Transcript Memory Acquisition and Retrieval

The Acquisition and Retrieval of
Long-Term Memories
Learning Objectives
Following this lecture, you should be able to:
• Define the “depth of processing effect” and distinguish between
“maintenance” and “elaborative” rehearsal.
• Distinguish between “intentional” and “incidental” learning, and
understand the role of “intention to learn” in the formation of
long-term memories.
• Define “state-dependent learning” and understand the
implications of SDL for improving exam performance.
• Describe the contribution of the “memorizer” to the acquisition
of new memories.
Depth of Processing
Craik & Lockhart (1972)
• The manner in which information is
initially encoded affects how well
information will be remembered.
• Shallow vs Deep Processing
Two Common Encoding Strategies
1. Maintenance Rehearsal
– shallow processing
– repetition of information
– less effortful
2. Elaborative Rehearsal
– deeper processing
– think about meaning of information and how it
relates to existing knowledge.
– more effortful
Maintenance Rehearsal and Recall
(Craik & Watkins, 1973)
• Is recall accuracy related to the number to
times an item is repeated using
maintenance rehearsal?
• Task:
– listen to list of words
– keep track of the most recent word beginning
with “B”
– surprise memory test in which subjects must
recall all “B” words that were presented on list.
Word List
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baby
knee
help
food
five
box
south
boat
tooth
report “boat”
Results
(Craik & Watkins, 1973)
Shallow vs Deep Processing
Craik and Tulving (1975)
Noice (1991, 1992)
• Noice (1991,1992) compared the strategies
used by professional actors and novices
learn lines to a script.
• Novices
• rote memorisation
• few elaborations
• Professionals
• search for meaning of words
• search for character’s motivation
Intention to Learn
What is the effect of intention to learn on
memory recall?
Do individuals who expect their memory to be
tested perform better on memory tests than
individuals who do not expect their memory
to be tested?
Intention to Learn and DOP
Results
100
80
60
Incidental
40
Intentional
20
0
Shallow Medium
Deep
BUT...
• Despite these results, some researchers
still argue that intention to learn may
exert an indirect effect on memory recall.
Intention to
Learn
Rehearsal
Strategy
Maintenance vs Elaboration
Recall
Accuracy
Why does elaborative rehearsal result in
better recall than maintenance rehearsal?
• Maintenance
– New knowledge NOT connected to
existing knowledge.
– Fewer retrieval paths.
NEW
EXISTING
KNOWLEDGE
• Elaborative
– New knowledge connected to
existing knowledge.
– More potential retrieval paths.
NEW
EXISTING
KNOWLEDGE
State Dependent Learning
• Memory for information is improved if
the retrieval context matches the
context in which the information was
orginally encoded.
Underwater Memory Study
(Godden & Baddeley, 1975)
Results
(Godden & Baddeley, 1975)
Results
SDL “Internal State” Example
Eich et al. (1975)
SDL Explanation
• When people learn new material, they do NOT just
learn the material. They also encode information
about the physical and mental context in which the
new material was learned.
• A change in context at the time of retrieval makes
recall more difficult because contextual cues are
no longer present to aid retrieval.
The Role of the Memorizer
• Choice of encoding strategy
– automatic control
– conscious control (metamemory)
• Existing knowledge
– framework to organising and collecting
new knowledge
Physiological Basis of
Memory Acquisition
Three Brain Structures
Central to Memory
• Cortex
• Cerebellum
• Hippocampus
Synaptic Changes and Memory
• Neurotransmitter Changes
– increase in neurotransmitter
released by pre-synaptic neuron
– increase in receptors at
postsynaptic neuron
• Structural Changes
– development of new dendrites or
axon terminals
– Formation of new synapses
Cerebral Changes Resulting from Training
• Rats randomly assigned to one of 3
conditions (25 days after birth)
– Standard Condition
– Impoverished Condition
– Enriched Condition
• Brains dissected after approximately 80
days.
Results
• Rats in the enriched condition had
significantly heavier cortices than
those in the impoverished condition.
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Larger cell bodies
Longer dendritic branches
More dendritic spines
More synaptic contacts
Memory Disorders
• Amnesia
• Korsakoff’s Syndrome
• Alzhiemer’s Disease
Amnesia
Definition: A partial loss of memory
usually caused by brain trauma.
– Anterograde
– Retrograde
– Korsakoff’s Syndrome
Anterograde Amnesia
• Inability to form new long-term
explicit memories following brain
damage.
• Main Features
1. Effects LTM but not working memory.
2. Does not affect implicit memory.
3. New skill memories are hyperspecific.
Examples of Anterograde Amnesia
• H. M.
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Scoville & Milner (1957)
severe epileptic seizures.
bilateral excision of hippocampus.
exhibited both anterograde and
retrogade effects.
• Jeremy Video
Retrograde Amnesia
• Memory loss for events prior to brain
injury.
• Main Features
1. Affects primarily episodic memory, but not
semantic or implicit memory.
2. Time span for memory loss varies considerably
across cases.
3. Permanence of memory loss varies across
cases.
Korsakoff’s Syndrome
• Severe memory disruption caused by
chronic alcohol abuse.
• Anterograde amnesia
• Retrograde amnesia
• Confabulation
• Linked to thiamine deficiency
• Post-mortem examinations reveals
damage to diencephalon (thalamus and
hypothalamus) but not hippocampus.
Alzheimer’s Disease
Disease Progression
•
Forget information from recent past.
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Gradually lose more distant memories and ability
to perform basic cognitive tasks (reading, basic
math skills, speaking coherently).
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Lose motor coordination, unable to control
bodily functions, recognise loved ones.
Neurophysiological Basis
• PET scans - marked reduction in CBF to
posterior parietal cortex and temporal
lobe.
• Autopsies - diffuse degeneration of tissue
in cerebral cortex, and hippocampus.
• Microscopic studies - cellular abnormalities
such as neurofibrillary tangles, senile
plaques, and the presence of -amyloid.
Causes??
Fragmented amyloid proteins
– ApoE Gene - two copies of ApoE4
substantially increases risk of
Alzhiemer’s.
– Environmental toxins - aluminium
The Role of Neurotransmitters
• Acetylcholine
– blocking AcH -> anterograde amnesia
– increasing AcH -> improves memory
• Hints for Alzheimer’s disease
– brain grafts using fetal tissue
– Reagan moratorium