U3 AOS2 - Memory

Memory

The process of encoding, storing, and retrieving information that has been previously encountered.

Encoding

The process of converting the raw information from external stimuli into a useable form which is stored in the brain for later use.

Storage

This converted information is then retained in the brain and accessed and used in the future.

Retrieval

Accessing information which has previously been stored in long-term memory and bringing it to conscious awareness in short-term memory.

Atkinson-Shiffrin Model

A model that consists of 3 separate stores that operate simultaneously and interact in different ways. Outlines three distinct memory stores (sensory, short-term and long-term), all of which have different functions, capacities (number of memory pieces) and duration (length of time).

Structural Features (Atkinson-Shiffrin)

3 different stores – Permanent, built in fixed features of memory that do not vary from one situation to the next.

Sensory Memory

A store of memory which very briefly stores raw information detected by the senses; the entry point for information in memory in which stimuli is retained for a very brief time in their original raw form.

Sensory Memory – Function

Retain information that has been detected by the senses in its raw form. Entry point for information. Receives new sensory information from the environment.

Sensory Memory – Capacity

Unlimited (potentially unlimited)

Sensory Memory – Duration

0.2 – 4 seconds

Two types of Sensory Memory

Iconic memory – Temporarily stores visual information for a brief amount of time (0.2-0.4 seconds); Echoic memory – Temporarily stores auditory information or sound which is detected in the environment (3-4 seconds)

Iconic Memory

Visual memory – sensory store of objects in your visual field. Duration: 0.2 - 0.4 seconds.

Why does Iconic Memory clear quickly?

If iconic memory did not clear quickly, multiple sensory memory representations of a scene would overlap and distort your perception of the world.

Echoic Memory

Sensory store of all sounds within our range of hearing. Duration: 3 - 4 seconds.

Echoic Memory – Role

Important role in speech and language comprehension, enables storage of all sounds that make a word so it can be processed as a whole and allows an entire sequence of words to be held (sentences) so meaning can be formed.

Short-Term Memory (STM)

A store of memory that temporarily stores a limited amount of information that is consciously being attended to and actively manipulated. Has a limited storage capacity and a limited duration – information is rapidly lost unless it is rehearsed.

STM – also known as

'Working memory' because you are aware of all the information that you hold in this memory store and are consciously manipulating ('working on') it.

Where does information in STM come from?

Information in STM can arise from both sensory or long-term memory. Information from sensory memory which you have paid attention to moves into STM. Information from LTM that you choose to recall can also exist within STM.

STM – Function

Temporarily stores a limited amount of information that is consciously being attended to and actively manipulated. SM that is attended to may pass to STM. Information from LTM that is retrieved can enter STM. Enables us to manipulate information entering from sensory memory or retrieved from LTM.

STM – Capacity

7 +/- 2 items (5 – 9 pieces of information)

STM – Duration

18 – 30 seconds

What can happen to information that reaches STM?

It can be: Discarded; Changed by further encoding; Retained in STM while being used.

Chunking

The grouping of separate bits of information into a larger single unit of information; used to improve STM capacity.

Maintenance Rehearsal – Definition

Involves repeating information so that it can be held in STM for an extended duration. Often meaningless and therefore does not easily transfer to LTM.

Maintenance Rehearsal – Advantages

Allows information to be stored in STM for longer than usual; Good method for remembering meaningless information.

Maintenance Rehearsal – Limitations

Does not add to understanding; Limited effectiveness in transferring from STM into LTM; Easily interrupted by information entering; Difficult to practise in situations where information entering STM is rapidly changing.

Elaborative Rehearsal – Definition

Based on rehearsing the meaning of information. It involves making useful links between new and old information that already exists in the LTM. This link helps associate and organise new information and improves encoding.

Elaborative Rehearsal – Advantages

Increases understanding; Adds more detail which increases retrieval chances; Makes information more accessible because it creates more potential retrieval cues; Increases possibility of long-term retention because it organises new information according to meaning.

Elaborative Rehearsal – Limitations

Relies on the ability to retrieve information already in the LTM; Takes longer than maintenance rehearsal; Requires more conscious effort than maintenance rehearsal.

Long-Term Memory (LTM)

A store of memory in which a potentially unlimited amount of information is stored for a relatively permanent amount of time. Contains all the information you retain from past events as well as your knowledge of facts.

LTM – Function

Stores information that can be retrieved for future use. Storehouse for information encoded from STM.

LTM – Capacity

Unlimited

LTM – Duration

Relatively permanent / Potentially Permanent

Is information stored in LTM in conscious awareness?

No – information stored in LTM is not in conscious awareness.

Serial Position Effect

A tendency for free recall to be superior for items at the end and beginning of a list compared to items in the middle. Items in the middle of a list are the most likely to be forgotten.

