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Prof. Stephan Anagnostaras

Lecture 6: Multiple Memory Systems: Implicit Memory

Neurobiology ofLearning and Memory

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Different types of learning & memory rely on different brainstructures

Explicit memoryImplicit memory

Facts(semantic)

Events(episodic)

Medial temporal lobe; diencephalon

Procedural memory:skills & habits(basal ganglia) Skeletal musculature

(cerebellum)

Classical conditioning

Emotional Responses(amygdala)

Priming(neocortex)

Eyeblink conditioning inrabbit

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Squire’s Taxonomy of Memory

Squire & Zola, PNAS, 1996

Implicit memory is a broaderterm than explicit memory

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Basal Ganglia• Can examine Parkinson’s & early Huntington’sDisease

• no apparent amnesia (declarative memory ok)

But implicit memory problems in“procedural memory”• Perceptual-Motor Learning• Habits• Skills

Separate from motor disorders

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Serial Reaction Time (SRT) Task

Subjects are not told about the sequence.

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SRT Results

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Several perceptual motor tasksimpaired by basal ganglia damage

• Serial Reaction Time

• Backwards Reading

• Prism adaptation

• Mirror drawing

• Also more cognitive tasks…

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Knowlton, Mangels, & Squire, Science, 1996

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Artificial Grammar Learning

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Prototype Abstraction

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Basal ganglia

• Implicit learning deficits in several tasks

• Don’t need a motor component

• Can be quite “cognitive”

• No explicit memory necessary

• What about animals?

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Packard, Hirsch & White,J Neurosci 1989

McDonald & White, BehNeurosci 1993

% correct

Time spent

3

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Win-Stay Acquisition Trials

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Double dissociation paper:Electrolytic lesions on win-stay

Packard, Hirsh & White, J Neurosci, 1989

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Win-Shift Training

Training Phase

Baited

Delay

Testing Phase

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Double dissociation paper:Electrolytic Lesions on win-shift

Packard, Hirsh & White, J Neurosci, 1989

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Triple D Histology (HPC + DLC)

McDonald & White, Behav Neurosci, 1993

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Triple D: Neurotoxic DLC lesionsimpair win-stay learning

McDonald & White, Behav Neurosci, 1993

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Triple D: Neurotoxic DLC lesions sparewin-shift learning

McDonald & White, Behav Neurosci, 1993

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Triple D: Neurotoxic HPC lesionsimpair win-shift learning

McDonald & White, Behav Neurosci, 1993

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Triple D: Neurotoxic BLA lesionsimpair conditioned cue preference

McDonald & White, Behav Neurosci, 1993

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Proposed characteristics of habitlearning

Squire, 1992:

• Knowledge expressed through performance, rather than recollection• Associations acquired across many trials• Less flexible (less transferable) than declarative learning

Salmon & Butters, 1995: “Habit learning refers to the formation of simple associations in which a neutral stimulus comes to elicit a certain motor response as a function of repeated reinforcement.”

Mishkin et al., 1984:Product of processing is “not cognitive information, but a non-cognitive simulus-response (S-R) bond…what is stored is not objects, emotions…but the changing probability that a given stimuluswill evoke a specific response due to the reinforcement contingencies at that time”

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Sage & Knowlton, Beh Neurosci, 2000US Devaluation of Win-Stay

US Devaluation(Testing the hypotheses)

Protocol: Train

US devaluation

Test

• If performance does not involve representation of US, the CR should remain intact (e.g., accurate, fast) on test. This would be consistent with an S-R view.

• If performance mediated by representation of US, then recall of devalued US should change the CR (e.g., inaccurate, slow) on test

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Devaluation following win-stay acquisition

ControlUnpairedPaired

Trial

Corr

ect (

%)

0

20

40

60

80

100

1 5 10 15 20 22 Probe5

Acquisition

5

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0

20

40

60

80

100

Corr

ect (

%)

1 2 3 4 5 6 7 8 Trials within Post-CTA

Extinction Probe

A. Extinction Accuracy

ControlUnpairedPaired

Win-stay late timepoint post-CTA trials

xx

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Post-CTA win-stay accuracy summary

Timepoint(Amount of Training)

2, 9, or 22 days

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Post-CTA win-stay latency summary

Timepoint(Amount of Training)

* = significant difference

* *

*

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Contextual Cuing Task(Chun & Phelps, Nat Neurosci, 1999)

Easy Version Difficult Version

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Contextual Cuing Task(Chun & Phelps, Nat Neurosci,1999)

Implicit Learning Deficit in Amnesia !

Amnesics2 anoxic (1 conf hipp)2 encephalitic (2 conf hipp)

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Memory systems in Implicit Memory

• Not all implicit memory is independent ofthe hippocampus

• Not all implicit memory depends on thebasal ganglia, e.g., emotional learning,priming, certain motor responses

• Cortical systems (e.g., priming)• Amygdala (fear conditioning)• Cerebellum (eyeblink conditioning)…etc