Lecture 7 Flashcards
Why is Sleep Important?
Diekelman and Born (2010)
Memory consolidation brain plasticity and learning are thought to occur at specific stages of the sleep cycle
Sleep deprivation reduces performance and increases variability in may cognitive tasks
What is the theory about plasticity as a function of Sleep and complications with associating memory and sleep
(Stickgold, 2005; Tononi & Cirelli, 2006)
Learning during wake leads to LTP and as animals have evolved this level of LTP has become increasingly unsustainable
Sleep as a detachment from the environment reduces sensory input to allow learning and memory consolidation with minimal neural interference.
Complicated issue, it is easy to say sleep is related to cognition, but the details make it hard to under and the mechanisms by which sleep is important, the literature does not quantify and characterise sleep, in the same way,
– no association for one link but the association for other variables
The sleep cycle is very variable changes with:
age,
previous sleep history, psychiatric disorders medication etc.
What is the evidence for plasticity being a function of sleep
Kavanuau (2018)
fish do not sleep as a function of time awake, schooling fish schooling do not appear to sleep
reduced sensory processing required
Sleep contributes to non-declrative memory
Walker et al (2002) - motor
stickgold (2000) visual discrimination task
Mednick et al (2003) naps and recall
Evidence for delcarative memory = less clear
Ellenbogen et al (2000)
Sleep and verbal recall - sleep protects against interference
Payne et al (2005)
Sleep preferentially enhance retention of emotional aspect of memory
What does the sleep cycle vary with?
age,
previous sleep history,
psychiatric disorders
medication etc.
Which aspects of memory might be related with sleep?
translocation STM-> LTM
consolidation (stablisation/enhancement)
alternatively loss/erasure ((Crick and Mitchison, 1983)
REM sleep to remove parasitic modes of brain acitivty
rather than consolidating memories REM sleep removes them
What is the two-stage model of memory and how is it related to sleep?
• Memory is not a single entity there are declarative and non-declarative memories
• Declartive =
o Consciously recalled from the hippocampus
• Non-Declarative =
o Memories inc Motor learning
• These categories are not always distinct in a real-life situations (language learning)
• This is an issue because when talking about the relationship between sleep and memeory have to ask which aspect we want to quantify
• Many different stages of memory:
o Encoding
o Intergrting
o Traslocation
o Consolidation
Migrating from hippocampus to neocortex
Stabilisation
Enhancements
o recall
o Loss
o Reconsolidation
• The two-stage model suggests that to avoid over-writing esiitng knowledge with new information, have two seeprate memory stores with a gradual transfer from a temporary to a long-term memory
• For declarative memories these would be the hippocampus and neocortex
o Want to now how the transfer from temproy to LTM is related to sleep
Hippocampal neocortical transfer
• During wake memories are encoded in the temporary store through patterns of cotical firin, sensory information is encoded in patterns of cortical firring
• During sleep have interaction between hippocampus and cortex, over time this trace associated wih=th emory that has become endoed within tempray store with hippocampus migrate out to long term store
o Temporary store is clear – memories of recent events have transferred up to the neocortex, now have the ability to encode new information in the hipposcampus whereas memory wanted to encode is now retained in the firing pattern of cortical modules
o The behavioural disconnection is to avoid interaction from new patterns being encoded I nthe temporary store and overwittieng the patterns (memories) that are being transferred
How does the hippocampus function in sleep to encode memory?
• Hippocampal neocortical transfer
o During wake memories are encoded in the temporary store through patterns of cotical firin, sensory information is encoded in patterns of cortical firring
o During sleep have interaction between hippocampus and cortex, over time this trace associated with memory that has become encoded within tempray store with hippocampus migrate out to long term store
Temporary store is clear – memories of recent events have transferred up to the neocortex, now have the ability to encode new information in the hipposcampus whereas memory wanted to encode is now retained in the firing pattern of cortical modules
The behavioural disconnection is to avoid interaction from new patterns being encoded I nthe temporary store and overwittieng the patterns (memories) that are being transferred
Briefly describe the dual process hypothesis by which memory consolidation is linked to sleep.
The dual processes hypothesis assumes that different sleep stages serve the consolidation of different types of memories
• Specifically, it has been assumed that declarative memory profits from SWS,
o Declarative memories are encoeded via hippocampal neocorticl transfer
• consolidation of nondeclarative memory is supported by REM sleep.
• The hypothesis received support mainly from studies in humans, particularly from those employing the “nighthalf paradigm.”
o This paradigm, compares retention performance across retention intervals that cover either the early or late half of nocturnal sleep.
early sleep condition, = memory tasks in the evening and then sleep for 3– 4 h before a later recall test
late sleep condition, participants first sleep for 3 h (to satisfy the need of SWS) and then are subjected to the learning phase, followed by the late-night retention sleep.
what is the sequential processing hypothesis
The sequential
hypothesis originally assumed that in a first processing step
during SWS, nonadaptive memories were weakened and
adaptive responses were strengthened, whereas during the
second processing step during REM sleep, the adaptive
memories would be integrated and stored in preexisting
knowledge networks