Primacy Effect

Enhanced recall of information presented at the beginning of a list due to this information being rehearsed and transferred into long-term memory. This information is the most likely to be rehearsed and therefore most likely to be transferred into LTM, where it is stored and available for retrieval.

Recency Effect

Enhanced recall of information presented at the end of a list due to this information remaining in short-term memory. This information is likely to still be in the STM store by the time it is retrieved, meaning it is still in conscious awareness. The recency effect is typically stronger than the primacy effect.

Loss of Memory from SM

Unattended information fails to transfer into short-term memory, it is thus lost at the first stage.

Loss of Memory from STM

If the information in your short-term memory is not processed and encoded in long-term memory, it can be pushed out by new incoming information (displacement) or fade away on its own after the duration of STM has expired (decay).

Displacement

When information in STM is pushed out by new incoming information.

Decay

When information in STM fades away on its own after the duration of STM has expired.

Loss of Memory from LTM

Forgetting occurs due to retrieval deficit and interference from similar memories.

Atkinson-Shiffrin Model – Strengths

The model distinguishes between the different stores involved in memory. It can explain how information is transferred to LTM from sensory memory and STM, and why forgetting occurs. This is demonstrated in the model's explanation of serial position effects.

Atkinson-Shiffrin Model – Limitations

It does not explain the different forms of long-term memory (e.g. events of our lives, how we organise knowledge of concepts and words, or how we learn skills). It fails to explain the neural basis of the different memory stores. The model ignores factors such as motivation and strategy. It does not account for individual differences in memory processes, storage duration, and capacity.

Retrieval and Elaborative Encoding

Deeper levels of encoding and retrieval practice strengthen long-term memories. Long-term retention requires information to be encoded meaningfully through elaborative rehearsal. Meaningful encoding involves a cycle of interaction between STM and LTM. Actively interpreting information in STM by relating it to information retrieved from LTM results in storage of your new understanding in LTM.

Retrieval-Practice Effect

Repeated effortful retrieval of information from LTM into STM strengthens the memory trace through a process of re-encoding. This 'retrieval–practice effect' has been reproduced by other researchers many times, making it highly reliable.

Retrieval Practice Study – Aim

To investigate whether rereading or retrieval practice is better at improving long-term retention.

Retrieval Practice Study – Method

Students from Washington University were randomly allocated to one of three groups. All participants were given a 250-word passage. Condition 1 (SSSS): Read the passage repeatedly in four 5-minute blocks (~14 times). Condition 2 (SSST): Read during three 5-minute blocks (~10 times) then took a single 5-minute recall test. Condition 3 (STTT): Read during one 5-minute block (~3.5 times) then spent three 5-minute blocks trying to recall as much as possible. Half were tested after 5 minutes, half returned a week later.

Retrieval Practice Study – Results

When tested after 5 minutes, recall was better for students who had read the text more often. When tested one week later, recall was much better for students who had tested their knowledge rather than rereading. Although repeated rereading can lead to good performance on an immediate test, most of the information will be forgotten within a week of learning.

Two types of Long-Term Memory

Explicit (declarative) memory and Implicit (non-declarative) memory. Explicit comprises semantic and episodic memory; implicit comprises procedural and classically conditioned memory.

Explicit Memory (Declarative Memory)

A type of long-term memory that is consciously retrieved. They are voluntarily retrieved from LTM and brought into conscious awareness. Also known as declarative memories which means they can be declared or stated to someone else.

Semantic Memory

A type of explicit memory that consists of general knowledge and facts about the world. Don't remember the circumstances in which the knowledge was acquired. Eg. Knowing that there are 7 continents or what 3x3 equals.

Episodic Memory

A type of explicit memory that consists of memories of personal experiences or autobiographical events. Involves knowledge of events that include events of our own lives. Eg. The memory of getting your driver's license, remembering details from when you went on holiday, and remembering what you ate for dinner last night.

Implicit Memory (Non-Declarative Memory)

A type of long-term memory that is unconsciously retrieved. The remembering usually occurs effortlessly. These memories are involuntarily retrieved.

Procedural Memory

A type of implicit memory that involves knowing how to carry out tasks, facilitated by motor skills. Includes learnt actions and motor skills that can be retrieved through performance rather than conscious recall. Eg. Knowing how to correctly kick a soccer ball or how to tie your shoelaces.

Classically Conditioned Memory

A type of implicit memory which involves an involuntary response to a stimulus which has repeatedly been associated with an emotionally arousing stimulus. Conditioned responses to conditioned stimuli acquired through classical conditioning, particularly those involving fear or anxiety. Eg. A person attacked by a large dog may become immediately overwhelmed when later seeing a similarly large dog.

Hippocampus – Location

In the medial temporal lobe, one in each hemisphere.

