Memory and Sleep: How Sleep Cognition Can Change the Waking Mind for the Better

In the paper

“Behavioral studies of memory consolidation during sleep have produced ample evidence of superior retrieval of various types of information after a period of sleep compared to a period of wake (e.g., Karni et al. 1994, Plihal & Born 1997, Walker et al. 2002, Tucker et al. 2006).”

What the sources say

• Not checked yetcites Karni et al. 1994
• Not checked yetcites Plihal & Born 1997
• Not checked yetcites Walker et al. 2002

In the paper

“In keeping with this idea, damage to the medial temporal lobe can lead to a profound impairment in learning, or anterograde amnesia.”

In the paper

“The proposal that human declarative memories undergo consolidation for many months after learning, initially regarded by researchers as surprising, is now widely accepted (Squire 1992, Squire & Wixted 2011).”

What the sources say

• Not checked yetcites Squire 1992
• Not checked yetcites Squire & Wixted 2011

In the paper

“This finding was later extended to show that the temporal patterns of action potentials exhibited during wake are repeated during sleep, constituting memory replay (Skaggs & McNaughton 1996).”

What the sources say

• Not checked yetcites Skaggs & McNaughton 1996

In the paper

“Rodent hippocampal place cells with fields used in recent exploration fired more frequently during sleep compared to cells with fields not encountered during pre-sleep exploration (Pavlides & Winson 1989).”

What the sources say

• Not checked yetcites Pavlides & Winson 1989

In the paper

“In a seminal study on memory consolidation, Wilson & McNaughton (1994) found that coordinated place cell activity in the hippocampus was likely to reoccur again during sleep.”

What the sources say

• Not checked yetcites Wilson & McNaughton 1994

In the paper

“For example, auditory entrainment produced an increase in spindles with characteristics resembling those of endogenous spindles (Antony & Paller 2017).”

What the sources say

• Not checked yetcites Antony & Paller 2017

In the paper

“However, given findings that memory changes after a nap correlated with SWS spindle activity but not with N2 spindle activity (Antony et al. 2012, Cox et al. 2012), spindles during SWS may be particularly important for consolidation.”

What the sources say

• Not checked yetcites Antony et al. 2012
• Not checked yetcites Cox et al. 2012

In the paper

“The importance of the link between SOs and spindles is underscored by the finding that their coupling predicts the degree of memory strengthening over sleep (e.g., Latchoumane et al. 2017).”

What the sources say

• Not checked yetcites Latchoumane et al. 2017

In the paper

“Furthermore, manipulating SOs during sleep also increases sleep spindles (e.g., Marshall et al. 2006).”

What the sources say

• Not checked yetcites Marshall et al. 2006

In the paper

“However, SO enhancement has also occurred in the absence of observed memory improvements (Cox et al. 2014, Weigenand et al. 2016, Henin et al. 2019, Papalambros et al. 2019).”

What the sources say

• Not checked yetcites Cox et al. 2014
• Not checked yetcites Weigenand et al. 2016
• Not checked yetcites Henin et al. 2019

In the paper

“In rodents, consistent evidence has suggested a causal role for rapid eye movement (REM) sleep in memory consolidation (Smith 1995, Rasch & Born 2013, Klinzing et al. 2019).”

What the sources say

• Not checked yetcites Smith 1995
• Not checked yetcites Rasch & Born 2013
• Not checked yetcites Klinzing et al. 2019

In the paper

“The chief finding from recent TMR studies was confirmed by a meta-analysis that included results from over 90 experiments (Hu et al. 2020): When TMR was applied during SWS or N2, memory was selectively improved for the associated information compared to comparable information for which TMR was not applied.”

What the sources say

• Not checked yetcites Hu et al. 2020

In the paper

“However, Tilley also reported a TMR effect for sounds presented during N2.”

What the sources say

• Not checked yetcites Tilley 1979

In the paper

“Both low-frequency EEG power and SWS duration have repeatedly been found to be correlated with memory improvement over sleep, primarily for declarative memory (e.g., Backhaus et al. 2007, Westerberg et al. 2012).”

What the sources say

• Not checked yetcites Backhaus et al. 2007
• Not checked yetcites Westerberg et al. 2012

In the paper

“Sharp-wave/ripple complexes (SWRs), found locally in the hippocampus, are nested in the troughs of thalamo-cortical sleep spindles, which, in turn, ride on the peaks (or up-states) of cortical slow oscillations (SOs).”

