Sleep - sleep and memory consolidation

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The different sleep stages
Wake; NREM (stage 1, stage 2. Deep sleep - stage 3, stage 4); REM
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The different memory types
Declarative (episodic, semantic); non-declarative (procedural skills, conditioning, non-asociative, priming)
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The different memory stages
Encoding(brain forms a representation)--> consolidation(memory is fragile&vulnerable to being over ridden-consolidate to persist long term) --> association/integration (with existing information) --> recall/recognition --> reconsolidation --> erasure
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We know that your brain oscillates between a ....
variety of different stages of sleep. Going from being awake to being a sleep and of course going through the different stages of sleep.
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Just as the brain has different states, there a different types of ....
memories. The way memory is classified is whether it’s declarative or non-declarative.
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So when we explore the role of sleep and memory it’s much more ....
complex than we initially thought. Which stage of sleep are we interested in? Which type of memory are we referring to? Which stage of memory is it related to?
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Dual process model (Ackermann & Rasch, 2014) - focuses...
specific components of sleep i.e. NREM and REM.
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Dual process Model (Ackermann & Rasch, 2014) - explains how ...
how different sleep stages help with different types of memories consolidation. This hypothesis shows that SWS sleep helps consolidation of declarative memories while REM sleep helps with non-declarative memories.
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Two-step model- interested in ....
in the NREM-REM cycle.
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The Two-Step Model explained ....
the importance of successive cycle of REM & SWS stages in sleep by saying that during SWS non adaptive memories were weakened&adaptive response were strengthen but during REM sleep,adaptive memories are integrated with the existing memory networks
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The active systems consolidation hypothesis (Born et al., 2012) an integration of ....
the two model and is not only interested in the individual stages of sleep but also cycling of NREM to REM.
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The active systems consolidation model (Born et al., 2012)- The SWS stage will take the upper hand in this process that ....
causes memory consolidation during sleep with repetitive reactivation of newly encoded information.
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The active systems consolidation model (Born et al., 2012)- during the SWS stage....
the brain tries to help adaptation of STM to LTM by repetitive reactivations of the sharp wave ripple in the hippocampus together with thalamo-cortical spindle.
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The active systems consolidation model (Born et al., 2012)- REM
REM sleep will act as a support system for SWS sleep as every memory activation and consolidation happening, it will stabilize the synaptic consolidation process.
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Ackermann & Rasch, 2014 - Dual Process Model - night paradigm
The night-half paradigm is used to test this- This is where participants are tested after a period of SWS sleep or a period of REM sleep but not both.
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Ackermann & Rasch, 2014 - Dual Process Model - due to our circadian rhythm...
the ratio of SWS is higher in the first part of the night and the ratio of REM is higher in the second part of the night.
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Ackermann & Rasch, 2014 - Dual Process Model - proposes that...
declarative memories are associated with the SWS component whilst non-declarative memories are associated with REM sleep.
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Ackermann & Rasch, 2014 - Dual Process Model - a further extension of this model proposes that...
simpler motor tasks are associated with stage 2 sleep.
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Is the Dual Process Model too simplistic? - a major weakness of the night-half paradigm is that it ignores possible contributions of stage 2 sleep to memory....
Although the amounts of stage 2 sleep were comparable in the early&late sleep conditions of the studies reported above, sleep in this sleep stage may have substantially differed between the two phases,e.g.spindle density (de Gennaro & Ferrara, 2003)
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Two-step model - earlier hypotheses for this model propose that....
non-adaptive memories (memories that are not important) are weakened during SWS and adaptive memories are integrated in REM sleep. However, over the last two decades the research suggests a role for SWS in memory consolidation.
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Two-step model - SWS
During SWS memories to be retained are distinguished from irrelevant or competing traces that undergo downgrading or elimination
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Two-step model -REM
Processed memories are stored again during REM sleep which integrates them with pre-existing memories.
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Strengths of the two-step model
Supported by animal and human evidence Sleep stages are not viewed in isolation Cyclic structure of sleep is important