Hippocampus – Role in Memory

Primarily involved in encoding explicit memories; consolidates STM into LTM; encoding and consolidation of new explicit memories. Responsible for consolidation, which is a neurobiological process of making a newly formed memory stable and enduring following a learning experience. NOT involved in storage. NOT involved in forming or retrieving implicit procedural memories.

Hippocampus – Interactions

Interacts with the amygdala when encoding explicit long-term memories involving emotional responses. Interacts with the neocortex when storing and retrieving long-term memories associated with semantic and episodic memories.

Consolidation

A neurobiological process of making a newly formed memory stable and enduring following a learning experience.

Henry Molaison – Case Study

1953 – had surgery to relieve severe epileptic fits and the hippocampus was removed. Resulted in: partial or no memory of events 2-10 years prior to the operation; could not form new explicit memories; but he could retain new skills.

Henry Molaison – Explanation

The hippocampus is the memory formation area where different components of memory are integrated to form an episodic memory. Once the memory is formed the different components of memory will be gradually transferred to areas of the brain that specialise in LTM storage.

Amygdala – Location

Just above the hippocampus.

Amygdala – Role in Memory

Primarily involved in encoding the emotional component of classically conditioned and explicit memories. Key role in consolidation/formation of emotion-related memories, especially classically conditioned fear responses. Helps label the emotional components of memory such as fear.

Amygdala – How it works

When the amygdala detects an experience which is emotionally arousing, it signals to the hippocampus that it is meaningful, enhancing strengthening of that memory during encoding. Noradrenaline stimulates the amygdala to attach more emotional significance to the experience and signals the hippocampus to encode and ensure long-term storage of relevant emotional details.

Amygdala – If there was no amygdala

There would be no CC fear response, just an explicit memory of the experience.

Amygdala – Damage Effects

People with damage to this area are unable to experience the emotions associated with episodic memories and do not acquire conditioned fear responses.

Neocortex – Role in Memory

Stores explicit memories. Once episodic and semantic memories are converted into a usable form in the hippocampus, they are stored within the neocortex to be retrieved for later use. Long term explicit memories are stored in neural pathways in the neocortex.

Neocortex – Structure

Composed of many layers and has 4 sections (temporal, occipital, parietal and frontal lobes). Part of the cerebral cortex. Higher cognitive functioning occurs. The frontal and temporal lobes are the main lobes involved in the storage of semantic and episodic memories.

Neocortex – Four Lobes

Frontal – coordination of goal-directed behaviour and manages complex processes such as decision-making; Parietal – plays a role in processing sensory information, spatial awareness and decision-making; Occipital – visual function; Temporal lobe – where the hippocampus and amygdala is. Emotions, meaningful memories, language and process sensory information.

Basal Ganglia – Role in Memory

Involved in encoding and storing procedural memories and classically conditioned memories that are associated with unconscious habits, behaviours, or procedures. Encodes and stores procedural memories via its connection with the cerebellum.

Basal Ganglia – How it works

Works together with the motor cortex and prefrontal cortex in the neocortex to initiate practiced sequences of movements and inhibit unwanted movements. The result is a smooth sequence of movements stored as a procedural memory. Role in incremental learning – for trial-by-trial feedback rather than assessing information and seeing patterns.

Basal Ganglia – Parkinson's Disease

An area of the basal ganglia (substantia nigra) is damaged in Parkinson's disease. Damage causes movement disorders including slowed movement, tremor and rigid posture. People with Parkinson's disease had difficulty forming stimulus response associations.

Cerebellum – Location

Base of the brain.

Cerebellum – Role in Memory

Encode and stores implicit procedural memories, such as those associated with habit formation, fine motor movements and simple reflexes through interactions with the basal ganglia and motor cortex of the neocortex. The storage site for implicit procedural memories, due to the cerebellum being involved in the processes of motor control, coordination, and balance.

Why are procedural memories preserved in people with hippocampal damage?

The basal ganglia and cerebellum can operate independently of the hippocampus, which is why the abilities to encode, store and retrieve procedural memories and conditioned associations are preserved in people with hippocampal damage.

Autobiographical Events

Memories of personally experienced events. Retrieval involves activation of both the hippocampus and frontal/temporal lobes, suggesting autobiographical events involve an overlap of episodic and semantic memory.

Semantic component of Autobiographical Events

Autobiographical events contain information that is semantic, such as the date or location of the event.

Episodic component of Autobiographical Events

Autobiographical events contain episodic components, which are more specifically related to the personal experience of the event, such as recalling the feeling of being nervous or happy during the event.

Possible Imagined Futures

Hypothetical experiences and situations that an individual has the ability to create and conceptualise in their mind. Eg. imagining what you're going to do tomorrow; imagining yourself in an argument with your parents and considering how it might go.

