SPRING WM and PFC Flashcards
what is the emergent view of WM
sensory areas maintain info while PFC provides top down control signals - assoc with executive function sin WM (Store and manipulate info)
describe the PFC
assoc cortex of frontal lobe
1/3 neo cortex (not limbic)
WM found as first temporal integrative function of pfc
describe fuster 1995 PFC and WM
memories formed by facilitation of selective synaptic links - develop self organised framework from sensory and motor cortical areas
-hierachial order of memories
microelectrode study in monkes show that sensory stimuli in wm persistently activate areas near the sensory cortex
describe funahashi et al 1989
delayed response task examine spatial memory in PFC ‘memory fields’ of monkeys
neurons in principle sulcus PS and FEF contain location of visual cues during delay
always fire in accordance to specific item location or orientation of stimuli
dlPFC - mapping of visual space
what cerebral structures is the PFC closely connected to (emergent view)
function of PFC rely on connections to other cerebral areas ie
brain stem
thallamus
amygdala
limbic system - (basal ganglia, hypothallamus)
how does brain activation change dependent on the WM task
exec control = PFC active
active maintenance of info = posterior regions specific to visuospatial/phonological info
- two processess are subserved by cortical structures
link between PFC and temporal lobe
fuster - temp lobe active in delay
interotempotal activity in memory tasks reflect afferent nerve connections from PFC
temp region connects to inferior pre frontal visual WM
TEMP = bottom up signals from V1 (visual) and PFC top down reg
what additional areas are activated along with the PFC in WM tasks
hippocapal formation involved in the consolidation of memory - reentrant network enables PFC and hippocampal formation to operate with other cortical and subcortical structures as an integrated unit
posterior parietal regions transmitting visuospatial to dorsolateral PFC
what is a re entrant network of PFC
goldman-rakic and friedman 1991
widely distributed group of acive neurons that communicate with eachother to achieve integrated and synchronised firing
ie dlPFC connect to ACC, posterior cing, oPFC and direct/indirect connections to enorhinal and perihinal cortices
majority of connections are bidirectional
problems with studying humans in connection between WM and PFC
difficult to observe consistency - widespread and differing lesions/problems
difficult to pinpoint what causes observed similarities/differences due to lesion overlap
muller, machado and knight 2002 lesions and wm/PFC
small lesions in d/vmPFC seperately not impair spatial WM
BUT wider lesions in dvlPFC (across regions) impair maintenance and monitoring of both spatial and obect info - distributed localisation of functioning in lateral PFC during WM
wm not localised to one area - spectrum of maintenance and monitoring across PFC
monkey and human brian overlap in WM tasks
maccaque activity correspond to healthy human
- mid frontal gyrus and DL PFC
salmon 1993 PET for WM
PET for wm tasks
frontal lobe mostly visual info
parietal and premotor/sensory likely to be verbal
zhang et al 2004 fmri and wm
cross modal memory task - recall auditory digits and visual location (ep. buffer)
distributed activity in bilateral PFC, right premoor, temporoparietal junction and left superior parietal junction
distributed activity reflect integrated function of ep buffer
cohen et al 1997 fmri on wm
fmri on phon loop recall of psuedorandom sequence of constenants with target letter at end - in sequence?
DLPFC - exec function
posterior and inferior frontal cortex - broccas assoc with articulatory control process
+ posterior parietal cortex
nystrom et al 2000 fmri
fmri on phon and visuospatial via verbal/non verbal and spatial/non spatial tasks ie nbacks for letter - v ns shapes - nv ns location - nv s
looking for left/right PFC verbal/nonverbal dissociation
dorsal/ventral spatial/nonspatial dissociation for WM
no evidence for v/nv or s/ns dissociatinos between areas - unlikely to have representational organisation within the wm
how does the PFC develop
increase in volume throughout childhood and adolescence
allow dev of cog abilities
steady linear increase from 6years
- change quantitative (Amount can do/hold) but not qualitative (Way info is processed)
kingberg PFC development
older children/teens show increase activity in intraparietal cortex and posterior superior frontal sulcus during spatial wm tasks
DTI - white matter maturation correlate with wm dev
pos corr with wm dev and activation in forntal and parietal regions
fuster et al 2001 LTM AND WM
Acquisition of new memory cannot take place without retrieval of old memory
New memories consist invariably of the update and expansion of old ones, which activates associative recognition and recall
perceptual memory (recall of episodes) = behaind central sulcus frontal cortex for executive memory (planning and co ord)
describe the medial temp lobe
interconnected structures related to Declarative memory-
The system consists of the
hippocampal region
amygdala
adjacent perirhinal, entorhinal, and parahippocampal cortices
PFC and medial temporal lobe interactions in long-term
fuster and alexander 1971 pfc and wm
pfc cells fire at persistent high rates when retaining visual info in STM during delayed response task
remeber no location in field in accordance to order of presentation (ie corsi blocks)
“memory cells” - increase firing during delay increase firing dring delay - cells involved in the retention of ST info in the inferotemporal cortex
PFC activate in preparation for action following delay after cue
bates et al 1994
temp lobe connect to inf PF visual WM
domain specific organisation of PFC -
ventral “what” involved in mneumonic processing ie objects and faces via IT
dorsal “where” involved in spatial processing via posterior parietal and dlPFC
goldman-rakic and friedman 1991
PFC hipp and parietal regions in wm
hipp in memory consolidation
activated along with PFC in wm
posterior transmit visuospatial to dlPFC
jonides et al 1993 wm brain areas in PFC
macaque brain acivity in wm tasks show corresponding activity across regions and species spatial wm: mid frontal gyrus dlPFC - PET human support
salmon 1996 tasks linksed to wm
central exec - letter updating
visospatial - item recall
phonological - recall dissimilar constonants
episodic - cross modal memory task
milner 1968 patient hm and ltm
ltm assoc with hippocampal formation
hm severe aterograde amnesia due to bilat lesions to medial temp lobes including hipp
show improvement in perceptual memory of motor tasks despite lack of recall - hipp NOT link to procedural - episodic
nadel and moscovich 1997 standard model of the hopp
consolidate memory in the neocortex - info bind to memory trace via hipp, MTL and diecephalon
ST consolidation then LT
hipp in primary consolidation by encoding all attended info - until neocortex sustains permanent memory trace into LTM
hipp and neocortex interact overtime bimodally
simon and spears 2003 MTL
MTL = storage and retrieval of LTM
PFC = select, engage, monitor and inhibit in cog control tasks
PFC top cown control of encding, elaborating on representations in MTL based on goals and task demands
