Memory, Sleep, and Dreaming: Experiencing Consolidation

“Compatible with this observation is the proposal that sleep functions to transformmemory traces in part by slowly interleaving neural representations of recent experience into existing remote and semantic cortical networks.(38,69) For example, in their influential article in Psychological Review, McCelland and colleag…”

“Second, a prominent feature of memory reactivation in rodent models is that, within NREM sleep, the strength of neural-level memory replay decays quickly across time.(26,27) Similarly, it seems that sleep mentation may be most strongly related to recent memories early in the sleep phase,(24,28,29) with this associatio…”

“While research on the “default” mode of brain function has brought attention to the importance of spontaneous brain activity occurring during periods of rest and sleep [70,71], surprisingly, virtually none of this work has examined participants' own reports of what is going through their mind at rest.”

“In recent years, an accumulating body of research evidence has definitively demonstrated that post-learning 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].”

“Neuronal firing sequences established during wake are reexpressed only intermittently during rodent NREM sleep, with low fidelity and on a faster timescale than the original experience.(30,31) Similarly, only intermittent fragments of recent episodicmemories appear in sleep mentation, intermingled with remote and sema…”

“In contrast, only a single study has reported similar reactivation of memory during REM sleep.(39) Our recent work examining the effects of learning tasks on sleep mentation have thus focused on periods of stage 1 and 2 NREM sleep immediately after sleep onset.”

“Yet despite widespread theoretical agreement that sleep-dependent memory processing may relate to dream experience [30,36–40,72], attempts to empirically address this hypothesis have been conspicuously absent.”

“In recent years, an accumulating body of research evidence has definitively demonstrated that post-learning 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].”

“To the contrary, recent studies have shown that sleep is important for such complex processes as the integration of new information into established cortical memory networks,(15,16) the extraction of meaning,(17) and the development of insight.(18) Recent studies by Dumay and Gaskell(16) and Tamminen and colleagues(15…”

“While research on the “default” mode of brain function has brought attention to the importance of spontaneous brain activity occurring during periods of rest and sleep [70,71], surprisingly, virtually none of this work has examined participants' own reports of what is going through their mind at rest.”

“Neuronal firing sequences established during wake are reexpressed only intermittently during rodent NREM sleep, with low fidelity and on a faster timescale than the original experience.(30,31) Similarly, only intermittent fragments of recent episodicmemories appear in sleep mentation, intermingled with remote and sema…”

“This reactivation has most consistently been observed during periods of NREM just after learning, within brief hippocampal “sharp-wave ripple” burst events (SPW-Rs1 [12,13]) (Figure 1A).”

“In collaboration with Robert Van de Castle, Calvin Hall pioneered the use of content analysis methods to quantitatively assess the content of large sets of mentation reports [52].”

“These low levels of acetylcholine during NREM sleep have been hypothesized to facilitate the offline consolidation of hippocampus-dependent memory [34], during a time at which recent episodic memories are most likely to be appearing in concomitant dream experience [24,29].”

“In direct support of this hypothesis, a recent study has shown that the extent of neural pattern reactivation after learning predicts subsequent gains in memory performance.(14) Human”

“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, procedural skill learning, emotional memory,(8,9) and spatial navigation.(10,11) Memories of recent experience appea…”

“Furthermore, when animals are exposed to 2 successive spatial experiences, reactivation of both patterns seems to be instantiated simultaneously during subsequent NREM sleep.(26) Compatible with this observation is the proposal that sleep functions to transformmemory traces in part by slowly interleaving neural repres…”

“In recent years, an accumulating body of research evidence has definitively demonstrated that post-learning 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].”

“This reactivation has most consistently been observed during periods of NREM just after learning, within brief hippocampal “sharp-wave ripple” burst events (SPW-Rs1 [12,13]) (Figure 1A).”

