Download Let`s Get to Know the Parietal Lobes!

Let’s Get to Know the
Parietal Lobes!
A brief primer on parietal lobe function (as it relates to memory).
By Rebecca Emily Martin
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Brodmann Areas associated
with parietal lobes
BA 3, 1, 2, 5 - somatosensory
BA 7 - visuo-spatial imagery , selfprocessing
BA 23, 29, 31 - Retrosplenial cortex,
posterior cingulate
BA 39 - reading, visuo-language
processing
BA 40 - supramarginal gyrus
BA 43 - parietal operculum
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The Parietal Lobes can be
divided into 6 main regions
lateral
medial
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The Parietal Lobes can be
divided into 6 main regions
dorsal
ventral
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The Parietal Lobes can be
divided into 6 main regions
posterior
anterior
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The Parietal Lobes can be
divided into 6 main regions
posterior
(This presentation
focuses on posterior
parietal cortex, PPC)
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Terminology
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Terminology
Lateral Posterior Parietal
Cortex (PPC)
Includes two main regions
separated by the
intraparietal sulcus (IPS)
superior parietal
lobule (SPL)
inferior parietal lobule
(IPL)
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Terminology
superior parietal
lobule
aka
dorsal posterior parietal
cortex
aka
BA 7
(and sometimes BA 5
aka the association
cortex)
aka
the precuneus
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Terminology
inferior parietal lobule
aka
ventral posterior parietal cortex
aka
BA 39 and BA 40
aka
the angular and supramarginal gyri
which also include
the temporoparietal junction
Wernicke’s area
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Terminology
Other notable areas:
posterior cingulate
cortex, BA 23, 31
(PPC)
retrosplenial cortex,
BA 29 (Rsp, or RSC)
parietal operculum
(but we won’t talk
about this part)
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somatosensory
senso
r
integr y
ation
g
din
rea
ua g e
lang nsion
e
preh
com
theory of mind
self-processing
Function of Lateral Regions
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Notable Networks
default network
frontoparietal control system
dual attentional processes hypothesis (Cabeza, 2008)
dorsal parietal attention system
ventral parietal attention system
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Default Network
Key Regions:
Posterior cingulate/Retrosplenial
Cortex (considered a hub)
Inferior parietal lobule
Medial Prefrontal Cortex
hippocampus
lateral temporal cortex
Has inverse relationship with cognitive
control networks.
Associated with autobiographical memory
Buckner et al., 2007
Red = default network
Blue = cognitive control networks
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Familiarity
Dual Attentional Processes
Hypothesis of attention to Memory
Recollection
Dorsal PPC
includes SPL and IPS
top-down, preparatory, goaldriven allocation of attention
Ventral PPC
includes IPL and TPJ
bottom-up, reflexive
reorienting of attention to
behaviorally relevant
information
Cabeza, Nat Rev Neuro 2008
c
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dorsal attention system (similar to dorsal attn.
network)
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40
40
39
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Familiarity
Recollection
red - familiar
blue - remember
Low-confidence recognition
High-confidence recognition
Figure 4 | Ventral–dorsal dissociations in activity. a | In a functional MRI (fMRI) study of the remember–know
paradigm60, the ventral parietal cortex (VPC) showed greater activity for remember than for know trials, whereas the
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dorsal parietal cortex (DPC) showed the opposite pattern. b | In an fMRI study of confidence during
memory6
the VPC showed greater activity for high- than for low-confidence hits, whereas the DPC showed the opposite pattern.
c | A meta-analysis of parietal activity during episodic retrieval. The images plot the peaks of activations in two kinds of
event-related fMRI studies (for a list of studies and coordinates, see Supplementary information S3 (table) and S4 (table)).
A first group of peaks (red and dark blue dots) is from studies that identified activity related to recollection or familiarity b
using the remember–know paradigm, by distinguishing successful from unsuccessful source-memory retrieval, or by
comparing the retrieval of items encoded under deep versus shallow study tasks48,49,51,58,59,96,100–102,109–118. A second group of
peaks (yellow and pale blue dots) is from studies that investigated recognition confidence61,62,81,119. In general, recollection
and high-confidence recognition were associated with VPC activations, whereas familiarity and low-confidence
recognition were associated with DPC activations. Part a modified, with permission, from REF. 60 ’ (2006) American
Physiological Society. Part b modified, with permission, from REF. 63 ’ (2007) Pergamon Press.
