Unit 3 - Memory

Unit 3 - Memory

What we’ve learnt so far

Memory dot points…Key knowledge• mechanism of memory formation:

– role of the neuron in memory formation informed by the work of E. Richard Kandel

– roles of the hippocampus and temporal lobe

– consolidation theory

– memory decline over the lifespan

– amnesia resulting from brain trauma and neurodegenerative diseases including dementia and Alzheimer’s disease

• comparison of models for explaining human memory:

– Atkinson-Shiffrin’s multi-store model of memory including maintenance and elaborative rehearsal, serial position effect and chunking

– Alan Baddeley and Graham Hitch’s model of working memory: central executive, phonological loop, visuo-spatial sketchpad, episodic buffer

– levels of processing as informed by Fergus Craik and Robert Lockhart

– organisation of long-term memory including declarative and episodic memory, and semantic network theory

• manipulation and improvement of memory:

– forgetting curve as informed by the work of Hermann Ebbinghaus

Encoding, storage and retrieval

• Memory is an information processing system that receives, stores, organises, alters and recovers information.

• Encoding: Incoming sensory information is converted into a form that can be stored and represented in the memory system.

• Storage: The retention of information over time.• Retrieval: The process of locating and

recovering the stored information from memory.

• mechanism of memory formation:– role of the neuron in memory formation informed by the work of E. Richard Kandel

• Eric Richard Kandel, an Austrian-born American psychiatrist and neuroscientist, identified changes in the structure and functioning of neurons in the brain when forming the memory of a newly learned experience.

• Kandel’s studies with Aplysia involved using a very thin electrode (or ‘probe’) to mildly stimulate a part of the body called the siphon. The siphon is like a tail and the stimulation caused it to reflexively contract. An Aplysia would also immediately withdraw its delicate gill in case whatever shocked its siphon also shocked the gill. If Kandel did this again a moment later, an Aplysia would withdraw its gill even more quickly.


According to Kandel (2001), when Aplysia acquire a new memory through repeated

stimulation, significant changes occur in neurons involved in the process.

One change that occurs is in the way the slug’s neurons function. There is an increase in the amount of the neurotransmitter produced and released by the neurons; that is, the specific chemical substance used by neurons to communicate.

A second change that occurs is in the structure of the slug’s neurons. Neurons are interconnected by extensions, or ‘branches’, at either end called axons (which send the message)and dendrites (which receive the message). The number of these branches increases as they become ‘bushier’ through the growth of smaller ‘offshoots’ (called dendritic spines), thereby strengthening the connections between the neurons.


A third change involves the synapse. A synapse is the small space between the axon of one neuron and the dendrite of another, and neurons communicate by sending neurotransmitters across these synapses. When a memory is formed, new synaptic connections form (called synaptic growth) and this has the effect of further strengthening the connections between the neurons, making it easier for them to transmit to each other the next time. The more the neurons in a circuit are activated through use, the ‘easier’ it becomes for information to travel through the circuit.

Collectively, these changes are called longterm potentiation. Long-term potentiation (LTP) refers to the longlasting strengthening of synaptic connections of neurons resulting in the enhanced functioning of the neurons.

• mechanism of memory formation:– roles of the hippocampus and temporal

lobe

The Medial temporal lobe is the inner area of the temporal lobe. It includes the hippocampus and the amygdala

In 1953, Henry Molaison suffered severe seizures. As a means of treating them, his medial temporal lobes were surgically removed. While the surgery helped lessen the number and severity of seizures, he had the following memory problem:

• While he could remember events before the surgery, he could not develop any new episodic or semantic memories.

• His short term memory remained mostly unchanged, and psychologists concluded that this case showed evidence for the role of the hippocampus and medial temporal lobe in the formation of Long Term Memory.

• Suggests it takes approximately 30 minutes for a new memory to be transferred from STM to LTM.

• It is thought that a physical change takes place in the brain when a new memory is being made.

• If this stage is interrupted, info may be lost.

• Info must have time to ‘set’ before it is permanently stored in LTM

• mechanism of memory formation:– Consolidation theory

• A neurodegenerative disease is a disease characterised by a progressive decline in the structure, activity and function of brain tissue.

• Essentially, neurons within the brain tissue (‘neuro’) gradually become damaged or deteriorate (‘degenerate’) and lose their function.

• With neurodegenerative diseases, the gradual deterioration is typically age-related.

• mechanism of memory formation:– amnesia resulting from brain trauma and

neurodegenerative diseases including dementia and Alzheimer’s disease

• Amnesia is the loss of memory, either partial or complete, temporary or permanent. Brain trauma caused by either an inflicted or acquired head injury commonly results in some kind of amnesia.

• Anterograde amnesia is when brain damage causes loss of memory only for information or events experienced after the person sustains brain damage

• Korsakoff’s syndrome develops from alcohol related brain damage, and can develop in a space of days. Sufferers have relatively normal IQ’s, however, many people with the disease have anterograde amnesia and therefore have difficulty with or an inability to form new memories. Nor do they tend to be aware that they have memory problems.



• Retrograde amnesia is the condition where brain damage affects memory for information or events experienced before the person sustains the damage

• The memory loss may extend back a few moments, days, weeks or sometimes years. Retrograde amnesias are usually of a temporary nature and are often caused by a blow to the head.

