Psych Chap 5 - The Psychobiological Process of Memory

3 core processes of memory

Encoding, storage and retrieval

Encoding

Conversion of sensory information into a usable form so that it can be neurologically represented and stored in memory

Storage

Retention of the encoded information over time

Retrieval

Recovery of stored information for use in conscious awareness

Atkinson-Shiffrin multi-store model

('The Atkinson-Shiffrin model' or the 'multi-store model')

Represents memory as consisting of three separate stores (components) called sensory, short-term and long-term memory. Each store processes information differently and varies in function, duration and capacity, and they operate simultaneously and interact.

Atkinson-Shiffrin Model Diagram

The information-processing approach

The Atkinson-Shiffrin model is sometimes referred to as an information processing model, because it describes memory as a system with inputs and outputs, similar to a computer.

Sensory Memory

Storage of incoming raw sensory information for a very brief period after the stimulus has ceased.

How is sensory memory involved in seeing images smoothly?

Sensory memory stores iconic (and echoic) sensory impressions long enough for each to slightly overlap the next, meaning that we perceive the world around us as continuous, rather than as a series of disconnected stimuli.

What are the two sensory registers?

Iconic memory and echoic memory

Iconic memory

A brief sensory memory for incoming visual information

Echoic memory

A brief sensory memory for incoming auditory information

Duration of sensory memory

Varies depending on the sensory register/ sense:

- Iconic lasts 0.2-0.4 seconds (briefer to perceive smooth images)

- Echoic lasts 3-4 seconds (to allows us to process speech better, as we understand words fully, not based on each sound, so need to be able to remember all the sounds to string them together)

Capacity of sensory memory

Virtually unlimited. Sensory memory takes in all sensory stimuli present, but only the ones attended to are transferred to short term memory.

Evidence for sensory memory (duration)

Sperling's (1960) established the duration of iconic memory by momentarily showing participants a grid of 12 letters, then immediately asking them to recall a particular line. They could, if asked quickly enough, as it was stored in their heads for a third of a second.

Short-term memory

The store where information can be consciously perceived and processed. It’s the thoughts and experiences we are having right now, mostly of the form of sounds and images, and it’s where all learning, feeling, thinking, and other mental processes take place.

2 sources of information entering the STM

1. Information from sensory memory to which we pay attention

2. Information from long-term memory that has been retrieved

Duration of STM

Approximately 18-30 seconds, unrehearsed. Information begins to decay within seconds and by 18-20 most is gone.

Maintenance rehearsal

Repeating information over and over in our heads to keep it active in short-term memory for a longer duration.

Capacity of STM

7 +/- 2 items

Evidence for STM (duration)

Peterson and Peterson (1959) showed participants a trigram (e.g. CQN), then got them to perform a distractor task so they couldn't rehearse the trigram in their heads until a light flashed. The later the light, the worse recall

Evidence for STM (capacity)

George Miller (1956) measured digit span - the average number of digits that participants can repeat back in the right order, without making errors.

Chunking

The grouping of separate bits of information into larger units of information to increase the capacity of STM

2 primary ways info is lost from the STM

Decay - Not being used

Displacement - Being pushed out

Working memory

Another term for short-term memory, emphasising its processing function. We can manipulate information in our heads (e.g. turn a mental object, add numbers).

The working memory model

Baddeley and Hitch (1974).

Central executive: controls processing and makes decisions

Visuospatial sketchpad: allows us to store and manipulate visual images

Phonological loop: allows us to 'hear' words and other sounds.

Working memory model image

Long-term memory

A relatively permanent store for information that is not currently being used, but can be recalled at a later time.

Duration of LTM

Relatively permanent. Highly relevant or accessed information can be remembered for a lifetime

Semantic networks

Organisation of information in meaningful networks in LTM.

Elaborative rehearsal

Connecting new information in a meaningful way to previously stored memories, in order to enhance its retrieval. Ensures information is well-organised and connected, making it easier to access if needed.

Capacity of LTM

Unlimited, as memories are stored in the creation of new synapses, not new neurons. Highly educated people have bushier dendrites than others due to more synaptic connections

Evidence for LTM and STM being separate systems

Serial Position Effect, the observation that items at the beginning and end of a list are recalled more accurately than those in the middle. Includes primacy and recency effect

Primacy Effect

Superior recall for items at the beginning of a list due to the extra capacity to rehearse the items at the beginning before there are too many to attend to. Evidence for LTM.

