Neural replay, sleep and memory consolidation - week 8 (Nicholas) Flashcards
(12 cards)
Jenkins & Dallenbach (1924)
Two Ss learn lists of 10 nonsense syllables until complete mastery.
Re-tested in free recall after a varying time interval (1, 2, 4 and 8hrs) filled in with sleep or wake.
Sleeping protects against forgetting.
However, absence of interference is not the whole story: actual role for memory consolidation!
Plihal & Born (1979)
Paired associated learning
Mirror tracing
Tested the differential effect of sleep composition
Compared declarative and procedural memory
Double dissociation: declarative memory promoted by slow wave sleep; motor skills improved by REM-sleep!
The ‘sleep-first’ effect
Learning of related (‘circus-clown’) or unrelated pairs (‘cactus-brick’) using study-test cycles with feedback until 24 out of 40 correct.
After 12 hrs, better performance for the sleep group, only for unrelated pairs.
Temporal gradient a retroactive facilitation: after 24 hrs, better recall for those who slept first!
Both absence of interference and system consolidation during SWS could be behind the effect.
Neural replay
(Maquet et al. 2000; Wilson & McNaughton, 1994; Rasch et al. 2007)
Over a 24-hr period, there are privileged moments (perhaps when not much encoding is happening) during which the brain spontaneously replays to itself information recently acquired.
- Done mostly unconsciously, though some of it could reach consciousness.
- Allows other brain regions to learn the information in question.
- Slow-wave sleep (SWS) appears as a key window.
Slow-wave sleep and neural replay
According to the model of systems consolidation put forward by Born and Wilhelm (2013), during slow-wave sleep, slow oscillations occurring in neocortical regions constitutes a signal sent via the thalamus to the hippocampus to reactivate hippocampal memories. As can bee seen in Fig. 3, neocortical oscillations drive thalamo-corticol spindles, which themselves drive spindle-ripple events in the hippocampus: the alignment between levels is strong and controlled always by the troughs at the level immediately above. In nutshell, the neocortex is saying to the hippocampus: “alright, now is a good time to tell me what you know!”.
“Cuing”, Rash et al. (2007)
Cued reactivation using an odour also present during the 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 the next day.
Dumay (2018)
-Net performance (i.e., sums, %) hides the presence of two opposing forces at the item-level: forgetting (inability to recollect previous knowledge) and reminiscence (ability to access knowledge inaccessible until then).
-The usual decline in performance smaller after sleep than after wake does not mean that sleep just prevents forgetting.
-I separated out ‘maintained’ items (i.e., accessible at both the 0hr test and the 12hr retest) from ‘gained’ items (i.e., inaccessible at test, but accessible at retest).
-Sleep was found (red) to increase the probability of gaining access to previously inaccessible knowledge in both recall (Fig. a) and recognition (Fig. b), and (blue) to prevent forgetting beyond wakefulness only in recall.
-Sleep does not just stabilize memories, it makes them more accessible!
The role of sleep in false memory formation
- Relied on the Deese-Roediger-McDermott paradigm to examine the influence of sleep on memory formation and distortion.
- Ss learns 8 lists of 12 semantically related words, all strongly associated with a missing critical target. E.g., door, glass, pane, […] for WINDOW
- Overnight sleep (Fig. 1) and napping (Fig. 4) increased the number of false memories (‘critical words’). No such effect was found for mere intrusions.
Sleep strengthens associations between individual memory elements, and fills in the gaps!
Sleep-associated changes in the mental representation of spoken words
Assimilation of the novel words in lexical memory appears to occur while we sleep, as part of consolidation. (cf. Wang et al., 2017)
Free recall shows enhanced memory performance (hypermnesia) after sleep, but not after wake.
Emotional memory formation is enhanced across sleep intervals with high amounts of rapid eye movement sleep
Examined whether sleep preferentially enhances memory for emotional narratives.
Ss memorized the details of two small descriptions (incl. 94 content words): e.g. “manufacturing bronze sculptures” vs. “child murdering”.
Number of content words type-recalled was the memory measure.
Text retention, especially if content was emotional, benefitted more from late night sleep!
Sleep preferentially enhances memory for emotional components of scenes.
-Looked at the role of sleep on memory for object and background components of scenes.
-Main components either negative or neutral, whereas background always neutral.
-Sleep enhanced recognition memory for emotional components to the detriment of background details.
-No such overnight trade-off for neutral scenes!
-The amygdala, which we know encodes emotions and modulates the functioning of the hippocampus is likely to play a decisive role in this effect.
Overnight trade-off between emotional objects and background details!
Dumay (2018) - setting the alarm
-This study examined whether memory consolidation gives neutral cues the power to grab attention after they co-occurred in the context of threat. Participants learnt one set of associations between a made-up word and a neutral or emotional picture 7 days before the test, and another set on the day of test. Emotional and neutral pairs had similar learning rate (Fig. 3). Crucially, pause detection, an auditory analogue of the emotional Stroop task, that required to decide whether a short artificial silence was present anywhere in the word (presented on its own) revealed no emotion effect for same-day (i.e., unconsolidated) associations tested either immediately 0 hrs or 6 hrs after learning, but robust interference for seven-day-old (i.e., consolidated) alarming associations. Word emotional attributes hence take between six hrs and seven days to be operational.
