Unit 3 - Memory
What we’ve learnt so far
Key knowledge
Memory dot points…
• 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.
– role of the neuron in memory formation
informed by the work of E. Richard Kandel
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.
– role of the neuron in memory formation
informed by the work of E. Richard Kandel
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.
• mechanism of memory formation:
– Consolidation theory
• 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:
– amnesia resulting from brain trauma and neurodegenerative
diseases including dementia and Alzheimer’s disease
• 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.
• mechanism of memory formation:
– amnesia resulting from brain trauma and neurodegenerative
diseases including dementia and Alzheimer’s disease
•
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.
• mechanism of memory formation:
– amnesia resulting from brain trauma and neurodegenerative
diseases including dementia and Alzheimer’s disease
•
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
Sensory
Memory
(SM)
Short term
memory
(STM)
Long term
memory
(LTM)
Function
Capacity
Duration
Receives
sensory info
Unlimited
1/3 – 4 secs
Receives info
from STM &
LTM
7 +/- 2 pieces of
info
18 – 20 secs
Stores info
encoded from
STM
Unlimited
Potentially
permanent
Atkinson-Shiffrin’s multi-store model of memory including
maintenance and elaborative rehearsal, serial position effect
and chunking
Sensory memory
• 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
Short term 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.
Atkinson-Shiffrin’s multi-store model of memory including
maintenance and elaborative rehearsal, serial position effect
and chunking
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).
Atkinson-Shiffrin’s multi-store model of memory including
maintenance and elaborative rehearsal, serial position effect
and chunking
• 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.
– organisation of long-term memory including declarative and
episodic memory, and semantic network theory
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 Memory of specific events or
personal experiences
The events of a party
you attended on the
weekend.
-Semantic Info/facts we have about the
world.
Knowing there are 12
months in a year.
– organisation of long-term memory including declarative and
episodic memory, and semantic network theory
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.
Alan Baddeley and Graham Hitch’s model of working memory:
central executive, phonological loop, visuo-spatial sketchpad,
episodic buffer
•
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).
levels of processing as informed by Fergus Craik and Robert
Lockhart
•
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.
manipulation and improvement of memory:
– forgetting curve as informed by the work of Hermann
Ebbinghaus
Ebbinghaus’s forgetting
curve suggested that
forgetting occurs rapidly
after learning and then
slowly declines over
time.
50 % of memory loss occurs
within the first hour after
learning.
The Forgetting Curve
shows the rate and
amount of forgetting
over time.