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Summary Case 6 sleep and memory
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Case 6 from the course sleep and sleeping disorders from the bachelor psychology and advanced minor in psychology. I got a 9.5 for the exam myself.
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Case 6 sleep and memoryRelationship between sleep and memory- type of memories
How does sleep deprivation affect memory
What brain parts are involved
Odor cues
Diekelman: Memory function of sleep
- Sleep has been identified as a state that optimizes the consolidation of newly acquired
information in memory, depending on the specific conditions of learning and the
timing of sleep. Consolidation during sleep promotes both quantitative and qualitative
changes of memory representations. Through specific patterns of neuromodulatory
activity and electric field potential oscillations, slow-wave sleep (SWS) and rapid eye
movement (REM) sleep support system consolidation and synaptic consolidation,
respectively. During SWS, slow oscillations, spindles and ripples — at minimum
cholinergic activity — coordinate the re-activation and redistribution of hippocampus-
dependent memories to neocortical sites, whereas during REM sleep, local increases in
plasticity-related immediate-early gene activity — at high cholinergic and theta
activity — might favour the subsequent synaptic consolidation of memories in the
cortex
- Sleep promotes primarily the consolidation of memory, whereas memory encoding
and retrieval take place most effectively during waking. Consolidation refers to a
process that transforms new and initially labile memories encoded in the awake state
into more stable representations that become integrated into the network of pre-
existing long-term memories
- Sleep duration and timing: longer sleep durations yield greater improvements,
particularly for procedural memories. Some data suggest that a short delay between
learning and sleep optimizes the benefits of sleep on memory consolidation. For
optimal benefit on procedural memory consolidation, sleep does not need to occur
immediately but should happen on the same day as initial training
- Explicit vs implicit encoding: explicit encoding of a memory favours access to sleep-
dependent consolidation. The benefit of sleep is greater for memories formed from
explicitly encoded information that was more difficult to encode or that was only
weakly encoded and it is greater for memories that were behaviourally relevant. a
motivational tagging of memories, which probably relies on the function of the
prefrontal cortex, might signal behavioural effort and relevance and mediate the
preferential consolidation of these memories.
- Sleep changes memory representations quantitatively and qualitatively: Strengthening
of a memory behaviourally expresses itself as resistance to interference from another
similar task (‘stabilization’) and as an improvement of performance (‘enhancement’)
that occurs at re-testing, in the absence of additional practice during the retention
interval. The stabilizing effects of sleep have been observed in declarative and
procedural memory tasks. Similarly, enhancements in performance after sleep have
been shown for declarative information and in procedural tasks. There is strong
evidence for an active consolidating influence of sleep from behavioural studies,
which indicate that sleep can lead to qualitative changes in memory.
- Interacting or competing memory systems? sleep can ‘re-organize’ newly encoded
memory representations, enabling the generation of new associations and the
extraction of invariant features from complex stimuli, and thereby eventually easing
novel inferences and insights. Re-organization of memory representations during sleep
also promotes the transformation of implicit into explicit knowledge. procedural and
declarative memory systems interact during sleep-dependent consolidation. memory
1
, systems compete and reciprocally interfere during waking, but disengage during sleep,
allowing for the independent consolidation of memories in different systems.
- Sleep stages and consolidation: pharmacological suppression of REM sleep by
administration of antidepressant drugs did not impair consolidation of procedural
memory, which is in agreement with clinical observations that antidepressant
treatment does not affect memory function. SWS-rich, early sleep consistently benefits
the consolidation of declarative memories, whereas REM-rich sleep benefits
nondeclarative types of memory. SWS facilitates declarative, hippocampus-dependent
memory and REM sleep supports non-declarative, hippocampus-independent memory.
memory consolidation seems to be impaired by disruptions of the natural SWS–REM
sleep cycle that left the time spent in these sleep stages unchanged. not a particular
sleep stage per se that mediates memory consolidation, but rather the
neurophysiological mechanisms associated with those sleep stages, and that some of
these mechanisms are shared by different sleep stages.
- Reactivation memory traces during sleep: neuronal re-activation of ensemble activity
mostly occurs during SWS and during the first hours after learning, and typically only
in a minority of recorded neuron. re-activations during SWS almost always occur in
the order in which they were experienced. re-activations during SWS seem to be
noisier, less accurate and often happen at a faster firing rate. during SWS hippocampal
networks are particularly sensitive to inputs that can re-activate memories. It is
assumed that the reactivations during system consolidation stimulate the redistribution
of hippocampal memories to neocortical storage sites, although this has not been
directly demonstrated yet
- Synaptic consolidation: consolidation involves the strengthening of memory
representations at the synaptic level. long-term potentiation (LTP) is considered a key
mechanism of synaptic consolidation, but it is unclear whether memory re-activation
during sleep promotes the redistribution of memories by inducing new LTP or whether
re-activation merely enhances the maintenance of LTP that was induced during
encoding. LTP can be induced in the hippocampus during REM sleep but less reliably
so during SWS. sleep strengthened LTP-like plasticity that had been induced in the
neocortex by transcranial magnetic stimulation (TMS) prior to sleeping. local, off-line
re-activation of specific glutamatergic circuits supports both LTP induction and
maintenance, and the molecular processes underlying synaptic consolidation.
Moreover, these processes probably occur preferentially during REM sleep, although
they are likely to be triggered by the re-activations that occur during prior SWS.
- Field potentiates associated with SWS: Neocortical slow oscillations, thalamo-cortical
spindles and hippocampal ripples have been associated with memory consolidation
during SWS. Neocortical slow oscillations are thought to provide a supra-ordinate
temporal frame for the dialogue between the neocortex and subcortical structures that
is necessary for redistributing memories for long-term storage. slow oscillations have
a causal role in the consolidation of hippocampus-dependent memories. Thalamo-
cortical spindles seem to prime cortical networks for the long-term storage of memory
representations. Repeated spindle-associated spike discharges can trigger LTP and
synchronous spindle activity occurs preferentially at synapses that were potentiated
during encoding. Hippocampal sharp wave-ripples accompany the sleep-associated re-
activation of hippocampal neuron ensembles that were active during the preceding
awake experience. The occurrence of sharp waveripples is facilitated in previously
potentiated synaptic circuits and sharp wave-ripples might promote synaptic
potentiation. the consolidation of picture memories that were acquired before a nap
correlated with the number of ripples recorded from the peri- and entorhinal cortex,
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