Memory consolidation Flashcards
2 types of memory?
stages of memory processing?
declarative (what)
non-declarative (how)
Your brain oscillate between a variety of different sleep stages
1) form representation of event (vulnerable to being overridden)
2) memory consolidation
( required to make memory last long term)
–> can then recall it, integrate it with existing info and modify it
Models of sleep and memory consolidation
3 models + brief description
1) dual process model
- focuses on specific components of sleep eg. REM and NREM
- explains how different sleep stages help with different types of memory consolidation
eg.
SWS helps consolidate DECLARATIVE
REM helps consolidate NON-DECLARATIVE
(Ficcaa, 2014)
2) Two-step model
- interested in the REM-NREM cycle (2 components together and how we go back and forth between them)
- explains the importance of successive cycle of REM and SWS sleep stages
suggests:
in SWS:
- non-adaptive memories weakened
- adaptive memories strengthened
in REM:
- adaptive memories are integrated with existing memory networks
3) active systems consolidation hypothesis
= integration of the 2 models: focus on individual stages of sleep and the cycle of REM-NREM
- SWS stage has upper hand in the process of memory consolidation with repetitive reactivation of newly encoded info
–> move STM to LTM by repetitive reactivation of sharp wave ripple in the hippocampus and thalamo-cortico spindle
- REM acts as a support system for SWS. Stabilizes the synaptic consolidation process
Dual process model
(Ackermann & Rasch, 2014)
- paradigm used to test this?
- limitations?
- night paradigm used to test this
- participants tested after SWS sleep or REM sleep, but not both (1st half of night = SWS, 2nd = REM)
- SWS = greater recall of declarative
-REM = greater recall of non-declarative
(stage 2 seems to play a role in motor tasks specifically)
BUT,
too simplistic? - what about info that is declarative and non-declarative
- what about the other stages? eg. stage 2
Two-step model
- 2 steps?
- strengths
- weaknesses
step 1: non-adaptive memories are weakened during SWS
step 2: adaptive memories are integrated in REM sleep
– doesn’t specifically say specific memory is consolidated in certain stages
essentially:
- SWS filters out nonsense, remainder is consolidated and integrated with other memories in REM
- During SWS memories to be retained are distinguished from irrelevant or competing traces that undergo downgrading or elimination
- processed memories are stored again during REM sleep which integrates them with pre-existing memories
STRENGTHS:
- supported by human and animal research
- sleep stages aren’t viewed in isolation
- cyclic structure of sleep is important
LIMITATIONS:
- difficult to test directly
- what are the exact functions of each sleep stage
Active system consolidation model
(Born et al; 2006, 2011, 2012)
How?
necessary components? (2)
-integrates aspects of both models
= a key model in memory consolidation
- provides a background for the process of memory reactivation and reorganisation
- memories that are first learned are encoded into the hippocampus and the neocortex (outer area of brain)
–> these neocortical memory nodules are thought to exist in a highly distributed form
- when a memory is fairly new or not v consolidated its thought that the hippocampus via hippocampal neocortical connections binds together these highly distributed memory nodules in order to bring a coherent representation to consciousness
HOW?
- during SWS–> slow oscillations are thought to drive a reactivation memory in both the hippocampus and neocortex, this leads to a weakening of hippocampal neocortical connections and a concurrent strengthening in cross cortical connections
= the memory is no longer dependent on the hippocampus and entirely dependent on neocortex
= can be retrieved independently of the hippocampus and is now thought to be integrated into LTM
Necessary components for reorganisation of memory?:
1) slow oscillations
2) reactivation of memory nodules
- REM is important for integrating these memories into current memories and strengthening synaptic connections
Forming memories
3 phases
LEARNING PHASE is the initial component
= when we learn new info we encode a representation in the brain
CONSOLIDATION - to move the info into LTM it undergoes consolidation
= strengthening/ stabilising of memories. Sleep benefits consolidation in a way that can’t be achieved by wakefulness
RETRIEVAL - the latter stage of memory
= when we are able to bring a coherent representation to consciousness
(consolidate when we’re awake a little bit, but mainly when we’re asleep)
Targeted memory consolidation
- study Rasch et al, 2007
- Rudoy et al, 2009 - specific memories
key part of active systems consolidation model is the reactivation of memories in your sleep
- you can manipulate what’s going on when people are asleep and what is reactivated
- memory reactivations in sleep can be triggered by sounds and odours
eg. exposed to sound during encoding period, you can cue the reactivation with this sound during SWS
- sounds may trigger hippocampal replay - artificial enhancement of normal process
(benefit declarative but not procedural learning)
–> ONLY when presented in SWS, not REM
p’s learned card locations, then underwent test phase (recall locations)
- in learning phase they were exposed to an odour (rose) = contextual cue to be used later
- when in SWS they were exposed to rose odour OR vehicle control (puff of air)
found: if memory reactivation were cued dueing sleep they performed better at task (improved performance was specific to odour presentation during LEARNING phase and cue during SWS only)
+ physiological evidence - repeated using FMRI and found: when they delivered the odour specifically the hippocampus lit up during SWS
( = behavioural and physiological evidence for the importance of memory reactivation in memory consolidation)
specific memories:
- study looked at whether you can reactivate specific memory representations using sounds (Rudoy et al, 2009)
- p’s shown 50 objects (each accompanied by a corresponding tone)
during SWS period, 25 sounds were replayed (only 1/2)
looked at decline in memory and found: extent of memory decline was significantly lower for items that has been cued by sound !
Sleep memory and age
- typical features of elderly people’s sleep
- sleep architecture changes as we age
- see a decrease in SWS as we age (30+ = decline)
- hypnograms of young and old
-elderly tend to have:
fragmeneted sleep
delayed sleep onset
early-morning awakening
decreased SWS (3+4)
= affects memory consolidation/ increased awakening
Reasons why SWS sleep declines as we age and why one might experience sleep disturbances
How does this affect memory?
- young vs old SW
changes in the bodys internal clock (changes in cell bodies in brain)
degeneration of the medial frontal cortex (affects maintenance of sleep)
comorbidities
side effects of medications
need to urinate more frequently
pain caused by diseases eg. arthritis
stimulants such as nicotine/ caffeine
How does it?
SWS needed for memory consolidation. So, if sleep declines so does our ability to consolidate memories
- In young healthy adults SWS brain wave are perfectly synchronised –> helps with the consolidation of memories
- as we get older = no longer synchronised electrical activity. So, the firing of neurons is misaligned = affects the consolidation process
YOUNG = slow wave oscillations are in line with the peak of the sleep spindle
OLDER = slower wave oscillations are not in line with the peak of the sleep spindle
(Helfrich et al, 2018)
–> currently trying to develop new electrical brain stimulation tech to try and re-synchronise the brain oscillations in SWS in older adults
Sleep and false memories
for EWT this is an important association look at: - how memories are consolidated - how memories are stored - how memory representations change over time (whether these are useful or adaptive)
Research has found both sleep and sleep loss can increase the formation of false memories
- mixed results have been found regarding sleep and false memories (some suggest increase in formation of false memories, some show a decrease)
- sleep deprivation suggested to increase formation of false memories
