Memory Consolidation

Question 1

CONSOLIDATION FORMATS

Answer 1

CELLULAR
- synaptic
SYSTEM-LVL
- whole brain

Question 2

DEFINTION

Answer 2

• offline neural changes that lead to memory stabilisation/enhancement/integration w/pre-existing knowledge

Question 3

MUELLER & PILZECKER (1900): SS

Answer 3

• SS learnt paired-associate syllables list (AB); tested in cue recall using 1st syllable (A)
• interpolating another list (CD) impaired memory of first list (AB)
• found temporal gradient (the closer in time interfering list is introduced w/target list, the stronger its amnestic effect)

Question 4

MUELLER & PILZECKER (1900): MENTAL EXERTION

Answer 4

• memories require time to consolidate
• retroactive interferences compromises integrity of recently formed BUT not yet consolidated memories
• interference = nonspecific (aka. interfering material doesn’t have to be similar to target material (AB vs CD)
• mental exertion = interfering force

Question 5

WIXTED & CAI (2014): THE CLAY SCULPTURE METAPHOR

Answer 5

• new memories = initially fragile BUT soon become resistant to interference
• aka. show less potential for damage

Question 6

WIXTED (2004): SHAPE OF THE FORGETTING FUNCTION

Answer 6

• clay metaphor (aka. memories become more resistant to interference) fits well w/forgetting curves
• rate w/which we forget is NOT constant
• this would be exactly the property of memoryless systems

Question 7

WIXTED (2004): SHAPE OF THE FORGETTING FUNCTION (FURTHER EVIDENCE)

Answer 7

EBBINGHAUS (1885)
- forgetting function = we forget less as time goes
JOST (1897)
- if 2 memories have = strength BUT dif ages -> older trace decays at slower rate
- this continuous reduction to forgetting rate = consolidation sign

Question 8

CELLULAR CONSOLIDATION

Answer 8

• occurs at neuron lvl (not at whole-brain systems lvl)
• takes place during 1st hours/days post initial memory formation in hippocampus
• fits well w/idea of trace-hardening physiological process put forward w/Mueller & Pilzecker
  BLISS & LOMO (1973)
• corresponds to discovery of long-term potentiation

Question 9

BLISS & LOMO (1973): LONG-TERM POTENTIATION

Answer 9

• long-lasting enhancement of synaptic efficacy induced by tetanus (short high-frequency stimulation burst) to presynaptic neuron

Question 10

RETROGRADE FACILITATION

Answer 10

• if subsequent encoding (mental exertion) interferes w/memory consolidation -> factors blocking new encoding should promote memory stabilisation
• examples include:
  1) alcohol (DUMAY ET AL. (2017))
  2) benzodiazepines (WEINGARTNER ET AL. (1995))
  3) slow-wave (non-REM) sleep (YAROUSH ET AL. (1971))
• resulting anterograde amnesias were accompanied by retrograde facilitation
• aka. memories formed prior to drug intake/sleep = forgotten to lesser degree > prior to placebo/wake

Question 11

SYSTEMS CONSOLIDATION

Answer 11

declarative memories becoming independent from hippocampus & ^ dependent on neocortex
- HM’s bilateral medial temporal lobe (MTL) resection:
1) anterograde amnesia (inability to form new declarative memories aka. “what”)
2) temporally graded retrograde amnesia (impairment of memories formed prior to surgery; stronger for new VS old memories aka. Ribot’s law (1881))

Question 12

TEMPORAL GRADIENT OF SEMANTIC MEMORY

Answer 12

BEHAVIOUR (BAYLEY ET AL. (2006))
- 6 amnesic patients w/damaged limited to hippocampal region
BRAIN ACTIVATION IN CONTROLS (SMITH & SQUIRE (2009))
- 160 qs on news events over 30ys
SAME OVER 24H (TAKASHIMA ET AL. (2009))
- systems consolidation can occur v quickly
- richness of memorised materials may determine how fast systems consolidation occurs

Question 13

ACTIVATION SHIFT FROM MEDIAL-TEMPORAL LOBE -> NEOCORTEX: SIGNIFICANCE

Answer 13

• fragments of declarative memories stored in neocortex from outset (ie. sensory/semantic areas) as they travel through
• hippocampus acts as relay station; binds fragments together
• cortico-cortical associations develop over time so memories become independent of hippocampus

Question 14

COMPLEMENTARY LEARNING SYSTEMS (MCCLELLAND ET AL. (1995))

Answer 14

1) fast learning system holding info only temporarily (medial temporal lobe ie. hippocampus)
2) slow learning system that serves as long-term store (ie. neocortex)
MAIN IDEA
- info initially stored in hippocampus = progressively fed back into neocortex via “neural replay” so pre-existing knowledge can accommodate newly learnt info
- hippocampus = internal sparring partner of neocortex
- both systems used to encode new learning so reactivation/redistribution has to occur offline (ie. during sleep)