MODULE 3
Module 3 — Short-Term Working Memory 🧠
Learning Outcomes:
Compare and contrast ‘place’ and ‘state’ models of working memory
Apply the Baddeley model to explain a working memory task
Deconstruct a working memory task using the component process model
Predict the effects of cortical lesions on working memory performance
Describe persistent activity as a neurophysiological mechanism of working memory
Critically analyze primary research articles and integrate how they add to our understanding of working memory
01: WORKING MEMORY AND ITS CAPACITY
What is short term memory?
The ability to keep new info in mind when not presented.
The process of producing long-term memories includes, sensory information being temporarily _____ in short-term storage. The info is then _____ into long-term storage.
encoded, consolidated
Explain working memory.
Manipulation of information retrieved from long-term storage or pulled directly from short-term storage.
Constantly active
The manipulation of incoming sensory info is an _____ process as it’s part of our ‘conscious’ experience.
explicit
What are the 3 characteristics for the parameters of working memory?
Time:
one of the principle limitations
duration of maintaining selective attention
info is held temporarily, unless transferred to long-term memory
Limited Capacity
Sustained Attention
How is working memory retained?
Cognitive process — attention and rehearsal
incoming sensory info is related to representation or concepts already stored in the long-term memory
What is a major way of increasing capacity?
Chunking
What are the 3 stage process of the Change Detection Task
encode
delay — persistent activity in the brain regions like the prefrontal cortex
response
What are the 2 models to explain capacity limitations for visual working memory?
Slots and resource model
Explain slots model.
each item is held in an individual ‘slot’ in the working memory
accuracy of the memory is fixed for each item
Who studies memory capacity using the change detection task to explain slot models?
Luck and Vogel
Explain the continuous resource model.
working memory is a limited resource distributed evenly between all items in a scene
hazy memory of an object with or without a ‘slot’
02: PLACE AND STATE MODELS OF WORKING MEMORY
Explain the place metaphor.
That types of memory can be localized to specific brain regions.
Baddeley and Hitch model
Capacity would be at the rate which info is rehearsed or transferred from one store to another.
Explain the state metaphor.
Working memory is an active state that a sensory representation of LTM can be placed into. Allowing for conscious reflection and manipulation.
LTM would remain in place but change its ‘state’ to be accessed for working memory
What is the component process model
A state model
What were the results found in Baddeley and Hitch research on the Multicomponent Model?
Individuals can complete 1 verbal + 1 visuo-spatial tasks but have difficulty performing 2 verbal or 2 visuo-spatial tasks simultaneously.
tasks requiring phonological processing and visuo-spatial processing occur using 2 independent systems.
introduced the idea of the place metaphor
Selected processes and representations are distributed and communicated through reverberating signals
What are the components of the multicomponent model?
Central Executive —> overlooks and coordinates the other components. Allocating attention to different systems
Visuo-spacial Sketchpad —> encodes visual and spatial info.
Episodic Buffer —> temporary storage system for the interaction between different components. Also allos memories pulled from LTM and interact with these components (Visuo-spatial and phonological)
Phonological Loop —> spoken and written material
03: NEURAL PROCESSES: BRAIN REGIONS AND NEURAL MECHANISMS
Sensory representation
sensory receptor
early processing
thalamus
primary sensory cortex
association cortex
Function in working memory: PFC
‘central executive’ for focusing, attention, ordering, inhibiting
doesn’t store contents of working memory
Dorsolateral PFC —> spatial attention
Ventrolateral PFC
left —> control of phonological loop (rehearsal)
right —> visual spatial info (visuospatial sketchpad)
Function in working memory: Perietal Cortex
spacial working memory (where object is located)
not visual object working memory (what)
right side = processing spatial info
left side = processing verbal info
‘top-down’ control over sensory representations and motor actions activated in ore posterior brain regions
it is conected reciprocally to porterior sensory regions of the brain
Function in working memory: Temporal Cortex (verbal)
verbal working memory
Function in working memory: Temporal Cortex (visual)
visual working memory (what is being seen)
not where
Function in working memory: Hippocampus
no effect on working memory
long-term memory is impaired
ex: HM
Describe persistent activity (PA).
Continuous firing of neurons during a delay period in the absence of a sensory stimulus. It has an important role in short-term maintenance and working memory.
What are the 2 key conditions for PA to be determined as a mechanism of working memory?
PA must be stimulus-specific
PA must be able to predict working memory errors
How is PA observed in neurophysiology, EEG, fMRI.
Neurophysiology —> continued spiking activity in neurons during delay period
EEG —> increased signal in certain brain regions
fMRI —> increased blood flow to regions of the working memory network
Where is persistent activity taking place?
first observed in the PFC as well as sensory association areas like the parietal and temporal cortex
“PA was holding the representation in working memory”
fMRI suggested that the activity could be decode in the primary sensory areas like the primary visual cortex
Martinez-Trujillo used electrophysiological studies to say that PA wasn’t observed in the spiking activity of the primary sensory areas and only observed in the PFC and sensory-association areas.
How is PA generated and maintained?
It is not well understood but there are 2 possible hypotheses:
Neurophysiological Mechanisms
For intrinsic persistent firing
If the afterdepolarization is strong enough (ex: close enough to the AP threshold), then persistent spiking may occur.
Persistent firing = calcium-dependent due to chelation of Ca2+ ions
Neural Circuit Mechanism
Circuit dynamics within a network of neuronal populations
Cell assemblies can reverberate due to reciprocal connections —> can set up certain oscillatory frequencies
04: DEVELOPMENT AND ENHANCEMENT OF WORKING MEMORY
How is working memory different s a child and adult?
Child: linear increase with age and levels off after puberty
Adult: Stability between 20-50 and a linear decline from 55-80. This decline can be more pronounced when more complex tasks are being performed.
Lifetime = inverted U shape (peak at 30-40)
In simple tasks, older adults recruited more of the ________ this suggests a lower frontal cortex efficiency.
dorsolateral prefrontal cortex (DLPFC)
Older adults performed worse on tests that require both ____ and maintenance, compared to just maintenance. This is another reason that they lack their role in the frontal cortex.
manipulation
Can you train your working memory?
Yes! Specifically in letter-memory tasks
If you have good working memory, are you more intelligent?
Yes, done by one research with N-back tests and general intelligence showing a strong positive correlation.