The Acquisition and Retrieval of Long-Term Memories

Learning ObjectivesFollowing 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 ProcessingCraik & 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• baby• knee• help• food• five• box• south• boat• tooth

report “boat”

Results (Craik & Watkins, 1973)

Shallow vs Deep ProcessingCraik 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

0

20

40

60

80

100

Shallow Medium Deep

Incidental

Intentional

BUT...• Despite these results, some researchers

still argue that intention to learn may exert an indirect effect on memory recall.

Intention toLearn

RehearsalStrategy

RecallAccuracy

Maintenance vs Elaboration

Why does elaborative rehearsal result in better recall than maintenance

rehearsal?

• Maintenance– New knowledge NOT connected

to existing knowledge.– Fewer retrieval paths.

• Elaborative– New knowledge connected to

existing knowledge.– More potential retrieval paths.

EXISTINGKNOW LEDGENEW

NEWEXISTING

KNOW LEDGE

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” ExampleEich 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.

– 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 Features1. Effects LTM but not working memory.2. Does not affect implicit memory.3. New skill memories are hyperspecific.

Examples of Anterograde Amnesia

• H. M.– 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 Features1. 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.

• Gradually lose more distant memories and ability to perform basic cognitive tasks (reading, basic math skills, speaking coherently).

• 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.

• Neuretic plaques

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