In the paper

“This research approach began to gain widespread interest following a study by Rasch et al. (2007), wherein a spatial-learning improvement was produced using a rose odor during learning and again during SWS (Figure 2b).”

What the sources say

• Not checked yetcites Rasch et al. 2007

In the paper

“Accordingly, declarative memories are characterized by their reliance on novel cross-cortical connections (Paller 2002).”

What the sources say

• Not checked yetcites Paller 2002

In the paper

“Additional studies in rodents showing coordinated replay between the hippocampus and the neocortex during sleep suggest that replay is an essential aspect of the hippocampal–neocortical dialogue that can stabilize cortical representations (Foster 2017).”

What the sources say

• Not checked yetcites Foster 2017

In the paper

“This reactivation may support consolidation whether or not there is a concurrent experience of conscious retrieval.”

In the paper

“Memory processing may be particularly effective during sleep due to its unique physiological and neurochemical properties (see the sidebar titled Sleep Physiology).”

In the paper

“The hippocampus presumably helps fulfill the need to rapidly acquire declarative memories (Marr 1971, McClelland et al. 1995, Norman et al. 2005), which is not the forte of the cortex working by itself (perhaps with some exceptions; see Hebscher et al. 2019).”

What the sources say

• Not checked yetcites Marr 1971
• Not checked yetcites McClelland et al. 1995
• Not checked yetcites Norman et al. 2005

In the paper

“The jury is still out on this idea, but it seems clear at this point that many types of memory are subject to change in one way or another during sleep (Rasch & Born 2013).”

What the sources say

• Not checked yetcites Rasch & Born 2013

In the paper

“In addition, the hippocampus may continue to be involved in retrieval for some memories with regard to specific episodic details (Nadel & Moscovitch 1997, Miller et al. 2020).”

What the sources say

• Not checked yetcites Nadel & Moscovitch 1997
• Not checked yetcites Miller et al. 2020

In the paper

“A rapidly growing body of research is steadily elucidating how the consolidation of memories depends on their reactivation during sleep.”

In the paper

“Consolidation may indeed be more effective, and less subject to interference or contamination, when memories are reactivated during sleep.”

In the paper

“Declarative memories can be gradually stabilized via a slower process whereby cortical networks are altered under hippocampal guidance.”

In the paper

“The apparatus of the medial temporal lobe, centrally including the hippocampus, provides the neocortex with the capacity for storing declarative memories in an enduring way.”

In the paper

“Although consolidation may include many mechanisms operative over long periods of time (Dudai 2012), a crucial part of the consolidation process may occur over periods of sleep.”

What the sources say

• Not checked yetcites Dudai 2012

In the paper

“A putative mechanism for declarative memory consolidation involves the offline engagement of the same neural circuits involved in learning, thereby reinstating the learning-related activity in the service of memory reactivation.”

In the paper

“Many findings now support the idea that memory reactivation during both waking rest periods and sleep is relevant for the modification, integration, and stabilization of memories.”

In the paper

“Importantly, plasticity can still be operative in neural circuits, though various views on the cellular mechanisms of plasticity during sleep have been controversial.”

In the paper

“Increasing empirical support has convincingly linked spindles with memory consolidation (Antony et al. 2018, Cairney et al. 2018), though the literature on spindles historically emphasized many other functions, such as sensory processing and intelligence (Fernandez & Luthi 2020).”

What the sources say

• Not checked yetcites Antony et al. 2018
• Not checked yetcites Cairney et al. 2018

In the paper

“In this way, an interaction between hippocampal networks and cortical networks could enhance cortico-cortical connections to solidify a complete declarative memory trace.”

In the paper

“The initial cortical activity, corresponding to an incomplete memory trace, determines which memory will be reactivated.”

In the paper

“A rapid flow of information engaging a cortical-hippocampal-cortical loop can thus be described (Rothschild et al. 2017, Lewis & Bendor 2019, Rothschild 2019).”

What the sources say

• Not checked yetcites Rothschild et al. 2017
• Not checked yetcites Lewis & Bendor 2019
• Not checked yetcites Rothschild 2019

In the paper

“Nevertheless, the existing results offer considerable support for the notion that SOs function as a driving mechanism for strengthening memories during sleep.”