“This observation that dreams do not veridically replay waking experience has led some to conclude that such mental activity is incompatible with consolidation of memory.(67,68) To the contrary, emerging evidence suggests that the fragmentary form in which waking experience appears in dreams, intermingled with other me…”

“For example, for hippocampus-dependent declarative memories, retrieval-associated activity in the hippocampal complex decreases after sleep, whereas related activation in cortical structures, particularly medial prefrontal areas, increases.(19,20) Such evidence supports models of systems-level declarative memory conso…”

“Yet despite widespread theoretical agreement that sleep-dependent memory processing may relate to dream experience [30,36–40,72], attempts to empirically address this hypothesis have been conspicuously absent.”

“To the contrary, recent studies have demonstrated, that sleep is important for such complex processes as the integration of new information into established cortical memory networks [17,18], the extraction of meaning [16], and the development of insight [15].”

“For example, the following illustrates a sleep onset dream report that clearly incorporates fragments of a waking experience, but without replicating the original context in which these fragments were embedded (data from Ref.32).”

“In recent years, an accumulating body of research evidence has definitively demonstrated that post-learning 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].”

“In recent years, an accumulating body of research evidence has definitively demonstrated that post-learning 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].”

“For example, for hippocampus-dependent declarative memories, retrievalassociated activity in the hippocampal complex decreases following sleep, while related activation in cortical structures, particularly medial prefrontal areas, increases [19,20].”

“Sleep preferentially benefited (false) memory for these gist words, suggesting that one function of sleep-dependent memory processing is to extract meaningful generalities from large collections of related memories.(17) These and other recent studies suggest that sleep functions not simply to strengthen memories, but…”

“Work from our own laboratory using engaging video game learning tasks has shown that incidence of direct, unambiguous incorporation of task-related imagery at sleep onset declines linearly as a function of time since the initiation of sleep.(28,29) On a broader timescale, it seems that recent life events are most like…”

“Recent work from our own laboratory has provided direct evidence that incorporation of a learning task into subsequent dream experience predicts enhanced sleep-dependent memory consolidation.(66) In this study, participants were trained on a three-dimensional style virtual maze task (Fig.”

“Other functional magnetic resonance imaging (fMRI) studies have described an analogous sleep-dependent reorganization of emotional memory, such that medial prefrontal structures becomemore engaged at delayed retrieval when participants have been allowed to sleep immediately after encoding, in concert with increased re…”

“This observation that dreams do not veridically replay waking experience has led some to conclude that such mental activity is incompatible with consolidation of memory.(67,68) To the contrary, emerging evidence suggests that the fragmentary form in which waking experience appears in dreams, intermingled with other me…”

“Reduced levels of cortisol during early night, SWSdominated sleep have also been hypothesized to both facilitate hippocampal-cortical interactions underlying memory consolidation(35,36) and to promote brain dynamics supporting NREM-type dream experience.(36) Recent papers in sleep and memory have liberally speculated…”

“Other functional magnetic resonance imaging (fMRI) studies have described an analogous sleep-dependent reorganization of emotional memory, such that medial prefrontal structures becomemore engaged at delayed retrieval when participants have been allowed to sleep immediately after encoding, in concert with increased re…”

“Other research has similarly prompted participants to connect dream reports with likely memory sources from waking experience in the previous days and weeks, showing that such memory sources are readily identified with high confidence, and correspond with the ratings of blind judges.(49) We return later to this notion…”

“Hypothesizing that REM sleep dreaming is important for emotional adaptation to stressful events, the work of Rosalind Cartwright has examined dream content as a predictor of psychological outcomes in women after divorce, finding that characteristics of spouserelated dreams predict remission from depression.(76) Other…”

“Other work also supports a role for sleep in emotional adaptation to negative experiences.(77,78) Recent work from our own laboratory has provided direct evidence that incorporation of a learning task into subsequent dream experience predicts enhanced sleep-dependent memory consolidation.”

