9 the remembering brain Flashcards
STM
memory for information currently “in mind”; limited capacity
LTM
LTM = stored information that need not be presently accessed or even consciously accessible; has virtually unlimited capacity
Hold about facts or events
Minutes hours days years ago
Resembles hard drive - able to access if need
• All information from minutes, hours, days and years ago
is in LTM, unless it happens to be presently brought to
mind (in which case it enters STM)
what is working memory
Term WM proposed as it captures better the idea that the information currently in mind is manipulated
Working memory plays a wider role in cognition for example speech comprehension that can be accomplished only by manipulating the information
Stresses the control we exert over a shorter memory store to control and manipulate information
what does STM give the idea of
Whereas STM gives the impression of a static/passive store
(maintenance)
STM - a more passive retention of material
Stresses the memory store itself
why is WM important
we refer to WM to denote the active manipulation of information within a STM store in the service of high cognitive functions (e.g., comprehension, reading etc.)
- WM underlies the successful execution of complex behaviour, regardless of the cognitive domain or domains that are being engaged (D’Esposito and Postle, 2015)
- When working memory fails, so too does the ability to carry out many activities of daily living - every aspecxt of decision making and goal directed behaviour relies on working memory
baddeley model of working memory
Seperate STM stores - slave systems controlled by the central executive system which is responsible for manipulating and controlling information within the stores
visuospatial sketchpad
episodic buffer
phonological loop
central executivre
working memory
Working memory - responsibly for retaining an manipulating memory at the present time is shown in the model of working memory
central executive system
responsible for manipulating and controlling information within the stores
visiospatial sketchpad
Visuospatial sketchpad- stm store in which retain limited amount of information related to visuospatial details
phonological loop
Phonological loop - verbal information for limited time
episodic buffer
Later - episodic buffer - slave system to central exec - retains episodic information for limited amount of time comes form LTM episodic information already stored
Studied less systematically than other
model of working memory presents stm stores as
Separate STM stores and an executive system for manipulating &
controlling info within the stores
who argues against seperate stm and ltm stores
Other approaches argue against separate STM and LTM stores (e.g., Cowan, 2001; D’Esposito, 2007)
seperate ltm stores
visual semantic
episode ltm
language
phonological short term memory - location
the phonological store lies posteriorly
– parietal lobes
Information is passively retained in limited capacity short-term stores
Information is passively retained in limited capacity short-term stores
– phonological STM, visuospatial STM
– Capacity limit of phonological STM assessed by span tasks
(Digit span, operation span)
what is the role of the central executive
The central executive is responsible for refreshing information in the stores (rehearsal) and manipulating that information (e.g. using the list of numbers in STM to perform calculations)
– In the PFC; some suggest various division of the PFC for various working memory functions
the central executive relies on the functions of the prefrontal cortex
evidence for independence of the buffers
Verbal Task
1: Hold in mind a few words Verbal Task
2: repeat the-the-the
Reduced ability to perform Task 1
Capacity of phonological loop shared between these two task
Reduced ability
Two task share limited capacity of same buffer of phonological loop
evidence for independence of buffers
verbal task 1 - hold in mind a few words
visuospatial task 2 - retain position of moving stimulus
no effect in performing verbal task 1
Each STM store/buffer has its own capacity allocation and functions relatively independently from the other
Functional Imaging evidence for the dissociation between Verbal and Visuospatial STM
PET study
smith et al
Short-term retention of either letters (verbal STM) or
location of markers (visual STM)
Asked to remember locations or letters after a delayed period of 3 seconds
Then presented a location marker or a letter and asked whether location or letter had been in the original array
findings of smith et al
Distinct brain regions are active in the two WM tasks
- Verbal STM – Left hemisphere
- Visuospatial STM – Right hemisphere
where is verbal memory lateralised
Predominantly left lateralised - identified within inferior frontal cortex
where is spatial memory lateralised
Predominantly lateralised in the right hemisphere and included areas within the inferior frontal cortex the parietal cortex and occipital cortex
digit span test
Phonological STM
Numbers - retain and immediately report back after examiner finished reading
1 second per number
Demands increase as successfully
Stops when two sequential errors in both trials
Report numbers backwards
Increasing working memory demands
Working memory rehearses memory but manipulates by reordering
Happens in a number of seconds
operation span
Participants read and verify a simple math problem
• Then read a word after the operation (such as Truck).
• The participants recall the words
• Greater load with more intervening words and operations
Recall words
Keep track and rehearse words
Dual task procedure
Increase working memory load - mathematical questions
Target is successfully retaining verbal information
capacity of phonological STM
Miller (1956) suggests span is 7 +/- 2; he thought of these as meaningful “chunks”
what does chunking rely on
Chunking relies on LTM, and on LTM-STM interactions
what did cowan argue about chunking
limit is lower - around 4
span not strictly related to meaninfulness of chunks bc
Span length lower for polysyllabic words (skeleton,
binoculars etc.)
– Span length lower for phonologically similar words (map, cat, cap etc.)
what does capacity of phonological STM depend on
Limit depends on opportunity for rehearsal (e.g. articulatory suppression)
Rehearsal - important for phonological STM
Lower when speech production task
Disrupts ability to rehearse the verbal material
length of words has an efect on capacity of STM
Length of words has an effect on capacity of STM
Significant reduction in short term capacity for longer words vs shorter words
The span of verbal stm does not rely on the meaning of the word and chunks - if this was the case wed be able to store longer words at the same level as short words
Instead the capacity seems to rely on the phonological characteristics of the items themselves
Span length - lower for phonologically similar words
Capacity of STM - organised by phonological characteristics of items and not so much my meaningfulness
what does the phonological loop contain - 2 components
According to the Baddeley model the Phonological loop contains a
phonological store component (i.e., verbal STM) and a rehearsal mechanism
what is the evidence for seperation of verbal stm and rehersal mechanism
Paulesu et al. (1993) PET study while
participants performed tasks
engaging:
• a) Short-term memory for letters (both store and rehearsal components) - sequences of letters
• b) rhyming judgments of letter (rehearsal system only) - does letter rhyme
where is the phonological store
left supramarginal gyrus
posterior and parietal areas
where is the rehersal system
Rehearsal system à Brodmann’s area 44 (Broca's area).
prefrontal cortex
inferior frontal cortex
visuospatial short term memory - slot model
• Slot model: A small number of memory ‘slots’, each capable of storing a single visual object with fixed precision.