Neural Replay, Sleep & Memory Consolidation

Question 1

JENKINS & DALLENBACH (1924)

Answer 1

• 2 pps learn lists of 10 nonsense syllables until complete mastery
• re-tested in free recall post varying time interval (1/2/4/8hrs) filled in w/sleep/wake
• sleeping protects against forgetting
• forgetting isn’t so much old impression decay/associations as it is interference/inhibition/obliteration of old by new
• BUT interference absence isn’t it; actual role for memory consolidation

Question 2

PLIHAL & BORN (1997)

Answer 2

• effects of early/late nocturnal sleep on declarative/procedural memory
• tested differential effect of sleep composition via paired associated learning & mirror tracing
• compared declarative/procedural memory
  RESULTS
• double dissociation; declarative memory promoted by slow wave sleep; motor skills improved by REM-sleep

Question 3

PAYNE ET AL. (2012)

Answer 3

• the “sleep-first” effect
• learning of related (circus/clown)/unrelated (cactus/brick) pairs using study-test cycles w/feedback til 24/40 = correct
• post 12h = better performance for sleep group (only for unrelated pairs)
• post 24h = temporal gradient retroactive facilitation aka. better recall for those who slept 1st
• both interference absence & system consolidation during SWS could be behind effect

Question 4

NEURAL REPLAY (RASCH ET AL. (2007))

Answer 4

• privileged moments over 24h period (maybe when not much encoding is occurring) during which brain spontaneously replays recently acquired info to itself
• done mostly unconsciously
• allows other brain regions to learn info
• slow-wave sleep (SWS) appears as key window

Question 5

SLOW-WAVE SLEEP & NEURAL REPLAY (BORN & WILHELM (2013))

Answer 5

• slow oscillations occurring in neocortical regions during slow-wave sleep constitutes signal sent via thalamus to hippocampus to reactivate hippocampal memories
• neocortical oscillations drive thalamo-cortical spindles which then drive spindle-ripple events in hippocampus
• alignment between lvls = strong & controlled always by troughs at lvl immediately above
• aka. neocortex is telling the hippocampus that now’s a good time to give relevant info

Question 6

CUEING (RASH ET AL. (2007))

Answer 6

• cued reactivation using odour also present during learning phase
• used spatial memory as skill
• re-exposure to associated odour during slow-wave sleep reactivated hippocampal areas active during learning
• also led to enhanced memory performance next day

Question 7

SLEEP x MEMORY BENEFITS

Answer 7

• makes previously inaccessible memories accessible
• promotes gist extraction
• integrates new info w/long-consolidated knowledge

Question 8

DUMAY (2018): PROCEDURE

Answer 8

• studies on sleep improving memory accessibility
• net performance (ie. sums) hides presence of 2 opposing forces at item lvl:
  1) forgetting (inability to recollect previous knowledge)
  2) reminiscence (ability to access knowledge inaccessible until then)
• protection against loss/reminiscence = measured proportionally to maximum number of items that could be lost/gained

Question 9

DUMAY (2018): RESULTS

Answer 9

• usual decline in performance aka. smaller post sleep > after wake does NOT mean that sleep “prevents” forgetting
• maintained (ie. accessible at 0h &12h retest) items separated from gained items (ie. inaccessible at test BUT accessible at retest)
• sleep increased prob of gaining access to previously inaccessible knowledge in both recall/recognition & to prevent forgetting beyond wakefulness only in recall
• aka. sleep doesn’t just stabilise memories; it makes them ^ accessible

Question 10

PAYNE ET AL. (2009): PROCEDURE

Answer 10

• relied on Deese-Roediger-McDermott paradigm to examine influence of sleep on memory formation/distortion
• pps learned 8 lists of 12 semantically related words all strongly associated w/missing critical target (ie. door/glass/pane) for window

Question 11

PAYNE ET AL. (2009): RESULTS

Answer 11

• overnight sleep/napping increased number of false memories (critical words)
• no such effect for mere intrusions
• aka. sleep strengthens associations between individual memory elements & fills the gaps

Question 12

WANG ET AL. (2017)

Answer 12

• studies sleep-associated changes in mental representation of spoken words
• assimilation of novel words in lexical memory appears to occur while we sleep as part of consolidation
• free recall shows enhanced memory performance (hypermnesia) post sleep BUT not post wake

Question 13

WAGNER ET AL. (2001): PROCEDURE

Answer 13

• examined whether sleep preferentially enhances memory for emotional narratives
• pps memorised details of 2 small descriptions incl. 94 content words (ie. “manufacturing bronze sculptures” VS “child murdering”)
• number of content words type-recalled = memory measure
• test retention (esp. if content = emotional) benefitted more from late night sleep

Question 14

PAYNE ET AL: PROCEDURE

Answer 14

• looked at role of sleep on memory for objects/background components of scenes
• main components = negative/neutral; background = always neutral
• sleep enhanced recognition memory for emotional components to detriment of background details

Question 15

PAYNE ET AL: RESULTS

Answer 15

• no overnight trade-off for neutral scenes; instead overnight trade-off between emotional objects/background details
• amygdala (encodes emotions/modulates functioning of hippocampus) = likely to play decisive role in effect

Question 16

DUMAY ET AL. (2018): PROCEUDRE

Answer 16

• examined whether memory consolidation gives neutral cues power to grab attention post co-occurrence in threat context
• pps learnt 1 association set between made-up words & neutral/emotional pic 7 days pre test; another set on test day

Question 17

DUMAY ET AL. (2018): RESULTS

Answer 17

• emotional/neutral pairs = similar learning rate
• pause detection = auditory analogue of emotional Stroop task; required to decide if short artificial silence = present in word (presented alone)
• pause detection revealed no emotion effect for same-day (unconsolidated) associations tested immediately 0hr/6hr post learning
• BUT robust interference for 7d/o (consolidated) alarming associations
• word emotional attributes hence take between 6h/7d to be operational

Question 18

SUMMARY

Answer 18

• protection against forgetting occurs at synaptic/systems lvls
• slow-wave sleep (SWS) = characterised by hippocampus not encoding & neural replay; makes it promote synaptic/systems consolidation
• synaptic consolidation in hippocampus may depend on amount of retroactive interference aka. may not be specific to sleep
• sleep not only prevents forgetting but also:
  1) helps recover info
  2) promotes fist extraction
  3) integrates new info w/existing info
• consolidation (via sleep) enhances declarative memory for alarming elements to detriment of background details
• also gives originally neutral cues power to grab attention once they’ve co-occurred w/threat