidation makes it possible for memories of our daily experiences to be stored in an enduring way. We propose that memory consolidation depends on the covert reactivation of previously learned material both during sleep and wakefulness. Here we tested whether the operation of covert memory reactivation influences the fundamental selectivity of memory storage— of all the events we experience each day, which will be retained and which forgotten? We systematically manipulated the value of information learned by 60 young subjects; they learned 72 object-location associations while hearing characteristic object sounds, and a number on each object indicated the reward value that could potentially be earned during a future memory test. Recall accuracy declined to a greater extent for low-value than for high-value associations after either a 90 min nap or a 90 min wake interval. Yet, via targeted memory reactivation of half of the low-value associations using the corresponding sounds, these memories were rescued from forgetting. Only cued associations were rescued when sounds were applied during wakefulness, whereas the entire set of low-value associations was rescued from forgetting when the manipulation occurred during sleep. The benefits accrued from presenting corresponding sounds show that covert reactivation is a major factor determining the selectivity of memory consolidation in these circumstances. By extension, covert reactivation may determine the ultimate fate of our memories, though wake and sleep reactivation might play distinct roles in this process, the former helping to strengthen individual, salient memories, and the latter strengthening, while also linking, categorically related memories together.
Sleep transforms the cerebral trace of declarative memories
Proceedings of The National Academy of Sciences, 2007
After encoding, memory traces are initially fragile and have to be reinforced to become permanent. The initial steps of this process occur at a cellular level within minutes or hours. Besides this rapid synaptic consolidation, systems consolidation occurs within a time frame of days to years. For declarative memory, the latter is presumed to rely on an interaction between different brain regions, in particular the hippocampus and the medial prefrontal cortex (mPFC). Specifically, sleep has been proposed to provide a setting that supports such systems consolidation processes, leading to a transfer and perhaps transformation of memories. Using functional MRI, we show that postlearning sleep enhances hippocampal responses during recall of word pairs 48 h after learning, indicating intrahippocampal memory processing during sleep. At the same time, sleep induces a memory-related functional connectivity between the hippocampus and the mPFC. Six months after learning, memories activated the mPFC more strongly when they were encoded before sleep, showing that sleep leads to longlasting changes in the representation of memories on a systems level.
A Dream Model: Reactivation and Re-encoding Mechanisms for Sleep-dependent Memory Consolidation
Cognitive Science, 2016
We humans spend almost a third of our lives asleep, and there is mounting evidence that sleep not only maintains, but actually improves many of our cognitive functions. Memory consolidation - the process of crystallizing and integrating memories into knowledge and skills - is particularly benefitted by sleep. We survey the evidence that sleep aids memory consolidation in various declarative and implicit memory tasks and review the basic neurophysiological structure of sleep with a focus on understanding what neural systems are involved. Drawing on machine learning research, we discuss why it might be useful for humans–and robots, perhaps–to have such an offline period for processing, even though humans are clearly capable of learning incrementally, online. Finally, we propose and simulate two mechanisms for use in computational memory models to accomplish sleep-based consolidation via either or both 1) re-encoding knowledge representations and 2) reactivating and strengthening recen...
Memory consolidation during sleep involves context reinstatement in humans
SummaryNew memories aren’t quarantined from each other when first encoded; rather, they are interlinked with memories that were encoded in temporal proximity or share semantic features. By selectively biasing memory processing during sleep, here we test whether context influences sleep-consolidation. Participants first formed 18 idiosyncratic narratives, each linking four objects together. Before sleep,they also memorized an on-screen position for each object. During sleep, 12 object-specific sounds were unobtrusively presented, thereby cuing the corresponding spatial memories and impacting spatial recall as a function of initial memory strength. As hypothesized, we find that recall for non-cued objects contextually linked with cued objects also changed. Post-cue electrophysiological responses suggest that activity in the sigma band supports context reinstatement and predicts context-related memory benefits. Concurrently, context-specific electrophysiological activity patterns emerg...
System memory consolidation is conceptualized as an active process whereby newly encoded memory representations are strengthened through selective memory reactivation during sleep. However, our learning experience is highly overlapping in content (i.e., shares common elements), and memories of these events are organized in an intricate network of overlapping associated events. It remains to be explored whether and how selective memory reactivation during sleep has an impact on these overlapping memories acquired during awake time. Here, we test in a group of adult women and men the prediction that selective memory reactivation during sleep entails the reactivation of associated events and that this may lead the brain to adaptively regulate whether these associated memories are strengthened or pruned from memory networks on the basis of their relative associative strength with the shared element. Our findings demonstrate the existence of efficient regulatory neural mechanisms governing how complex memory networks are shaped during sleep as a function of their associative memory strength.
Current Opinion in Behavioral Sciences, 2020
Two vital memory functions-remembering specific experiences and generalizing across many experiences-are in tension with each other. In the complementary-learning-systems model, the hippocampus allows for fast learning of unique episodic memories while the cortex slowly extracts regularities from overlapping representations. Whereas episodic memories undergo consolidation over protracted time periods, many questions remain about how memory generalization evolves over time. Sleep's role in consolidating individual memories has been convincingly demonstrated using targeted memory reactivation, a method whereby memories can be selectively strengthened through the unobtrusive presentation of learning-related stimuli during sleep. In this review, we argue that targeted memory reactivation can help advance understanding of memory transformation and the contrast between specificity and generalization.