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Limitations of the two-step model
Difficult to test directly What are the exact functions of each sleep stage?
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The active system consolidation model (Born et al., 2012) integrates some aspects of the ...
dual process model and the two step model. Specific stages of sleep are important for memory consolidation The cycling between non-REM and REM is also important
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Forming memories - when we form memories...
the initial component is the learning phase. When we learn new information we encode a representation in our brain. After a period of time we have the latter stage of memory which is retrieval,where are able to bring a representation to consciousness
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Forming memories - when we encode new information into our brain...
it’s not automatically integrated into our long term memories., It needs to undergo a process known as consolidation. This consolidation process is fundamental to our ability to retain information in the future
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Forming memories - consolidation refers to a....
strengthening or stabilisation of memories.
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Forming memories - Sleep benefits....
consolidation in a way that can’t be achieved by wakefulness.
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Born et al., 2012
Active Systems Consolidation - A key model in memory consolidation. This models provide a background to what we think is going on in terms of memory reactivation and reorganisation.
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Born et al., 2012 - the memories are first encoded or learned they're....
encoded both into the hippocampus (green nodes) and also into the neocortex (orange nodes).
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Born et al., 2012 - these neocortical memory nodules are thought to exist in a....
highly distributed form
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Born et al., 2012 - When a memory is fairly new or it’s under gone very little consolidation, it’s thought that the....
the hippocampus via hippocampal neocortical connections binds together these highly distributed memory nodules in order to bring a coherent representation to consciousness.
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Born et al., 2012 - Slow oscillations are thought to drive a ....
reactivation of memory in both the hippocampus and neocortex, this leads to a weakening of hippocampal neocortical connections and a concurrent strengthening in cross cortical connections.
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Born et al., 2012 - when this process is completed....
the memory is no longer dependent on the hippocampus and entirely dependent on the neocortex. So now you can retrieve it independently of the hippocampus and it’s now thought to be integrated within your long term memory.
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Born et al., 2012 - what is important is that....
these slow oscillations and the reactivation of these memory nodules are necessary for this reorganisation of memory.
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Born et al., 2012 - REM is important for....
integrating these memories and strengthen the synaptic connections.
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Targeted Memory Reactivation (TMR) - A key part of the active systems consolidation model is the ....
reactivations of memories in your sleep.
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Targeted Memory Reactivation (TMR) - You can actually manipulate what’s going on when ....
people are asleep and what’s reactivated.
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Targeted Memory Reactivation (TMR) - Memory reactivations in sleep can be triggered by ....
sounds&odours.E.g.during the encoding period if you are exposed to a specific sound/smell you can cue the reactivation of this information when you’re asleep.During sleep if you are exposed to the specific sound/smell,the memories can be reactivated
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Targeted Memory Reactivation (TMR) - sounds may trigger....
hippocampal replay – artificial enhancement of normal process.
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Targeted Memory Reactivation (TMR) - Benefit declarative but not ....
procedural learning.
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Targeted Memory Reactivation (TMR) - when presented in what stage of sleep?
When presented in SWS but not REM sleep.
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Rasch et al. (2007) - background
One of the first studies that looked at targeted reactivations was carried out over 10 years ago.
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Rasch et al. (2007) - They got participants to carry out a task where they ....
learning card locations (e.g. a picture of a car).
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Rasch et al. (2007) - Once they learned the locations of the cards then they....
underwent a test phase, where they had to recall these locations
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Rasch et al. (2007) - Whilst they underwent this training to ....
learn the locations of these cards they were exposed to an odour (rose).
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Rasch et al. (2007) - When they went to sleep, ....
during SWS they were presented with the odour again or vehicle (control group).
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Rasch et al. (2007) - The idea was that by ....
