// Sleep and memory Flashcards

1
Q

The sleep effect

A

Jenkins 1924

Learning followed by sleep leads to better recall than learning followed by wake

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2
Q

Theories for how sleep aids memory

A
  1. Interference, decay and consolidation
  2. ASE model
  3. System consolidation
  4. Replaying memories
  5. Replaying schemata
  6. Insight
  7. Memory triage
  8. Time between recall and learning
  9. Sleep duration
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3
Q

Interference, decay and consolidation

A

Ekstrand 1977

Interference

  • behavioural - simplest theory
  • fewer events interfere with the memory during sleep

Decay

  • Happens slower during sleep

Consolidation

  • aided by lack of interference and decay
  • sleep actively improves memory
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4
Q

ASE model

A

Walker 2005

How memories become long-term during sleep

  • acquisition - memory can be recalled in the short-term
  • stabilisation - lack of interference over time
  • enhancement - interconnection of the memory with others in the LTM

Points 2 & 3 are consolidation

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5
Q

System consolidation

A

Diekelman 2010

  • fast rate learning - temporary store
  • slow rate learning - long-term store
  • memories gained in slow rate learning are strengthened over time
    • reactivation and consolidation during SWS avoids interference and altered synapses during REM
    • integrates memories into LTM store
    • promotes extraction of repeating features to form schemata
  • evidence for reactivation - cues present in learning and sleep = stronger consolidation
    • Lee 2002 - rat place cells in hippocampus that fire when learning a maze also fire during SWS - replaying the memory. Mixed up during REM - triggers abstraction (form schemata)
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6
Q

Replaying schemata

A

Lewis

  • schemata are replayed during sleep, not single memories
  • abstraction = extraction of repeating features to create an abstract gist for all similar situations (schemata)
  • DRM Paradigm = more likely to form false memories during sleep bc gist is processed rather than specific details
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7
Q

Insight

A

Wagner 2004

  • calculate final number in a series
  • complex but can be done simply once insight into the method is gained
  • more likely to gain insight after sleep
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8
Q

Memory triage

A

Stickgold 2013

  • Selective processing of valuable info
  • Told after learning they’ll be tested on certain lists/get monetary rewards for remembering certain lists = higher consolidation of these lists
  • Rijn 2017 – triage for personal, non-reward-related valuable info
    • Learn 14 welsh words
    • Cued recall – given welsh, asked for English
    • Better recall after sleep
    • Better recall for those who value the Welsh language more
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9
Q

Time between learning and recall

A

Stickgold 2001

Experiment 1

  • visual discrimination task
  • test after 2, 5, 11 hrs - little difference
  • test after 9, 13, 22 hrs including 7hrs sleep - improved performance

Experiment 2

  • test on same day as learning = no improvement
  • more night sleep = more improvement but little difference after 4th night
  • no improvement if no sleep on first night - initial night’s sleep is the beneficial part!
  • improvement related to SWS in first quarter and REM in last quarter of sleep
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10
Q

Sleep duration

A

Tucker 2009

  • 3.5hr naps and 7.5hr sleep improves declarative and motor memory
  • longer stage 2 improves procedural task speed
  • intelligence correlates with test performance on both tasks but not with sleep-related changes
    • intelligence doesn’t influence sleep’s effect on memory
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11
Q

NREM is more important for memory

A

Ekstrand 1977

Retention better after SWS than after REM, worse after wakefulness

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12
Q

REM is more important for memory

summary

A
  1. General memory
  2. Emotional memory
  3. Visual memory
  4. Procedural memory
  5. Cognitive flexibility
  6. REM augmentation
  7. Dreams and memory
  8. Flexible processing
  9. Neurochemical balance
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13
Q

REM and general memory

A

Fishbein 1970

  • REM deprivation leads to fragile memory
  • Others argued it’s the stress of REM deprivation
  • Oniani 1987 – woke animals gently from REM, no fragile memories

Tilly 1978

  • REM deprivation –> poorer story recall than N3 deprivation
  • Less deterioration of recall accuracy following REM recovery than N3 recovery
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14
Q

REM and emotional memory

A

Wagner 2001

  • Learn emotional or neutral short story
  • Enhanced memory for emotional texts after REM compared to SWS
  • Goes beyond behavioural theory – two sleep types giving different results

Walker 2009

  • Seen in the 80s, people with PTSD are more likely to have sleep apnoea
  • Explained that people with sleep apnoea are less able to process trauma during sleep bc of disruption so are more likely to go on to develop PTSD
  • Suggests similar for mood and anxiety disorders
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15
Q

REM and visual memory

A

Karni 1994

  • Visual discrimination task – identify whether rotated dashes are aligned horizontally or vertically
  • REM sleep only –> improved performance
  • SWS only –> poorer performance
  • Regular sleep –> improved performance
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16
Q

REM and procedural memory

A

Walker 2002

  • Finger tapping (type 4-1-3-2-4 on keyboard)
  • Performance improved by sleep
17
Q

REM and cognitive flexibility

A

Walker 2002

  • Ps woken from REM sleep solve more anagrams correctly than those woken from NREM
  • Brain engaged in more flexible cognitions during REM that continued into wakefulness
18
Q

REM augmentation

A

Solodkin 1995

  • Increased REM density and number of REMs during later REM sleep in students preparing for exams
  • “REM windows” – specific REM periods later in sleep that are better for memory consolidation
19
Q

Dreams and memory

language learning

A

DeKoninck 1990

  • People on a 6-week French course who made significant progress experienced:
    • Increased REM %age
    • French incorporated into dreams
    • Increased verbal communication in dreams
  • ☹ unsure if dreaming of what they learned has a function or is just a reflection of attained knowledge
20
Q

Dreams and memory

Spatial memory

A

Wamsley 2010

  • Virtual maze navigation – spatial memory
  • Sleep = improved vs. no sleep
  • Dream of task = biggest improvement
    • Dreams related but not copies e.g. different mazes
    • Improved consolidation
  • ☹ those who dreamed were initially worse at the task – simply more room for improvement?
  • Cognitive replay effect – longer sleep = more abstract representation of task in dreams
21
Q

REM and flexible processing

A

Stickgold 1988

  • lexical decision task with weak or strong primes
  • weak primes had stronger effect than strong primes if P woken from REM
  • suggests REM prioritises making connections we don’t make in wakefulness
    • part of memory consolidation
    • could explain bizarreness of dreams
22
Q

Neurochemicals during REM

A
  • REM links memories by processing them out of order and finding similarities between them
  • Acetylcholine aids memory linking
  • Cortisol later in the night disrupts memories
  • Dorsolateral prefrontal cortex (rational thinking) is less active during REM