“Work from our own laboratory using engaging video game learning tasks has shown that incidence of direct, unambiguous incorporation of task-related imagery at sleep onset declines linearly as a function of time since the initiation of sleep.(28,29) On a broader timescale, it seems that recent life events are most like…”

“Compatible with this observation is the proposal that sleep functions to transformmemory traces in part by slowly interleaving neural representations of recent experience into existing remote and semantic cortical networks.(38,69) For example, in their influential article in Psychological Review, McCelland and colleag…”

“These low levels of acetylcholineduring NREM sleep have been hypothesized to facilitate the offline consolidation of hippocampusdependentmemory,(34) duringa timeatwhich recent episodic memories are most likely to be appearing in concomitant dream experience.(24,29) Reduced levels of cortisol during early night, SWSdom…”

“Late-night NREM dreaming can be just as vivid, bizarre, and storylike as the typical dream from REM sleep.(57,60) Yet one consistent difference between dream reports from different stages of sleep seems to be the nature of participant-identified memory sources.”

“Though only a small handful of studies have examined time-of-night effects on incorporation in this manner, both the recency of subject-identified memory sources [61] and the similarity of Wamsley and Stickgold Page 6”

“Other work also supports a role for sleep in emotional adaptation to negative experiences.(77,78) Recent work from our own laboratory has provided direct evidence that incorporation of a learning task into subsequent dream experience predicts enhanced sleep-dependent memory consolidation.”

“Contrary to the entrenched popular belief that “REM sleep = dreaming”, we dream during all stages of sleep [55–58].”

“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, procedural skill learning, emotional memory,(8,9) and spatial navigation.(10,11) Memories of recent experience appea…”

“[48] report that 22% of reports unambiguously incorporated either isolated elements of the laboratory situation (i.”

“memory sources (a hippocampus-dependent form of memory) than are reports from REM sleep,(24) whereas dream experiences from REM sleep are unique in the presence of particularly intense emotions.(25) Second, a prominent feature of memory reactivation in rodent models is that, within NREM sleep, the strength of neural-l…”

“Contrary to the entrenched popular belief that “REM sleep = dreaming”, we dream during all stages of sleep [55–58].”

“Yet despite widespread theoretical agreement that sleep-dependent memory processing may relate to dream experience [30,36–40,72], attempts to empirically address this hypothesis have been conspicuously absent.”

“Late-night NREM dreaming can be just as vivid, bizarre, and storylike as the typical dream from REM sleep.(57,60) Yet one consistent difference between dream reports from different stages of sleep seems to be the nature of participant-identified memory sources.”

“On a broader timescale, it seems that recent life events are most likely to appear in dream content, relative to more remote experiences from years past.(63,64) Several studies also suggest that waking experiences tend to be incorporated into dream mentation either immediately after the experience, or else about a wee…”

“sleep mentation reports to presleep thought [62] have been reported to correlate negatively with time since sleep onset.”

“On a broader timescale, it seems that recent life events are most likely to appear in dream content, relative to more remote experiences from years past.(63,64) Several studies also suggest that waking experiences tend to be incorporated into dream mentation either immediately after the experience, or else about a wee…”

“…a source of creativity, insight and problem-solving (Schredl and Erlacher, 2007), an opportunity for emotional adaptation (Cartwright et al., 1998; Lara-Carrasco et al., 2009), and an expression and potential means of memory consolidation (Nielsen and Stenstrom, 2005; Wamsley and Stickgold, 2011).”

“Some authors even speculate that REM replay may be associated with the vivid dreaming that characterises this sleep stage [67,77].”

“Dreaming could reflect the reactivation and consolidation of memories during sleep (Nielsen and Stenstrom, 2005; Wamsley and Stickgold, 2011).”

“On the neurophysiological level, dream mentation has been suggested to represent the phenomenological reflection of a neural replay of activation patterns associated with recent learning experiences (Wamsley, 2014; Wamsley Stickgold, 2011; Wilson McNaughton, 1994).”