The A cquisition 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 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

BUT... Despite these results, some researchers still argue that intention to learn may exert an indirect effect on memory recall.

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.

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. –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. –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. 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