Recency Effect

Superior recall for items at the end of a list due to the items still being in your short term memory. Evidence for STM.

Two types of LTM

Explicit (declarative) memory and implicit (non-declarative) memory

Explicit memory

LTM with awareness that can be intentionally/consciously recalled and stated/described. Involves general knowledge and info about personal experiences retrieved at will. Two sub-types are episodic and semantic memory.

Episodic memory

Explicit LTM of personally experienced events associated with a particular time and place. Always include the self as the initiator or recipient of some action. Often involve a what, when and where.

Semantic memory

Explicit LTM of facts and knowledge about the world. Not tied with details of time and place like episodic memories, i.e. you can know the fact but not where you learnt them

Autobiographical memory

Memory for events that occurred in your life consisting of episodic memories (i.e., personal experiences at a particular time and place), semantic memory (i.e., factual knowledge), or a mix of the two. E.g. an autobiographical memory of school might combine seeing your teacher, and the fact that their name is Mrs Coonan!

Implicit memory

LTM without awareness that is retrieved automatically and cannot be articulated with words. Includes motor skills and more abstract concepts like what words, shapes and objects are without memory of learning them or awareness of them in our memory. Two types are procedural memory and classically conditioned responses.

Procedural memory

Implicit LTM for the skills involved in particular tasks. Includes motor skills and cognitive skills like reading, or liking a post. Require little/no intention to retrieve.

Classically conditioned memory

Implicit memories of automatic associations (classically conditioned responses) you’ve acquired. They are automatically retrieved from your LTM into your STM when CS is presented without any effort due to past association. Includes certain classically conditioned reflexes and emotional responses.

General connections between brain areas and implicit/explicit memory

Explicit: Hippocampus interacts with amygdala for encoding and consolidation, especially emotionally significant memories, and connects with neocortex for storage and retrieval.

Implicit: Cerebellum interacts with basal ganglia and motor programming areas of the neocortex to encode, store and retrieve implicit memories including those involved with habit formation, fine motor movement and simple reflexes.

Hippocampus location

Just above each ear in the medial temporal lobe area, just under the cerebral cortex are each hippocampi.

What systems is the hippocampus a part of?

Nervous and limbic

Hippocampus function

- Involved in the formation and encoding of new explicit memories, transferring them from STM to LTM.

- involved in the consolidation of explicit memories to ensure they are neurologically stable, long-lasting and organised.

- Plays a role in the storage and retrieval of spatial information.

- Connects with amygdala for emotional memories

- Connects with neocortex for storage and retrieval of explicit LTM

Consolidation

Neurobiological process of making a newly formed memory stable and enduring following a learning experience. Time is required after learning takes place for consolidation to occur.

Two phases of consolidation

1. Initial rapid process for temporary storage

2. Slower, more permanent process for long-term storage

Reconsolidation

When memories are retrieved, it is open to further consolidation and has to be 're-stabilised' by revising the memory with the new added information.

Does the hippocampus permanently store memories itself?

No, after temporary storage and consolidation, it instead transfers them to the neocortex for long-term storage, most likely in the areas that initially processed the information.

How is a memory retrieved as a single unit?

The hippocampus, through interaction with the cortex and other medial temporal lobe areas, integrates new incoming info with existing info to form networks of memories, establishing links between the different interrelated bits of a memory so they are organised and can be efficiently retrieved.

How is the hippocampus involved in emotional memories?

Through its interaction with the amygdala, the hippocampus enables the encoding of explicit long-term memories involving emotional responses

Spatial memory

An explicit memory for the physical location of objects in space. Enables us to navigate and learn to remember locations.

How is the hippocampus involved in spatial memory?

It is involved in the retrieval of spatial memories.

Amnesia

Loss of memory due to damage to neural structures

Anterograde amnesia

The inability to transfer new information from the short-term store into the long-term store. Caused by bilateral hippocampi damage, and affects explicit memories. Procedural memories unchanged, but person can't remember how they got the skill.

