Memory Consolidation: Transformation

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Memory Consolidation Transformation
Collaborators Rebecca Gomez Almut Hupbach Oliver
Hardt
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EVENT
ENCODE
CONSOLIDATE
FIXED MEMORY
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EVENT
ENCODE
CONSOLIDATE
FIXED MEMORY
REACTIVATION
SLEEP
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EVENT
ENCODE
CONSOLIDATE
FIXED MEMORY
REACTIVATION
RECONSOLIDATION
UNFIXED MEMORY
PROTEIN SYNTHESIS INHIBITORS
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EVENT
ENCODE
CONSOLIDATE
FIXED MEMORY
REACTIVATION
RECONSOLIDATION
TRANSFORMED MEMORY
NEW/ALTERED EXPERIENCE
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EVENT
ENCODE
CONSOLIDATE
TRANSFORMED MEMORY
REACTIVATION
SLEEP
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Reactivation Transformation
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Reactivation Transformation
Set 2
Set 1
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Basic Design
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Reminder Updating Effect
Set 1 Items
Set 2 Items
Recall
N 12 in all groups
REMINDER
NO REMINDER
CONTROL
Hupbach, Gomez, Hardt Nadel, Learning Memory,
2007
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Immediate Recall Reconsolidation or Retroactive
Inhibition
N 12 in all groups
Hupbach, Gomez, Hardt Nadel, Learning Memory,
2007
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Source Confusion?
Absence of intrusions from Set 1 into Set 2 --
effect is asymmetrical and not simple source
confusion
Set 1 Items
Set 2 Items
N 12 in both groups
REMIND
NO REMIND
Hupbach, Gomez, Hardt Nadel, Learning Memory,
2007
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Persistence of Updated Memory Delayed
RecallMonday learn set 1Wednesday remind or
not, learn set 21 or 2 weeks later recall
either Set 1 or Set 2
The effect persists for at least 2 weeks,
suggesting it is a real change in memory
unpublished
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Persistence Delayed Reactivation1st Monday
learn set 1 2nd Monday remind, learn set
23rd Monday recall Set 1
The effect can be elicited at least a week after
initial storage of a memory
Hupbach, Gomez, Hardt Nadel, unpubl.
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What Triggers Updating?
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Reminder Effects - One Cue
N 12 in all groups
Hupbach, Gomez, Hardt Nadel, 2008.
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Reminder Effects -- Two Cues
Set 1 Items
Set 2 Items
Context Experimenter
Context Question
Question Experimenter
N 12
N 8
N 12
Hupbach, Gomez, Hardt Nadel, 2008.
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Imagining Context
Set 1 Items
Set 2 Items
N 12
Hupbach, Gomez, Hardt Nadel, unpubl.
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Conclusions re Context

• Context reminder critical to updating and
  reconsolidation
• Recall acts as another training trial, does not
  initiate update
• In episodic memory context determines whether
• new memory formed
• OR
• old memory updated
• Similar result seen in place cell remapping
  studies
• BUT, a caveat re the role of context

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Testing in a familiar context 5 year-olds at
home
Context alone fails to elicit updating in a
familiar context
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Testing in a familiar context 5 year-olds at
home
Context alone fails to elicit updating in a
familiar context
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5 year-olds tested in day-care setting
Set 1 Items
Set 2 Items
REMIND
NO REMIND
N 11
N 7
But, context alone does elicit updating in an
unfamiliar context
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Bigger Picture

• Memory is not fixed - perhaps ever
• Misinformation effect
• Hindsight bias
• Adaptive nature of memory malleability
• What then is consolidation?
• Not strengthening but transforming, assimilating

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Sleep Transformation
Study effects of sleep by exposing infants to
material prior to a nap and testing afterwards
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Design

• Toddlers exposed to material 4 hrs before lab
  visit
• (48 15-month-olds)
• Conditions (exposure to an artificial language)
• Nap
• No Nap
• Nap control
• A Minimitter actiwatch with computer driven
  chip attached to infants
  ankle and used to record body movements

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Nonadjacent dependency learning
15-month-olds Familiarized with one of two
artificial languages
Gómez (2002) Gómez Maye (2005)
vot-kicey-jic, pel-wadim-rud
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Variability manipulation
X 24
X1 X2 X3 . . . . . . . . . . . . X24

• Gómez (2002) Gómez Maye (2005)
• Nonadjacent dependencies heard equally often in
  each condition
• Difference between conditions was size of pool
  from which middle element drawn.
• Learners only track non-adjacencies when
  adjacent dependencies are sufficiently low,
• when X 24.