In the paper

“Importantly, synaptic downscaling and active consolidation are not mutually exclusive.”

In the paper

“Recent accounts emphasize the critical contributions of both reactivation and synaptic downscaling for retaining old memories and for encoding new ones (Klinzing et al. 2019).”

What the sources say

• Not checked yetcites Klinzing et al. 2019

In the paper

“Accordingly, consolidation is enabled by a synchronized temporal frame for communication among brain areas (Diekelmann & Born 2010).”

What the sources say

• Not checked yetcites Diekelmann & Born 2010

In the paper

“Neural evidence that could causally link reactivation with consolidation faces several interpretive challenges.”

In the paper

“In fact, the causal role of SWRs in memory consolidation has received more support than that of hippocampal replay (Laventure & Benchenane 2020).”

What the sources say

• Not checked yetcites Laventure & Benchenane 2020

In the paper

“REM has also been empirically associated with solving word problems using solution hints from an ostensibly unrelated task (Cai et al. 2009).”

What the sources say

• Not checked yetcites Cai et al. 2009

In the paper

“Yet, some studies failed to find sleep benefits for problem solving (Brodt et al. 2018, Schönauer et al. 2018).”

What the sources say

• Not checked yetcites Brodt et al. 2018
• Not checked yetcites Schönauer et al. 2018

In the paper

“Because this TMR procedure apparently weakened those memories, we can infer that those memories became associated with the suppression action.”

In the paper

“Such efforts have achieved limited success in the circumscribed territory of associative learning (Arzi et al. 2012) and perceptual learning (Andrillon et al. 2017).”

What the sources say

• Not checked yetcites Arzi et al. 2012
• Not checked yetcites Andrillon et al. 2017

In the paper

“Cartwright (1990) found that dreams during a single night sometimes all relate to a common theme, drawing on relevant knowledge from progressively further back in time.”

What the sources say

• Not checked yetcites Cartwright (1990)

In the paper

“Complementing these neuroimaging findings, results from a study in epileptic patients suggested that one requirement for TMR is a relatively intact medial temporal region (Fuentemilla et al. 2013).”

What the sources say

• Not checked yetcites Fuentemilla et al. 2013

In the paper

“In another study, TMR was accomplished using a sound associated with learning to suppress a memory (Simon et al. 2018). The results showed that new associations were formed during sleep when this suppression-related sound was presented along with sounds related to other memories.”

What the sources say

• Not checked yetcites Simon et al. 2018

In the paper

“A follow-up study showed that EEG activity during SWS in the form of power in the beta band (17–25 Hz) and perhaps part of the spindle band (10–11 Hz) predicted which participants would discover the shortcut (Verleger et al. 2013).”

What the sources say

• Not checked yetcites Verleger et al. 2013

In the paper

“These results from TMR studies also converge with findings from studies of spontaneous reactivation that have also implicated spindles as a crucial component in decoding reactivated content (Bergmann et al. 2012, Schönauer et al. 2017).”

What the sources say

• Not checked yetcites Bergmann et al. 2012
• Not checked yetcites Schönauer et al. 2017

In the paper

“New learning during sleep may be limited to simple types of memory.”

In the paper

“In rodents, TMR was used to directly link memory reactivation with hippocampal replay: When tones associated with spatial learning on a two-arm maze were played during NREM sleep, corresponding hippocampal place cells were preferentially reactivated over the next few seconds (Bendor & Wilson 2012).”

What the sources say

• Not checked yetcites Bendor & Wilson 2012

In the paper

“Accordingly, an optimal time for cue presentation is at the end of this refractory period.”

In the paper

“These results were thus used to support the cortical-hippocampal-cortical loop theory of reactivation-dependent memory consolidation outlined above.”

In the paper

“In a subsequent study in rodents, Rothschild et al. (2017) found that a sound cue associated with pre-sleep learning biased auditory cortex activity, which predicted hippocampal SWR activity.”

What the sources say

• Not checked yetcites Rothschild et al. (2017)

In the paper

“For example, two distinct memories may become associated, such as when a connection emerges between a recent event and a remote event.”

In the paper

“Reinstatement of memory-specific neural signatures following cues has been observed using both EEG and fMRI (Belal et al. 2018, Cairney et al. 2018, Schreiner et al. 2018, Shanahan et al. 2018, Wang et al. 2018).”