Role of Semantic Memory in Constructing Possible Imagined Futures

Semantic memory is involved as individuals must be able to envision possible scenarios that are consistent and fit in with what they already know about the world.

Role of Episodic Memory in Constructing Possible Imagined Futures

Allows individuals to construct a possible imagined future that is subjective and includes more richly detailed elements, such as the people involved or emotional reactions.

Effect of Hippocampal Damage on Imagined Futures

Patients who sustained damage to their hippocampus not only experienced difficulty remembering past events, but also struggled to imagine future scenarios. The ability to imagine futures is very important as mentally 'trying out' different scenarios can guide our future behaviours.

HSAM (Highly Superior Autobiographical Memory)

People can recall very detailed information about personal experiences such as where they were when Prince Harry and Meaghan got married. They usually perform similar to others in normal memory tests.

SDAM (Severely Deficient Autobiographical Memory)

People report an inability to vividly remember personally experienced events. They only have autobiographical memories of their lives reported from a third person perspective and find it difficult to imagine themselves in the future.

Neurodegenerative Disease

Disorders characterised by the progressive decline in the structure, activity and function of brain tissue. The neurons within the brain tissue gradually become damaged or deteriorate and lose their function.

Alzheimer's Disease

A neurodegenerative disease characterised by the gradual widespread degeneration of brain neurons, progressively causing memory decline and deterioration of cognitive and social skills and personality changes. Age related, but not a normal part of the ageing process. The outer part of the brain is usually the area affected first, especially the hippocampus.

Alzheimer's – Early Symptoms

Impairment in forming new memories; impaired recent episodic memories; impaired memory for names; impaired decision making and confusion.

Alzheimer's – Progressive Symptoms

Frequent repetition of stories or questions; failure to recognise family members.

Alzheimer's – Memory Loss Involves

Events (may forget part or all of an event); words or names; written and verbal directions; stories on TV, in movies or books; stored knowledge (historical or political information); everyday skills (dressing and cooking). Also: severe personality changes; difficulty imagining new experiences.

Alzheimer's – Brain Damage

Only found through post-mortems. Hippocampus is the most affected. Reduced levels of acetylcholine. Amount of folds in the cortex decreases. Fluid-filled spaces (ventricles) are enlarged. Overall declarative memory is impaired. Episodic memory is affected first, and then semantic memories. Brain shows cortical and sub-cortical areas that look shrivelled and shrunken; loss of volume in hippocampus.

Acetylcholine in Alzheimer's Disease

Activates muscles, helps with arousal and is linked with STM and learning. Decreases naturally as we age but decreases faster than usual with Alzheimer's. Build up of amyloid plaque may contribute to this by destroying Ach-transmitting neurons.

Amyloid Plaques

Fragments of the protein beta-amyloid that accumulate around neurons into insoluble plaques that inhibit communication between neurons. Sticky, abnormal clusters of protein fragments; attach themselves outside and around neurons, impairs the synapses and interferes with communication between neurons.

Neurofibrillary Tangles

An accumulation of the protein tau that forms insoluble tangles within neurons, which then inhibit the transportation of essential substances and eventually kill the neuron entirely. A build up of protein inside the neurons; these damaged neurons inhibit transport of essential substances through the neuron and lead to neuronal death.

Amyloid Plaques vs Neurofibrillary Tangles – Normal Ageing

Even though both amyloid plaque and neurofibrillary tangles can occur as part of the normal ageing process, they are much more abundant in those with Alzheimer's disease.

Progression of Alzheimer's Disease

Hippocampus damaged first – disrupting encoding and retrieval of semantic and episodic memories. Then neocortex affected – stored memories are lost and cognitive deficits occur. In final stages, cerebellum is affected – decline in cognitive performance, and a decline in accuracy, speed and consistency of information processing.

Alzheimer's – Effect on Autobiographical Memory and Imagined Futures

Patients may struggle to retrieve semantic and episodic components of personally experienced events. May also struggle to encode memories about recent events. People with Alzheimer's disease find it difficult to imagine themselves in future situations due to damage to the hippocampus affecting the capacity to draw on episodic and semantic memories needed to plan and construct new future scenarios.

Alzheimer's – Diagnosis

Currently no single diagnostic test for Alzheimer's disease. An entirely accurate diagnosis can only be made after death when an autopsy involving microscopic examination of brain tissue is conducted.

Alzheimer's – Cure

There is no cure for Alzheimer's disease but medications that increase acetylcholine can slow symptoms.

Mental Imagery

The perception-like experience in our conscious thought in the absence of external sensory stimuli. E.g. when we 'see something in our mind's eye' or hear a song in our heads. There are individual differences in the way people experience mental imagery.