// Sleep and memory Flashcards
The sleep effect
Jenkins 1924
Learning followed by sleep leads to better recall than learning followed by wake
Theories for how sleep aids memory
- Interference, decay and consolidation
- ASE model
- System consolidation
- Replaying memories
- Replaying schemata
- Insight
- Memory triage
- Time between recall and learning
- Sleep duration
Interference, decay and consolidation
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
ASE model
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
System consolidation
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)
Replaying schemata
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
Insight
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
Memory triage
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
Time between learning and recall
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
Sleep duration
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
NREM is more important for memory
Ekstrand 1977
Retention better after SWS than after REM, worse after wakefulness
REM is more important for memory
summary
- General memory
- Emotional memory
- Visual memory
- Procedural memory
- Cognitive flexibility
- REM augmentation
- Dreams and memory
- Flexible processing
- Neurochemical balance
REM and general memory
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
REM and emotional memory
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
REM and visual memory
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