Retrograde amnesia

Inability to retrieve memories from before the point of brain trauma

Amygdala function

Processes and regulates emotions, particularly fear and anger. Involved in indicating emotional significance of memories to the hippocampus to aid in the the formation, consolidation, encoding and retrieval of memories that evoke an emotional reaction (mainly explicit), and learning involving emotion (classically conditioned emotional responses)

Medial temporal lobe

A region within the cerebral cortex comprised of a system of anatomically related structures, including the hippocampal region (hippocampus and amygdala)

Evidence for amygdala's role in classically conditioned fear responses.

Rats conditioned to fear a blue light as they expect an electric shock. Part of the amygdala is removed or damage, interfering with the acquisition and expression of the conditioned fear response, resulting in the rats no longer fearing the light.

Why do classically conditioned emotional responses involve long-term implicit memory? (think behaviourism)

Because they occur involuntarily due to an environmental stimulus, there is no conscious recall and the memory can be observed through the specific reactions associated with the conditioned response.

How does emotion influence memory encoding?

Level of emotional arousal at the time of encoding influences the strength of the LTM formed. Partly attributable to increased noradrenaline in the amygdala, leading it to attach more emotional significance to the experience and signal the hippocampus to encode more strongly.

Flashbulb memory

A vivid, highly-detailed and long-lasting memory that is very emotional. Demonstrates the amygdala's role in formation and storage of some long-term explicit memories.

Neocortex

Largest, most recently evolved and outermost layer of the cerebral cortex. (makes up 90% of cerebral cortex).

Connected to virtually all parts of the brain. Interacts with the hippocampus in the formation, consolidation, storage and retrieval of long-term explicit memories, and stores well-learned motor sequences and complex classically conditioned responses

Are explicit long-term memories always dependent on the hippocampus, amygdala and other medial temporal lobe structures?

No, as time passes after learning and consolidation has occurred, explicit LT memories stored in the neocortex gradually become independent of medial temporal lobe structures, meaning the neocortex has a vital role in the retrieval process.

How are long-term explicit episodic and semantic memories stored?

Widely distributed throughout the neocortex in areas, usually where the relevant information was first processed. When a memory is recalled, this network fires together, strengthening their connections as they become tied together as a single memory.

Where are episodic and semantic memories stored in the cortex specifically?

Semantic in both of the front and temporal lobes.

Episodic in the right frontal and temporal lobes.

Basal ganglia

Made up of subcortical structures connected to neocortex involved in generating and regulating voluntary movements, with memory roles including the formation and encoding of procedural habits with cerebellum and the encoding and storage of classically conditioned memories.

Basal ganglia and Parkinson's disease

Substantia nigra is part of basal ganglia, and therefore damage to this area specifically (but also other parts of basal ganglia) can lead to impaired voluntary movements that are commonly present in Parkinson's disease.

Evidence for basal ganglia's role in sensori-motor skill memory

Mirror tracing task cannot be learnt if damage to basal ganglia has occurred as ability to form implicit motor memories has been impaired. Damage to medial temporal lobe structures does not impact ability to learn to perfect the task.

Huntington's disease

Hereditary disorder characterised by involuntary bodily movements due to the degeneration of neurons in the basal ganglia

Habituation

Habitual learning; the process of growing accustomed to a situation or stimulus, leading to decreased responsiveness following repeated exposure to it. (E.g. getting less startled by a loud noise every time it occurs). Occurs unconsciously and memories based on this form of learning are implicit.

How is habituation a type of 'non-associative' learning?

Because it doesn't involve the association of two stimuli to produce a behaviour change.

Cerebellum

Structure at the base of the brain with multiple roles:

• Controlling fine motor movements, balance, posture and skilled sequences of movements (e.g. touch-typing and playing the piano), as well as ensuring smooth everyday voluntary movements.

• Involved in encoding, retrieval and temporary storage (well-learned stored in neocortex) of procedural memory involving motor skills, and further permanent storage of simple classically conditioned motor reflexes

• Spatial function with hippocampus

Evidence that the cerebellum forms and stores implicit classically-conditioned motor memories

Psychologist Richard Thompson conditioned rabbits to blink in response to a beep that they had associated with a puff of air. Destroying part of the cerebellum didn't remove the natural reflex to the puff of air, but did remove the learnt response of blinking due to the beep.

How does the cerebellum interact with the basal ganglia?