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began as soon as the search instructions were given and
continued throughout the search period, whereas VPC
activity was greater than DPC activity when the target
was detected66. Thus, DPC activity mediates preparatory
top-down attention, whereas VPC activity is associated
with the capture of bottom-up attention by behaviourally relevant stimuli. Activity that is associated with bottom-up attention can also be captured using unexpected
(spatial and non-spatial) stimuli67–72. When a relevant
stimulus that was out of the current attentional focus
appears, the VPC sends a ‘circuit breaker’ signal to the
DPC, which shifts attention to the previously unattended
Fronto-parietal Control Network
Three key networks:
High-confidence
recognition
stimulus73. The right VPC is also the most frequent loca
tion of lesions that cause neglect, which can be describe
as a deficit in bottom-up attention: patients with negle
can voluntarily direct attention to the contralesional sid
and can use cognitive cues to anchor attention to the le
visual space, but they have a deficit in detecting stimu
that are outside the focus of ongoing processing23.
Parietal cortex, attention and episodic memory
Could the distribution of episodic-retrieval activation
in FIG. 4c be associated with the allocation of top-dow
and bottom-up attention to memory by the DPC and th
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superior parietal lobule, intraparietal lobule,
intraparietal sulcus, MT+, ventral premotor
cortex and frontal eye fields
Hippocampal-cortical memory system (similar to
ventral attn. network/ default network
declarative memory (e.g. autobiographical)
inferior parietal lobule, retrosplenial cortex,
posterior cingulate, ventromedial PFC, lateral
temporal lobe
fronto-parietal control system
anatomically interposed between the two
systems: anterior PFC, dorsolateral PFC,
anterior cingulate, anterior insula, anterior
inferior parietal cortex
mediates the dorsal attn. and hippocampalcortical memory systems
Vincent et al., J. Neurophysiol 2008
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Memory and the Parietal Lobes
Encoding (Uncapher and Wagner, 2009)
In a remember/know task:
successful remembering was associated with dorsal PPC
i.e. the more you “pay attention” during a task, the more
likely you are to remember something
forgetting associated with ventral PPC
i.e. if you are “spacing out” your default network is probably
more active, and you are less likely to remember...
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Memory and the Parietal Lobes
Retrieval (Hutchinson, Uncapher, Wagner, 2009)
theories out there but no certainty...more research needed
doesn’t mirror the dual attention hypothesis
main conclusion: attentional mechanisms more involved in
encoding than in retrieval
Successful remembering associated with ventral regions
while less successful remembering associated with dorsal
regions
dorsal system primarily left-lateralized
specialized role for IPS? (visual mapping)
ventral system primarily right-lateralized (spatial
reorienting)
default network also part of the ventral system
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Don’t forget the medial
parietal regions!
Retrosplenial Cortex (Rsp or RSC)
considered an intermediate “translation” zone
involved in hippocampal-dependent function (many
reciprocal connections with MTL regions) (Vann, Nat Rev
Neuro, 2009)
Posterior Cingulate Cortex (PCC)
considered hub of the default network
“evaluative” region (as opposed to being an “executive”
region like the ACC) (Vogt, Cerebral Cortex, 1992)
Precuneus
activated during source memory retrieval along with lateral
PPC (Cavanna, Brain, 2006)
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REVIEWS
ATN
Head direction,
theta
Prefrontal cortex
Executive, scene manipulation
Parietal cortex
Body-oriented information
Egocentric
framework
Retrosplenial cortex
Scene translation
Perirhinal cortex
Object-based information
Occipital cortex
Visual information
Hippocampus
Event within a scene,
scene construction
Parahippocampal
Scene-based
information
Allocentric
framework
Figure 3 | The key anatomical and functional relationships of the retrosplenial cortex. Effective episodic
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memory, navigation and future thinking all require the ability to integrate and manipulate
different
frameworks
of
information, for example egocentric (self-centred) and allocentric (world-centred) frameworks. By virtue of its
principal connections, the retrosplenial cortex is uniquely placed to enable translation within these domains.
ATN, anterior thalamic nuclei.
key questions could be addressed by assessing patients
with RSC damage on their ability to imagine fictitious and future experiences and on how they process
scenes, and by using fMRI studies with task designs
been the poor relation of cognitive neuroscience. It is
our hope that the RSC will now become a major focus
of dedicated research, and our belief that defining its
role will prove pivotal in understanding a range of
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