Download Memory systems

Memory systems
Off-line processing, consolidation,
and interference
Instructions and motor learning
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Green and Flowers (1991)
Wulf (1997)
Verdolini-Marston & Belota (2003)
Boyd & Winstein (2004)
Purpose
• “Complex” skill learning (i.e. real learning)
– Occurs in context of both explicit and implicit
processes
– Trying to understand the interactivity of the two
systems in learning
Two views of interaction
• Independent
– Explicit memory arises from “witnessing” implicit
learning and does not assist it
– The different systems emerged from different
origins
• Integrated
– Explicit memory is a necessary part of acquiring
implicit memory
– Explicit memories are transformed into implicit
Method
• Provide explicit instruction, learn implicit task
– Integrated – explicit should help
– Independent – should have either no effect or hinder
learning
• Serial interception sequence learning
– http://reberlab.psych.northwestern.edu/SISL/v0.2.0/SISL.html
• Like a continuous version of the classic sequence
learning task
– Guitar hero!
• 12 item repeating sequence
Task
• “catch” the balls using the appropriate keys
Method
• 2 groups –
– Explicit:
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memorize the sequence
Watch the balls drop without hitting keys
Print out of sequence visible as they watch
Self-paced
– Implicit – none of the above
– All:
• 24 random cues for familiarization
• 6 X 480 learning trial blocks (384 sequenced, 96 novel)
• 540 trial test block
– 3 different sequences – I from practice
– 5 reps per sequence (60 trials)
– Used to show performance diffs due to learning
Method
• Following practice:
– Explicit recognition test
• 5 different sequences have two reps each
• Rated confidence that sequence was the one practiced
– Explicit recall task
• Try to produce sequence using keys without balls being
seen
Results
• No group differences in performance or
learning
Results
• Differences in explicit recall…
Only statistical difference – explicit
group could produce the sequence
better than the implicit group
Conclusions
• Independent, multiple memory systems ideas
are better supported
– This provides direct evidence against the
integrated, single system argument
– Implicit learning here is not aided by explicit
knowledge
– …but it’s not hurt either (unlike earlier studies)
– Task specific issues?
• Is this learning coordination?
Historically…
• H.M.
• Squire & others (e.g. Cohen and Squire 1980)
– Declarative and procedural memory systems are
independent
• Alzheimer’s: declarative impaired, procedural not
• Huntington’s: procedural impaired, declarative not
• fMRI scanning: procedural & declarative “work” lights
up different neural circuitry
New evidence…
• Willingham (1997)
– Activity within medial temporal lobe and striatum
associated
• Brown and Robertson (2007a and b)
– Learning word list after motor skill impairs motor
skill
– Learning motor skill after word list impairs word
learning
Interference paradigm
• Consolidation and reconsolidation…
– Susceptibility to interference, and time:
Lines of evidence…
• A shared resource?
– Medial temporal lobes active during both
declarative and procedural processing.
• Coupling causing shift from independence?
– Damage to frontal lobe prevents interference
– Wakefulness vs. sleep – dorsolateral prefrontal
cortex invoked when awake but not when asleep
• Seems to be that frontal lobe makes MTL and Striatum
interfere
Interference possibilities & findings
Role of dorsolateral prefrontal cortex…
Function of interference…
• When learning motor skill first…
– Interference prevented by stimulating motor
cortex
• Neither memory impaired or enhanced when
interference prevented
– Interference independent of memory processing
– Stimulated areas (DLPFC, M1) seem to be
producing the interference…why?
Function of interference…
• Why?
– New memories are unstable at time of learning
– Retrieved memories are unstable when recalled
• Maybe instability of both makes for better
reorganization of the paired memories?
– DLPFC or M1 may
• Exert executive control over memory
• Select memories susceptible to interference
Brain state & processes
• Areas of brain interfere when awake, but not
when asleep
– When awake, memories are organized interactively
– When asleep they are organized independently
• Learning…
– Independent acquisition but interactive after
learning?
• Aging
– DLPFC function alters with age. Youth – mature – old.
Manipulating interference
• Altered sequence of learning to avoid
interference?
– Maybe, but what’s the function of the
interference?
– Maybe it leads to greater memory integration?
Memory stability
• New memories become resistant to
interference over a few hours.
– Circuits effecting this change depend on type of
practice…
• Single block – M1
• Multiple blocks – DLPFC
– “Offline” processes stabilize learning.
Offline learning
• Can be enhanced by
– Sleep (motor learning 20-30%)
– Praise
– Cues at encoding
• Learning & consolidation (offline learning) rely
on similar brain areas and chemical processes
– Circuitry in bird song similar when actually singing
and when dreaming.
Retrieval and stability
• Retrieved memories can be interfered with
– But only when new information is to be paired
with retrieved information
– Possible link with need to integrate new with old
memory