The cerebellum interacts with the basal ganglia and motor programming areas of the neocortex to encode, store and retrieve implicit long-term memories, such as those associated with habit formation, fine motor movements and simple reflexes.

Retrieval of autobiographical events

Events that have occurred in our own life are stored in episodic memory, and to retrieve it we must engage in 'mental time travel' to place ourselves in the context of the event, something unique to episodic memory. Semantic memory is not time-related (i.e. doesn't need mental time travel) but allows us to extract and integrate facts into autobiographical recall.

Imagined future

Episodic memory allows us to relive past experiences and use this information to construct a possible future scenario, such as playing out a scene in your head that hasn’t yet occurred, and integrating facts you know about current time (semantic memory).

Mental imagery

Perceptual representation not triggered directly by sensory input. Involved in retrieval of autobiographical events and constructing possible imagined futures.

Alzheimer's disease

Neurodegenerative disorder characterised by the gradual widespread degeneration of brain neurons, causing memory loss, a decline in cognitive and social skills, and personality changes. Age related but not a normal part of ageing.

Alzheimer's disease vs dementia

Alzheimer's is a specific brain disease that accounts for 70% of dementia cases and is a type and cause of dementia, which is a general term for symptoms like declining memory, reasoning or thinking skills.

Brain lesion

Any disruption of or damage to the brain's normal structure.

What type of memories are primarily affected by dementia?

Explicit episodic and semantic because hippocampas and medial temporal lobe areas are affected.

Progression of Alzheimer's brain damage

1. Hippocampal damage leading to anterograde amnesia

2. Degeneration spreads outwards to cortical areas and other medial temporal lobe areas, impairing LTM (especially explicit, while implicit are less affected)

3. Extensive brain atrophy (only visible post-mortem) and widespread brain lesions

Symptoms of Alzheimer's disease

Memory loss, confusion, unusual irritability, impaired decision-making

How is a diagnosis made for Alzheimer's disease?

No physical signs or one symptom can determine if someone has Alzheimer's. A working diagnosis is usually made on the basis of cognitive symptoms, and memory, general knowledge, intellectual and personal skills are assessed to determine that rate of deterioration. In autopsy, amyloid plaques and neurofibrillary tangles affirm diagnosis.

Examples of things that can be forgotten due to Alzheimer's disease

Events, words, names, ability to follow stories or directions, semantic facts and (a bit later) ability to perform daily tasks

Brain pathology of Alzheimer's disease

- Build up of amyloid plaques

- Neurofibrillary tangles

- Reduced acetylcholine

Amyloid Plaques

Build-up of neurotoxic protein in clumps around neurons that affect communication. In Alzheimer's, plaques mainly affect hippocampus and midbrain, leading to up to 3/4 of neurons being lost in these areas.

Neurofibrillary tangles

Twisted strands of highly soluble tau proteins found in the centre of dead and dying nerve cells

Acetylcholine

A neurotransmitter used by brain areas like the hippocampus and midbrain for memory and learning. Levels of ACh decrease with age but at an abnormal rate in those with Alzheimer's.

Alzheimer's disease and constructing imagined futures

Patients with known hippocampal damage have difficulties with mental imagery, including imagining novel/fictitious experiences, imagining plausible self-relevant future events, and remembering past experiences.

Is there overlap between episodic and semantic memory in imagining the future?

Episodic and semantic memories are supported by different neural systems and partially distinct brain areas, but there is overlap

Aphantasia

A type of neurodiversity involving an inability to form mental visual images of objects that are not present. Can be from birth or acquired.

Hyperphantasia

Overabundance of visual imagery, often occurs simultaneously with synaesthesia

What areas of the brain are disrupted in those with aphantasia?

The connection tends to be weaker between the visual cortex areas at the back of the brain and the cortex involved in attention and decision-making in the frontal lobes.

Mnemonic

(Mnemonic device) Technique or system used to aid memory involving using information already stored in LTM by forging a link between new information to be remembered and information already encoded, in order to organise information into a cohesive whole so that retrieval of part of the information leads to retrieval of the rest of it.

Is more or less information encoding when using a mnemonic?

More, but the additional information more richly encodes the material to make it easier to locate and retrieve because it has enhanced organisation in LTM

Written Cultures

(Western) cultures that share learning through written modes