What the sources say

• Not checked yetcites Belal et al. 2018
• Not checked yetcites Cairney et al. 2018
• Not checked yetcites Schreiner et al. 2018

In the paper

“Such connections can also be the basis for creativity and problem solving.”

In the paper

“Overnight, half of the themes were presented during SWS, which functioned to selectively increase the likelihood of producing solutions for those puzzles compared to the remaining puzzles.”

What the sources say

• Not checked yetcites Sanders et al. (2019)

In the paper

“Although factors such as testing effects, forgetting, interference, and consolidation may all affect retrieval after a delay, and potentially confound memory comparisons between a retention period with sleep and one without sleep, differential memory changes due to a TMR manipulation can be firmly attributed to differential consolidation for cued relative to uncued memories.”

In the paper

“The available evidence is broadly consistent with the supposition that memory processing during sleep can be useful for various cognitive challenges that arguably share some properties with creativity.”

In the paper

“Yet, sound experimental designs in typical TMR studies still allow for valid comparisons between two conditions, one with and one without TMR cues presented during sleep, using either between-subjects or within-subjects comparisons.”

In the paper

“The relative benefit in recall accuracy for cued compared to uncued conditions, as now observed in many TMR studies (Hu et al. 2020), demonstrates that stimuli presented during sleep can function to reactivate specific memories.”

What the sources say

• Not checked yetcites Hu et al. 2020

In the paper

“Two of these studies showed that this reactivation coincided with spindle activity (Cairney et al. 2018, Wang et al. 2018), converging with the aforementioned evidence implicating spindles.”

What the sources say

• Not checked yetcites Cairney et al. 2018
• Not checked yetcites Wang et al. 2018

In the paper

“For example, reprocessing of recent episodic memories during sleep can support gist abstraction and generalization, which are useful modes of memory transformation (Lewis & Durrant 2011, Lutz et al. 2017, Schapiro et al. 2017, Tamminen et al. 2017).”

What the sources say

• Not checked yetcites Lewis & Durrant 2011
• Not checked yetcites Lutz et al. 2017
• Not checked yetcites Schapiro et al. 2017

In the paper

“Other evidence supports the idea that REM sleep may be an optimal time for broad semantic associations that are perhaps indicative of creativity (Stickgold et al. 1999).”

What the sources say

• Not checked yetcites Stickgold et al. 1999

In the paper

“Within-subject comparisons then allowed nonspecific effects of sleep, such as alertness and interference, to be ruled out.”

In the paper

“Their results showed that memory reactivation was most effective when a spindle occurred shortly after a TMR cue.”

What the sources say

• Not checked yetcites Antony et al. 2018

In the paper

“Higher creativity was found when task-related odors were presented overnight compared to different-odor and no-odor control conditions in other participants.”

What the sources say

• Not checked yetcites Ritter et al. 2012

In the paper

“TMR can improve many other types of learning in addition to spatial learning, including many examples of both declarative and nondeclarative memory [Hu et al. (2020) provide a comprehensive list as of mid-2019].”

What the sources say

• Not checked yetcites Hu et al. (2020)

In the paper

“Notably, emotional benefits from sleep may be secondary to memory reorganization (Vanderheyden et al. 2015).”

What the sources say

• Not checked yetcites Vanderheyden et al. 2015

In the paper

“SWS has garnered far less attention in research on depression and related disorders, but given the wealth of evidence supporting the role of SWS in memory consolidation, it may be more relevant in this context than commonly assumed.”

In the paper

“Bringing together the critical role of sleep in memory consolidation with the fact that memory is used for many cognitive functions leads to the following further inference: Sleep disturbances may have far-reaching cognitive consequences.”

In the paper

“Memory symptoms noted in depression, particularly overgeneral autobiographical retrieval (Williams et al. 2007), may also fit with the dependence of memory function on sleep and the alteration of sleep in depression.”

What the sources say

• Not checked yetcites Williams et al. 2007

In the paper

“First, patients suffering from MDD exhibit reduced slow-wave activity relative to healthy controls (Borbély et al. 1984).”

What the sources say

• Not checked yetcites Borbély et al. 1984

In the paper

“Emotional memories likely benefit from arousal-related tagging during encoding (Payne & Kensinger 2018).”

