Memory (L5) Flashcards
What is memory?
The process that allows us to record (encode), store, and later retrieve experiences and information.
Brain as computer? How are they similar:
The recording (encoding) system is similar to that of an input device.
The memory unit within a computer works the storage and retrieval aspect of the brain.
Three stages of memory
- Encoding
- Consolidation (long-term storage)
- Retrieval
Three main types of memory
- Sensory memory: immediate storage for information from senses
- Short-term or working memory: active temporary storage for ongoing task performance.
- Long-term memory: persistent storage lasting up to a lifetime.
Stages of (human) memory - theory
- Atkinson and Shiffrin (1968) proposed this three stage/component model of (human) memory:
Sensory input leads into sensory memory. Encoding/attention leads from sensory memory into working (short-term) memory (rehearsal also loops back into working memory). Encoding leads from working memory to long term memory, and retrieval leads from long term memory to working memory. This encoding/retrieval stage is part of storage/consolidation.
(THE PICTURE ON THE SLIDE WORKS BETTER TO UNDERSTAND THIS THEORY).
Sensory memory (+ two types of storage)
Briefly holds incoming sensory information
- There is the iconic storage (<1 sec): visual information.
- There is the echoic storage (several seconds): auditory information.
Short term memory
Short term (STM) or working memory holds a limited amount of information temporarily.
- It is critical for ongoing processing of events
- Lasts for 12-30 seconds but can be prolonged by rehearsal.
- Capacity is limited (7, give or take 2, meaningful items), however items can be chunked (e.g., phone numbers).
- This is the encoding/attention to working memory section of Atkinson’s theory.
Working memory model (+ 4 main aspects)
Alan Baddeley proposed that short term memory is an active process.
Four aspects of the model:
- Phonological loop
- Visuospatial sketchpad
- Episodic buffer
- Central executive
Phonological loop (working memory model) (4)
- Stores mental representations of sounds
- It maintains info via rehearsal.
- Explains why long words are harder to memorise than short words.
- A loop in seconds rather than items.
Visuospatial sketchpad (working memory model)
Stores visual and spatial information.
Episodic buffer (working memory model)
- Integrates and manipulates information from the phonological and visuospatial sketchpad.
- Words are chunked into meaningful phrases.
Central executive (working memory model)
- Directs overall action, controls the focus of attention, and integrates information in the episodic buffer.
- Is at the head of each other section.
Long term memory (2)
- LTM can persist for much longer periods, often for life.
- LTM must consolidate to persist for this long (this is the storage/consolidate aspect of Atkinson’s theory).
Primacy and recency effects
- Information in the STM decays rapidly unless it is rehearsed.
- Rehearsal is likely important for STM to become consolidated into LTM.
- The distinction between STM and LTM can be observed in primacy and recency effects.
- PRIMACY reflect LTM while RECENCY reflects STM.
- The recency effect can be eliminated by introducing a delay before asking the participant to recall the items.
Long term memory types (2)
- Declarative memory (factual information)
- Semantic memory (general knowledge) e.g., Paris is the capital of France.
- Episodic memory (personal episode) e.g., We ate tacos yesterday.
- Procedural memory (skills and habits) e.g., tying a knot, riding a bike.
Memory formation & types of encoding
Levels of processing: deeper processing leads to better retrieval.
- Structural encoding
- Phonological encoding
- Semantic encoding
Structural encoding
- Shallow
- General features of a stimulus
POTATO: is the word in capital letters?
Phonological encoding
- Deeper
- Specific (linguistic) features of an object
HORSE: does this word rhyme with ‘course’?
Semantic encoding
- Deepest
- Remembering what the stimulus means
TABLE: does this word fit in the sentence “the man peeled the ____”?
Types of rehearsal (2)
- Maintenance rehearsal
- Elaborative rehearsal
Maintenance rehearsal
- Rote memorisation of information
- Uses structural or phonological encoding
Elaborative rehearsal
- Professional actors do not simply memorise their lines, but typically first imagine themselves being the person whose role they are playing.
- This allows them to attach meaning to the lines and behaviours.
- Uses semantic encoding.
Associative network
- Each concept is represented by a node
- Lines represent associations between concepts.
- Shorter lines indicate stronger associations.
- Activation of one node/network leads to spreading activation of related concepts.
- Neighbouring nodes are likely controlled by topdown modulation.
- This guides how we actively sample our environments by integrating information from STM and LTM
- Consistently being updated in response to internal cognition and new experiences.