• Dementia is an umbrella term used to describe a variety of symptoms of a large group of illnesses or neurodegenerative diseases that cause a progressive decline in a person’s mental functioning.

• The most common symptom is serious loss of mental capacity, including memory loss, a decline in intellectual ability, poor judgment, poor social skills and abnormal emotional reactions. It is often described as progressing in stages, with memory loss typically being one of the first signs of its onset. Memory loss is persistent and progressive as the dementia progresses, not just occasional.



• Alzheimer's disease is a neurodegenerative disease characterised by the gradual widespread degeneration of brain neurons, causing memory loss, a decline in cognitive and social skills, and personality changes.

• Currently Alzheimer’s disease is the fourth largest cause of death in Australia.

• Postmortems of people with Alzheimer’s disease show that the brain has the appearance of having ‘rusted’.



Atkinson-Shiffrin’s multi-store model of memory including maintenance and elaborative rehearsal,

serial position effect and chunking

Stage Function Capacity Duration

Sensory Memory

(SM)

Receives sensory info

Unlimited 1/3 – 4 secs

Short term memory

(STM)

Receives info from STM & LTM

7 +/- 2 pieces of info

18 – 20 secs

Long term memory

(LTM)

Stores info encoded from STM

Unlimited Potentially permanent

• All sensory info is retained in its original form for a very short time.

• We are not consciously aware of all of the info that enters our SM.

• We select the info that will be attended to and transferred to STM.

• Iconic memory: holds an exact replica of visual info (an icon). Duration: 1/3 – ½ sec.

• Echoic memory: holds an exact replica of auditory info (an echo). Duration: 3-4 secs.

Atkinson-Shiffrin’s multi-store model of memory including maintenance and elaborative rehearsal, serial

position effect and chunking

Sensory memory

• STM is our most active memory system that stores a limited amount of info over a short period of time.

• Duration = 18-20 secs• Capacity = 5-9 pieces of info (7+-2)• The duration of STM can be extended through

maintenance rehearsal (repetition)• The capacity of STM can be extended through

chunking (grouping info together eg. 51427496 (8 items) 51 42 74 96 (4 items).

• Elaborative rehearsal connects new info in a meaningful way with info already stores in LTM.

Short term memory



Long Term Memory - LTM

• Is a relatively permanent memory system that holds vast amounts of info indefinitely.

• Memories are organised into categories.

• Two main types of LTM – procedural & declarative (episodic & semantic).



• Evidence that STM and LTM are separate storage systems comes from the serial position effect.

• When participants are asked to recall a list of words in order, a pattern is evident.

• Words at the beginning and the end of the list are easily recalled. However words in the middle appear to get lost.

• When words at the beginning of the list are recalled easily it is known as the Primacy effect.

• When words at the end of the list are recalled easily, it is known as the Recency effect.

• Psychologists believe that items at the beginning of the list have been rehearsed and retained in LTM whereas items at the end of the list are stored in STM.

• Produces a ‘U’ shaped graph.



Types of LTM

Type Definition Example

Procedural Memory of actions & skills. ‘How to do something’

Riding a bike

Declarative Facts or events that can be brought to mind.

Describing your favourite movie to a friend.

-Episodic

-Semantic

Memory of specific events or personal experiences

Info/facts we have about the world.

The events of a party you attended on the weekend.

Knowing there are 12 months in a year.


Organisation in LTM

• Info is stored in categories that contain many links to other clusters of info.

• Semantic Network Theory – Proposes that info is organised systematically in the form of overlapping networks that are interconnected and interrelated.

• Each concept (called a node) is linked to other nodes, therefore when we retrieve info from one node, others are activated.

• Specific characteristics are stored at each node.


• Baddelely suggested that there is a part of STM called working memory that processes the info we need for dealing with the immediate moment.

• Baddeley proposed that working memory had the following sub-systems:

- The phonological loop (auditory information)

- Visuo-spatial sketchpad memory (visual information)

- Episodic buffer (allows the other components of working memory to interact with long term memory)

- The central executive (integrates information from verbal and visual storage systems – organises which issues deserve attention).

Alan Baddeley and Graham Hitch’s model of working memory: central executive, phonological loop, visuo-

spatial sketchpad, episodic buffer

• Craik and Lockhart’s levels of processing framework proposes that the level, or ‘depth’, at which we process information during learning determines how well it is stored in LTM.

• Deep processing is considered to be information that is processed based on it’s meaning.

• Deep processing could involve:• Make sure you understand the new information by restating it in your own words.• Actively question new information.• Think about the potential applications and implications of the material.• Relate the new material to information you already know, searching for connections

that make the new information more meaningful.• Generate your own examples of the concept, especially examples from your own

experiences.

• These types of mental activities involve elaborative rehearsal, thereby promoting deeper processing and enhancing your memory for new information.

levels of processing as informed by Fergus Craik and Robert Lockhart

manipulation and improvement of memory:– forgetting curve as informed by the work of

Hermann Ebbinghaus

50 % of memory loss occurs within the first hour after learning.

Ebbinghaus’s forgetting curve suggested that forgetting occurs rapidly after learning and then slowly declines over time.

The Forgetting Curve shows the rate and amount of forgetting over time.

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Unit 3 - Memory