What the sources say

• Not checked yetcites Payne & Kensinger 2018

In the paper

“Supporting sleep’s suggested role in overemphasizing the consolidation of negative memories, one TMR study found that cueing negative memories resulted in more negative ratings one week later in socially anxious adolescents but not in healthy ones (Groch et al. 2017).”

What the sources say

• Not checked yetcites Groch et al. 2017

In the paper

“In an fMRI study, reduced top-down cognitive control was evident in sleep-deprived compared to control participants (Yoo et al. 2007).”

What the sources say

• Not checked yetcites Yoo et al. 2007

In the paper

“Consonant with this idea, depressed patients tend to recall negative memories better than healthy individuals do (Fattahi Asl et al. 2015).”

What the sources say

• Not checked yetcites Fattahi Asl et al. 2015

In the paper

“In one study, women exposed to a traumatic movie followed by a period of sleep experienced fewer traumatic memories when compared with women exposed to the traumatic movie followed by a neutral movie (Kleim et al. 2016).”

What the sources say

• Not checked yetcites Kleim et al. 2016

In the paper

“A bidirectional relationship is likely, as sleep and affective symptoms may reinforce each other throughout the progression of MDD (Bao et al. 2017).”

What the sources say

• Not checked yetcites Bao et al. 2017

In the paper

“Correspondingly, the three major classes of antidepressant drugs all profoundly suppress REM sleep (Vertes & Eastman 2000).”

What the sources say

• Not checked yetcites Vertes & Eastman 2000

In the paper

“Various findings support the claim that emotional memories are preferentially consolidated during sleep.”

In the paper

“Relatedly, bright-light therapy can be helpful in depression, in conjunction with its effects on circadian rhythms and sleep (Pail et al. 2011).”

What the sources say

• Not checked yetcites Pail et al. 2011

In the paper

“Although amygdala activity is increased during REM sleep (Maquet et al. 1996), TMR cues improved emotional memories not when presented during REM but rather when presented during NREM (Lehmann et al. 2016).”

What the sources say

• Not checked yetcites Maquet et al. 1996

In the paper

“The cumulative research using TMR shows that sleep-based consolidation is modifiable.”

In the paper

“An excess of arousals during REM sleep may be one sign of maladaptive sleep in relation to emotional distress.”

In the paper

“That is, sleep may be helpful for arousal regulation not on the next day but after some number of days.”

In the paper

“The latter direction of causality has received considerable support, including evidence that sleep abnormalities often precede depressive episodes (Ohayon & Roth 2003).”

What the sources say

• Not checked yetcites Ohayon & Roth 2003

In the paper

“To examine the association between this sign of low-quality sleep and emotional coping, Wassing and colleagues (2019) subjected healthy individuals to an episode of self-focused distress, and they found that sleep with abundant spindles followed by uninterrupted REM sleep predicted a healthier orientation the next day, as reflected by an adaptation in amygdala fMRI activity (Figure 4).”

What the sources say

• Not checked yetcites Wassing et al. (2019)

In the paper

“TMR cues improved emotional memories not when presented during REM but rather when presented during NREM (Lehmann et al. 2016).”

What the sources say

• Not checked yetcites Lehmann et al. 2016

In the paper

“Indeed, a pre-sleep hypnosis procedure has been shown in several studies to increase sleep physiology measures of SWS in highly hypnotizable young subjects (e.g., Cordi et al. 2020).”

What the sources say

• Not checked yetcites Cordi et al. 2020

In the paper

“In one study, TMR during sleep following such training was found to enhance bias changes, as indexed by performance measures from the Implicit Association Test (Hu et al. 2015).”

What the sources say

• Not checked yetcites Hu et al. 2015

In the paper

“Indeed, recurring nightmares or recurring stressful dreams could be a symptom of more pervasive suboptimal sleep.”

In the paper

“Whereas Wassing and colleagues (2019) used TMR to reinstate the context of a particularly stressful and negative affect-laden experience”

What the sources say

• Not checked yetcites Wassing and colleagues (2019)

In the paper

“Also, one attempt to closely replicate these TMR results failed to do so (Humiston & Wamsley 2019).”

What the sources say

• Not checked yetcites Humiston & Wamsley 2019

In the paper

“Dream control provides a further demonstration that we are not helplessly at the mercy of whatever happens during sleep.”