Semantic memory
Can be represented as similar concepts
Red + Truck –> fire truck
Episodic memory
Can be represented as a sequence of events
Key in ignition –> start car –> drive to AH –> buy food.
What can associative networks lead to? (3)
- Misinformation effect
- Source confusion
- False testimony or confessions
Misinformation effect
Post-event experiences altering episodic memory.
Source confusion
Recognising something without knowing where we encountered it.
False testimony or confessions
People can be convinced something is true based upon altered memory for it.
Retrieval cue
A stimulus, whether internal or external, that activates information stored in long-term memory.
How does associative network work?
Activation begins with a (set of) internal or external cue(s), and cascades through the network. The more cues the stronger the activation of associated nodes.
Memory retrieval (general). What is it enhanced by? What areas of the brain are important?
- Retrieval is enhanced by a similar context to that where encoding occurred.
- Retrieval is also enhanced by a similar state or mood to that where encoding occurred.
- Memories of events or concepts that are more arousing, emotional, stressful, are better recalled.
- Adaptive value
- Pontine brainstem regions and amygdala are important for this.
Why do we forget? (4)
- Encoding failure
- Decay
- Motivated
- Inference
Encoding failure (forgetting)
Much of what we sense simply is not processed deeply enough to commit to memory.
Decay (forgetting)
One theory proposes that physical memory traces reduce with time (e.g., associative links).
Motivated (forgetting)
Conscious or unconscious repression of memories.
Inference (forgetting) + types
- New memories can obscure/alter older ones.
- Proactive: previous memories interfere with encoding/consolidation of new ones.
- Retroactive: new memories interfere with retrieval of older ones.
Memory disorders (3)
- Amnesia
- Post traumatic stress disorder
- Dementia
What is amnesia and what is it caused by (4)?
Amnesia refers to a loss of, or inability to form, long-term memories.
Amnesia can be caused by:
- Trauma (blunt force)
- Disease (stroke, tumours)
- Surgery (for epilepsy)
- Dementia, etc.
What are the types of amnesia (2)?
Retrograde amnesia
- Previously consolidated memories can no longer be retrieved.
Anterograde amnesia
- New memories cannot be formed or consolidated.
What is post traumatic stress disorder?
PTSD is persistent, recurrent memory for traumatic events, leading to chronic stress and anxiety.
Memory consolidation is a cyclical process - meaning it is repeatedly being encoded and retrieved. This process can be amplify the emotional response, and as a result these memories are difficult to suppress.
What can PTSD be treated by? (3)
- Drugs that reduce anxiety (anxiolytics).
- Behavioural-cognitive therapy: recalling traumatic events and gradually reducing the experience emotional response with the guidance of a therapist.
- A combination of these.
What is dementia and what aspects of the brain are effected?
Dementia is the (usually age related) progressive decline in cognitive ability.
- Particularly in the Alzheimer’s type dementia, this decline often begins with a loss in the ability to retrieve LTM.
- Alzheimers pathology starts in the pontine brainstem, proceeds to hippocampus, and gradually to the rest of cortex.
Important brain regions for the formation of memory (6)
- Prefrontal cortex
- Frontal cortex
- Thalamus
- Cerebellum
- Hippocampus
- Amygdala
Brain regions for sensory and working memory
- Processed in the sensory areas of the cerebral cortex.
- Activates a network of cortical areas located across different lobes of the brain.
- Prefrontal cortex plays a key role.
Important brain regions for long term memory
- Hippocampus and surrounding areas are critical for consolidation of declarative LTM (semantic, episodic).
Patient HM
Hippocampus removed bilaterally that resulted in complete anterograde amnesia but little to no retrograde amnesia.
He also had intact procedural memory.
Long term plasticity
The neuronal basis of memory formation is likely through a mechanism called long-term plasticity.
This lasting change in the sensitivity of a neuron to inputs that cause it to fire action potentials.
- Long term potentiation
- Long term depression
- Established by Eric Kandel. Existing axons form new synapses with the postsynpatic cell. New axons are also produced by the presynaptic cell.
Long term potentiation
Increased sensitivity (responds more readily to the input).
- Long term potentiation can be produced by strongly stimulating the presynaptic neuron and recoding action potentials from the postsynaptic one before and after this stimulation.
- The amplitude of the excitatory postsynaptic potential (EPSP) is increased following the stimulation.
Long term depression
Decreased sensitivity (requires more input to fire).