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Variability manipulation
X 24
X 3
X1 X2 X3 . . . . . . . . . . . . X24
X1 X2 X3
Nap control
Nap and No-nap groups
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Familiarization
15-minute incidental exposure vot wadim jic
pel kicey rud vot coomo jic vot kicey jic
pel gople rud vot fengle jic pel benez rud
pel wadim rud vot loga jic pel vamey rud
pel taspu rud pel fengle rud vot hiftam
jic.
Test
pel wadim rud vs. pel wadim jic
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Head-turn preference procedure
Infant controls the amount of exposure on any
given trial
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Veridical memory vs. abstraction

• Infants could remember specific information about
  strings themselves
• Or, could acquire a rule focusing on relationship
  between nonadjacent pairs. If so, they should
  detect nonadjacent dependencies in novel strings.
• Responses scored according to veridical memory
  and abstraction.

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Predictions

• Sleep (or delay) could change memory
  quantitatively or qualitatively
• If delay is triggering factor, nap and no-nap
  infants will perform identically
• If sleep is trigger then performance should
  differ between nap and no-nap conditions

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Naps promote abstraction!
Veridical Memory

Mean looking times (sec)
Abstraction Difference conditional on first
post-sleep trial

Gómez, Bootzin, Nadel (2006)
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What are infants learning?

• Abstraction may take form of a greater weighting
  given to relationship between first and third
  words in strings
• This weighting translates into detection of
  nonadjacent dependencies in similar (but not
  identical) strings.

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Additional questions

• Is the abstraction effect a transient one, caused
  by infants being more rested after a nap, or can
  we observed it 24 hours later before their nap?
• 15-month-olds tested 24 hrs later in Nap
  condition
• Is the abstraction effect dependent on an
  immediate nap, or like adults, will any sleep
  within a 24-hour period do?
• 15-month-olds tested 24 hrs later in No-nap
  condition

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Is the effect dependent on infants being
well-rested? No, it occurs 24-hours later before
a new nap
Veridical Memory
Mean looking time differences (sec)
Abstraction Difference conditional on first
post-sleep trial

Hupbach, Gómez, Bootzin, Nadel (in press)
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Is the effect dependent on an immediate nap? Yes.
24-hours later there was no retention in the
No-nap condition
Veridical Memory
Mean looking time differences (sec)
Abstraction Difference conditional on first
post-sleep trial

Hupbach, Gómez, Bootzin, Nadel (in press)
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Summary

• Infants in Nap and No-nap conditions were exposed
  to an artificial language 4 or 24 hours prior to
  test.
• No immediate nap Infants retained veridical
  memory over a 4-hour delay but showed no
  retention over 24 hours.
• Immediate nap Sleep facilitated abstraction 4
  and 24 hours after exposure.

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How could sleep make memory abstract?

• Sensitivity to both specific and abstract
  information initially, but weight these
  differently before and after sleep
• Forget specific details of stimulus with sleep
• Sleep protracts learning-dependent processing
  necessary for extraction of general patterns
  (OReilly Rudy, 2000 Wilson McNaughton, 1994)

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Implications

• Transformation occurring with sleep introduces
  flexibility
• Infants detected general pattern in artificial
  language whether it was instantiated exactly as
  before or not.
• Abstraction is a crucial form of memory change
  for developing learners who must retain key
  aspects of experience while generalizing to new
  information.
• Sleep appears to be instrumental in this process