re-introducing this odour it would act as a contextual cue for memory representations associated with this odour, which would then be reactivated and consolidated.
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Rasch et al. (2007) - They examined this by ....
testing participants again after sleep. When you compare the odour condition to the vehicle it shows a significant impact on the memory. If memory reactivations were cued during sleep they performed better.
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Rasch et al. (2007) - They carried out lots of....
control experiments, showing that improved performance was specific to odour presentation during the learning phase and during SWS only.
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Rasch et al. (2007) - What’s key is that the ....
odour needs to be presented during the learning phase and again during SWS for this to have any benefits.
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Rasch et al. (2007) - They repeated the study ....
using fMRI. What they found that when they delivered the odour specifically the hippocampus lit up during SWS. So they have both behavioural and physiological evidence for the important of memory reactivations in memory consolidation.
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Rudoy et al. (2009) - background
A later study by Rudoy et al went on to investigate whether you could target specific memories and reactivate specific memory representations using sounds.
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Rudoy et al. (2009) - In this study participants were shown....
50 objects, each of these were accompanied by the corresponding sound
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Rudoy et al. (2009) - During the learning phase they ....
learnt the location of these objects.
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Rudoy et al. (2009) - Then participants took a ....
which included a period of SWS, during this SWS period 25 of the sounds were replayed.
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Rudoy et al. (2009) - After the nap they ....
underwent a test phase where they assessed the difference between the cued and uncued sounds by looking at the decline in memory.
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Rudoy et al. (2009) - Findings
What they found was that the extent of the memory decline was significantly lower for items that had been cued by the sounds during sleep.
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Carskadon and Rechtschaffen (2005)
Sleep, Memory and Age. Sleep architecture changes as we age. Found a decrease in SWS as we age. It’s well known that memory declines with age. Is there a connection between changes is sleep architecture and decline in memory?
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Neubauer (1999)
Hypnograms demonstrating typical sleep characteristics in young adults and elderly persons. Compared with young adults, the elderly tend to have delayed sleep onset, fragmented sleep,early-morning awakening&decreased time in sleep stages 3 and 4(SWS)
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reasons why SWS sleep declines as we age and why one might experience sleep disturbances.
Changes in the body’s internal clock Degeneration of the medial Frontal Cortex Comorbidities Side effects of medications Need to urinate more frequently Pain caused by diseases such as arthritis. Stimulants such as nicotine/caffeine
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Helfrich et al. (2018) - background
How does older adults problems with sleep/less time in SWS affect memory? We know that SWS is important for memory consolidation. So if SWS sleep declines so does our ability to consolidate memories
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Helfrich et al. (2018) - In young healthy adults the Brain waves associated with SWS are ....
perfectly synchronised. This synchronised helps with the consolidation of memories.
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Helfrich et al. (2018) - But as we get older the electrical activity in SWS is ....
no longer synchronised. So the firing of the neurons is misaligned which affects the consolidation process.
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Helfrich et al. (2018) - the Slow wave oscillations in younger adults is in line with the ....
peak of the sleep spindle.
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Helfrich et al. (2018) - However, in older adults the sleep spindle is ....
not in line with the Slow oscillations.
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Helfrich et al. (2018) - in older adults, the size of the slow wave will be....
smaller. This is because there are fewer neurons firing at the same time.
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Sleep and False Memories - Understanding whether sleep affects the formation of false memories is important because it ...
is directly related to questions about how memories are consolidated and stored, how memory representations change over time, and whether these changes can be useful and adaptive.
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Sleep and False Memories - This is particularly important for the ...
criminal justice system- eye witness testimonies.
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Sleep and False Memories - Research in this field has found that both sleep and sleep loss can...
increase the formation of false memories.
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Sleep and False Memories - Research on the role of sleep in forming false memories has found mixed results. Some studies showing that ...
sleep can increase the formation of false memories (Payne et al., 2009)and other showing that sleep reduces the formation of false memories (Fenn et al., 2009)
