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