Remembering the Brain 2 Flashcards
Describe the relationship between Working memory and short-term memory.
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.)
Describe Short-Term Memory
- Memory for information currently “in mind”
- Has a limited capacity
- A more passive/static retention of material
Describe Working memory.
- WM underlies the successful execution of complex behaviour, regardless of the cognitive domain or domains that are being engaged.
- When working memory fails, so too does the ability to carry out many activities of daily living.
- Motivated by goal directed behaviour.
Describe Baddeley’s (2000) Model of Working Memory.
- Proposes separate STM stores and an executive system for manipulating & controlling info within the stores.
What is the Visuospatial Sketchpad?
- the STM store retaining limited amount of info about visuospatial details.
- is a slave system to the central executive
What is the Episodic Buffer?
- the STM store retains episodic info for a limited amount of time.
- the episodic info comes from already stored info.
- is a slave system to the central executive
It is a temporary store that integrates information from the other components and maintains a sense of time, so that events occur in a continuing sequence.
What is the Phonological Loop?
- the STM store retaining limited amount of verbal info
- is a slave system to the central executive
How can the capacity of phonological STM be assessed?
- Assessed by span tasks
- Digit span
- Operation span
Where do phonological stores lie in the brain
- The phonological store lies posteriorly
○ parietal lobes
What is the role of the Central executive in phonological short-term memory?
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).
- suggestions that it relies on the prefrontal cortex
What is the evidence for the independence of the buffers in Baddeley’s model of working memory?
Each STM store/buffer has its own capacity allocation and functions relatively independently from the other
Phonological Loop
Verbal Task 1: Hold in mind a few words
Verbal Task 2: repeat the-the-the
Reduced ability to perform Task 1.
Visuospatial Sketchpad
Task 1: Retaining the position of a moving stimulus
No effect in performing Verbal Task 1
Describe the functional Imaging evidence for the dissociation between Verbal and Visuospatial STM.
PET study by Smith et al (1996)
- Distinct brain regions are active in the two WM tasks
- Verbal STM – Left hemisphere
- Visuospatial STM – Right hemisphere
How does working memory aid the digit span task?
Working memory manipulates and rehearses the sequence.
Describe the Operation Span Task
- It predicts verbal ability of the participant
- Ps read and verify a simple math problem
- Then read a word after the operation (such as Truck).
- Ps recall the words
- Greater load with more intervening words and operations
What affects the long-term capacity for remembering words?
○ Span length lower for polysyllabic words.
○ Span length lower for phonologically similar words
○ Greatly hindered when rehearsal cannot be carried out.
Where is the phonological loop located in the brain?
- According to the Baddeley model the Phonological loop contains a phonological store component (i.e., verbal STM) and a rehearsal mechanism
- Phonological store → left supramarginal gyrus
- Rehearsal system → Brodmann’s area 44 (Broca’s area).
Describe the slot model
- Examines Visuospatial Short-Term Memory
- A small number of memory ‘slots’, each capable of storing a single visual object with fixed precision..
Describe the resource model.
- Examines Visuospatial Short-Term Memory
- No upper limit on the number of items stored; instead, the more items that are held in memory, the less precisely each can be recalled.
What is the evidence for the Slot Model?
Luck and Vogel (1997)
- used brief displays of arrays (coloured squares and oriented coloured lines)
- Retain information about ~4 colours or orientations in visual working memory at one time
- Retain both colour and orientation of four objects
- Visual short-term memory capacity understood in terms of integrated objects rather than individual features
What is the evidence for the resource model?
Bays, Catalao & Husain (2009)
- Ps exposed to arrays.
- Ps presented with another array which had a probe location. They had to say which colour that square was in the original array.
- Location and colour of item was tested here.
- The more items that are held in memory, the less precisely each could be recalled
What did Bays, Catalao & Husain (2009) conclude when explaining the resource model?
Visual working memory consists of a common resource distributed dynamically across the visual scene, with no need to invoke an upper limit on the number of objects represented
Describe the Study carried out by Ranganath et al., (2004) when exploring the neural correlates of visuospatial STM.
- Prescan photos of faces and houses were displayed in pairs (one of each)
- Ps had to decide if the cue matched the probe image that was showed after a delay.
- DMS = Delayed matching-to-sample
○ Probed visual spatial working memory - DPA = Delayed paired associate
○ Probed visual spatial associative recall/ long-term visual spatial associative memory
What were the results of the Study carried out by Ranganath et al., (2004) when exploring the neural correlates of visuospatial STM.
- Activity within category-selective regions of inferior temporal cortex reflected the type of information that was actively maintained during both the associative memory and working memory tasks.
- Maintaining single object in STM involves activating ventral stream representations
○ functionally connected to frontal and parietal regions during the delay period - The communication between frontal and parietal areas defined the success of working memory maintenance.
What do the FFA and the PPA represent in the brain?
- FFA: Faces
- PPA: places
Describe the Delayed response task to investigate WM, using in animals.