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***Lo et al., 2016***
Sleep deprivation increases the formation of false memories
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Summary - There are different models of ....
sleep and memory consolidation.
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Summary - The active system consolidations model proposes that ....
SWS is critical for reactivation and reorganisation of memories for long term storage.
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Summary - Evidence for targeted reactivation of ....
specific memory representations through sensory cues. Suggesting that we can manipulate the memories which are reactivated and consolidated.
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Summary - There are wider implications for ....
sleep and memory research.
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***Tilley et al., 1992***
It is now acknowledged that sleep is more effective than wakefulness for memory consolidation of waking events
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***Smith, 2001 - background***
As well as studies using the night-half paradigm,a differential role of sleep stages in memory consolidation is supported by numerous studies investigating the influence of selective sleep stage deprivation on memory consolidation.Reviewed by Smith
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***Smith, 2001 - procedural***
results strongly suggest that selective REM sleep deprivation impairs the consolidation of cognitive procedural tasks, such as the tower of Hanoi task or word fragment completion
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***Smith, 2001 - simple declarative***
the consolidation of simple declarative memories (word lists, paired associates, etc.) remains intact
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***Smith, 2001 - complex declarative***
However, memory for the more complex declarative memories (anomalous prose, meaningless sentences, stories) was impaired by REM sleep deprivation
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***Smith, 2001 - However, this may have been because the...***
students in this study, based on years of similar school experience, had more developed strategies to memorise word memories. They may have had less well-developed strategies to memorise the anomalous prose, meaningless sentences and stories
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***Alger et al., 2012 - background***
In relation to active system consolidation hypothesis - Many recent human studies have found evidence for the importance of SWS for hippocampus-dependent declarative memory
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***Alger et al., 2012 - found***
found that only a 60-minute nap (containing SWS), but not a 10-minute nap, protected memory from future interference on a paired association task. The same pattern was also found when memory stability was tested one week later.
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***Maquet et al., 2000***
Positron emission tomography (PE) brain imaging studies have demonstrated that on the night following training on a visuomotor procedural learning task, regions active during task performance are specifically reactivated during REM sleep in humans.
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***Wagner et al., 2006***
Sleep also supports the consolidation of emotional information. For example, effects of a 3-hour period of sleep on emotional memory consolidation were even found 4 years later
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***Fischer et al., 2002 - background***
Sleep is something that individuals usually do at night-time. However, it should not be ruled out whether the effect of sleep on memory consolidation could change depending on when the sleep occurred during the circadian rhythm 24-hour cycle
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***Fischer et al., 2002 - findings***
found that on a finger sequence tapping task, pp's improved to the same extent after 8 hours of sleep during the night and 8 hours of sleep during the day&in both instances pp's performed significantly better than corresponding periods of wakefulness
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***Fischer et al., 2002 - therefore, this suggests that...***
sleep benefits memory consolidation, regardless of when the sleep occurs.
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***Born & Rasch (2006); Gais & Born (2004)***
Considerable evidence has been found,using the night-half paradigm,for the dual process hypothesis,including evidence that hippocampus-dependent declarative memories benefit from SWS,whereas non-declarative memory additionally benefits from REM sleep
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***Independent research - Rasch et al., 2007 - Also, odour cues activate the hippocampus during SWS to a greater extent than during wakefulness. Thus, as well as showing that....***
memory-associated odour cues activate the hippocampus during SWS, this observation also suggests a sensitivity of the hippocampus during this stage of sleep to stimuli that are capable of reactivation.
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Card 2

Front

The different memory types

Back

Declarative (episodic, semantic); non-declarative (procedural skills, conditioning, non-asociative, priming)

Card 3

Front

The different memory stages

Back

Preview of the front of card 3

Card 4

Front

We know that your brain oscillates between a ....

Back

Preview of the front of card 4

Card 5

Front

Just as the brain has different states, there a different types of ....

Back

Preview of the front of card 5
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