the remembering brain - part 2 Flashcards
What is STM?
memory for info currently ‘in mind’ - limited capacity
What is LTM?
stored info that need don’t need to be presently accessed or consciously accessible
unlimited capacity
When is info in the LMT and when is it in the STM?
all info from minutes, hours, days ago in LTM
information which is presently brought to mind (cued) is moved from the LTM to the STM to be accessed. It is then (re)consolidated and stored
How does WM and STM differ?
STM - passive store used for maintenance
WM - info currently being manipulated, used for higher processes and various complex functions
What functions are supported by the WM?
active manipulation of info for high cognitive functions e.g reading
underlies execution of complex behaviour regardless of cognitive domains which are being engaged
What happens when WM fails?
the ability to carry out daily activities is impaired
How does working memory support complex activities e.g social situations?
Gathers sensory info from the environment
Retrieves schemas in LTM
This info stays active in WM and dictates how you behave
Outline Baddeley and Hitch’s WMM
Separate STM sores and executive system for manipulating and controlling info in stores
Slave systems - visuospatial sketchpad, episodic buffer, phonological loop, controlled by central executive
What is the episodic buffer?
Added later
Temporary store of info brought to mind from LTM when needed
Outline alternative arguments to the WMM
argue against separate STM stores
instead working memory is activity in LTM
Outline the structures of the phonological loop
Phonological store
Rehearsal mechanisms
Outline evidence for the existence of the phonological store.
Paulesu PET study
-STM memory for letters- store and rehearsal components
-and rhyming of letters- rehearsal system only
What are the neural correlates of the phonological loop? (Paulesu PET study)
Phonological loop = left supermarginal gyrus
Rehearsal system - Broca’s area (B44)
Outline Ranganath’s study into the visuospatial sketchpad.
Study by Ranganath et al., (2004) explored visual WM maintenance and long-term associative retrieval
Prescan – ppt shown either a face, a building, or a face and a building together
C1 – delayed matching to sample
* Aimed to test WM
* Ppt shown face or building , then 7s delay, then shown a face/building, had to say if it was a ‘match’ or ‘no match’ to the original face
C2 – delayed pairs associate
* Control aimed to test LTM
* Ppt shown a building, then 7s delay, then a face, had to say if it was a ‘match’ or ‘no match’ to the pair in the prescan
What were the results of Ranganath’s study into the visuospatial sketchpad?
Results for DMS trails
* Fusiform Face Area (face sensitive) activated on face trials
* Parahippocampal place area (place sensitive) activate on building trials
* Even in delay, activity in these areas remained above baseline activity = retain the knowledge/ maintaining single object in STM involves activating ventral stream representations
* Good performance on these tasks - frontal and parietal lobes activated during the delay period = these regions are functionally connected to frontal and parietal regions and involved in WM
What evidence is there for the connection between the WMM and the prefrontal cortex? How are these results interpreted?
Gazzinga
delayed response task in animal studies
animals had to retain location of unseen food during delayed period (working memory)
prefrontal lesions affect ability in performing this task
BUT - performance could be due to deficits in long term associative memory instead of WMM
How did Gazzinga test working memory vs associative memory for delayed responses on animals
To address - How do we know this is due to WM and not just very rapid associations being formed in the LTM about food and location?
A similar paradigm used to test associative memory
Food is paired with a visual cue (e.g a plus sign)
Measures ability to retain LT rules, and does not measure WM at all
During delay period, monkey doesn’t need to retain any visuospatial information (like WM) but merely the rule
PFC damage doesn’t impair ability to do this task – WM component (represented by PFC) is therefore separate
Outline an animal study which establishes PFC neurons contributing to maintaining information in WM
animal study:
- PFC neurons differential respond to different stages of the experiment (cue, delay, response)
- neurons active in delay provice neural correlate for keeping representation active after a triggering period is no longer active after response
- indicates neurons in PFC involved in keeping representation active in WMM/VSS during delay
when do PFC become active again to a response
remain active if animal needs to use info for forthcoming action
-if task conditions change, same neurones become responsive to new set of stimuli
what is the role of the PFC
activity represents the need to accomplish a specific goal rather than representing a specific item
what evidence is there for the goal-oriented role of the PFC?
Druzgal & Desposito
-PFC working memory for faces
-task to match faces
-PFC sustained activity across encoding delay and retrieval periods
-significantly more activity in PFC when more faces needed to remember
-indicates specific face is not represented, instead activity is for goal
how was the prefrontal cortex activity different to fusiform face area in Druzgal & Desposito’s study? what conclusions were drawn?
-FFA activity steep decrease during delay
-prefrontal cortex activity was consistent
-indicates FFA for specific representations of items
-prefrontal cortex for goal
The prefrontal cortex is important to sustain activity when we have to retain things in our mind without being specific to stimuli
What interaction does WM rely on?
interaction between PFC and other parts of the brain that contain perceptual and long term knowledge relevant to a goal
What does PFC activation represent?
-prefrontal cortex activation reflects representation of task goal
What is Petrides’ theory of WM?
assumes division of PFC into at least 2 separate processes
-maintenance and manipulation
Where does maintenance and manipulation occur in PFC?
ventrolateral PFC - retrieves info from LTM stores and maintains it in order to accomplish a task
doroslateral prefrontal cortex - uses info from VLPFC
manipulates and monitors info depending on task demands
(ev from self-ordered pointing task)
What areas of the PFC are involved in encoding?
-lateralised responses in PFC at encoding depend on the type of materials
-encoding of words or semantic materials involve left PFC
-encoding of spatial info or faces involve right PFC
How does the PFC have a role in LTM?
-role in memory encoding
-activation of PFC and hippocampus signals successful encoding of information
How does the PFC have a role in retrieval?
PFC regions aid in organisation, selection, monitoring and evaluation of processing what occurs at retrieval
what evidence is there for the role of PFC in retrieval?
-during free recall
-increased activity in DLPFC with increased demands
-as more need for monitoring in retrieval
what sort of retrieval causes most activity in dorsalateral PFC?
-free recall as info requires more manipulation and monitoring as there are minimal cues
-eg more than recognition
-PFC damage results in more impaired free recall than recognition memory
what is source monitoring?
related to recall and recollection that stresses the ability to attribute retrieved memories to their original context
how is the PFC involved in source monitoring?
-involved as placing event in context requires active evaluation process before we are able to access the origin of memory
how does damage in the PFC effect source monitoring?
-impairs putting memories in spatial and temporal context
-can recognise memories but fail to retrieve from correct source
-more likely to confabulate (report fabricated events)
summary of roles of PFC in memory
-maintaining info in working memory
-selecting info in environment to focus on (important for encoding)
-providing cues and strategies to enable memory retrieval
-evaluating content of memories eg source monitoring