- Measures WM in monkey
- Animal must retain the location of the unseen food during the delay period (WM)
- Prefrontal lesions affect ability in performing task
○ Affect ability to retain food location information
What is the problem with the Delayed response task, using in animals.
- Do the animals fail this task because of a general deficit in forming associations or because of a deficit in working memory?
Describe the Delayed response task to investigate Associative Memory, using in animals.
- Food is paired with a visual cue (plus sign)
- The task measures the animal’s ability to retain long-term rules
- No need for the animal to retain visuospatial information during the delay period (as in the working memory task)
- PFC damage disrupts a but not b
○ It has a critical role in visual-spatial working memory
How do Prefrontal Cortex Neurones respond in the Delayed response task
- Prefrontal neurons differentially respond to different stages of the experiment (cue – delay – response)
- PFC neurons active during the delay period provide a neural correlate for keeping a representation active after a triggering stimulus is no longer active
- They remain active (retain information) only if they animal needs to use the information for a forthcoming action
- If the task conditions change, the same neurons become responsive to a new set of stimuli
What did Druzgal & D’Esposito (2003) find when investigating the role of PFC in working memory for faces?
- The BOLD response began to rise at the onset of the encoding period. This response was sustained in the delay period.
○ This response was sensitive to demands on WM - PFC is critical for WM, because it sustains a representation of the task goal. It works together with the inferior temporal cortex to sustain information that is relevant for achieving the goal across the delay period.
Describe the interaction between the PFC and posterior cortex in working memory.
- PFC activation reflects a representation of task goal
- WM relies on interaction between PFC and other parts of the brain that contain perceptual and long-term knowledge relevant to a goal
Describe Pertrides’ Theory of Working Memory.
- Assumes division of PFC into at least two separate processes – maintenance and manipulation
- Based on functional imaging and neuropsychological findings.
- PET study showed that short-term retention of spatial information = ventrolateral PFC, but retention + update new locations = dorsolateral PFC
What did Pertrides’ Theory of Working Memory state that the areas of the PFC are responsible for?
- Ventrolateral PFC - subserves the maintenance of info to find the correct representation in the posterioral brain region, maintain this activity.
- activity → dorsolateral PFC: responsible for manipulating this info and for monitoring the accuracy of this information in order to perform the action.
What is the strongest evidence for the separation of STM and LTM stores?
Strongest evidence: Neuropsychological (patients) and behavioural (primacy and recency effects)
- double dissociation between H.M. and K.F.
Describe the failures of H.M.’s memory
- Inability to make new memories (i.e., cannot transfer new information into LTM)
- But intact short-term memory
Describe the failures of K.F.’s memory
- KF (Shallice & Warrington, 1970) ]
- Left parieto-occipital damage
- Normal LTM, good long-term learning (word lists, paired associates)
- Small STM span (low digit span)
How does Cowan’s WM model (Cowan, 2001) differ to that of Baddeley’s?
- Cowan’s WM model (Cowan, 2001) is similar to Baddeley’s formulation but does not necessitate separate stores for STM
- Instead central executive is responsible for selecting and activating LTM representations to bring them into “Focus of Attention”
- Unitary model of WM/STM
What is the role of the PFC in LTM?
- Responsible for maintenance and active control of information represented in LTM systems
- PFC functions are also prevalent in purely LTM tasks (encoding and retrieval).
What is the role of the PFC in memory encoding?
Kelley et al., 1998
○ Lateralised responses in PFC at encoding depend on the type of materials
○ Encoding of words or semantic materials (e.g., objects that can be verbalised) involve the left PFC
○ Encoding of spatial information or faces (as in Kelley et al., 1998 study) involve the right PFC
What is the role of the PFC at retrieval?
- PFC regions aid in the organisation, selection, monitoring, and evaluation of processing that occurs at retrieval
- Evaluation of what has been retrieved from LTM = monitoring – in DLPFC
- PFC damage results in more severe impairment during free recall as compared to recognition
What is the role of the PFC and free recall?
- Free recall means that there are minimal cues at test to aid memory performance
- Greater strategic search, organisation, selection and evaluation of retrieved information takes place in free recall than in recognition or cued recall
○ All these functions are subserved by the prefrontal cortex.
What is the role of the PFC and source monitoring?
- Related to recall and recollection that stresses the ability to attribute retrieved memories to their original context
- The PFC is involved at placing an event in context as this requires active evaluation before we are able to access the origin of the memory.
What happens when someone has PFC damage?
- Difficulty putting memories in their spatial and temporal context
- Subjectively may experience “remembering” (e.g., they can perform a recognition task) but they fail to retrieve the correct source
- They are more likely to confabulate: report narratives that include false memories (fabricated events)
What is the role of the PFC in memory?
○ Maintaining information in working memory
○ Selecting information in the environment to focus on (important for encoding)
○ Providing cues and strategies to enable memory retrieval
○ Evaluating the content of memories (as in source monitoring)
