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Chapter 14-17

PSY318H5 Chapter Notes - Chapter 14-17: Cochlea, Unimodality, Anosognosia


Department
Psychology
Course Code
PSY318H5
Professor
Ayesha Khan
Chapter
14-17

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CHAPTER 14 PARIETAL LOBES
Parietal cortex processes and integrates somatosensory and visual
information, with regard to control of movement
ANATOMY
lies between the frontal and occipital lobes
roughly demarcated anteriorly by the central fissure, ventrally by the
lateral fissure, dorsally by the cingulate gyrus, and posteriorly by the
parietal-occipital sulcus.
Inferior parietal lobe: supramarginal gyrus and angular gyrus
Parietal lobe can be divided into 2 functional zones
oAnterior zone: somatosensory cortex
oPosterior zone: posterior parietal cortex
PG (parietal area G) has visual function and is larger in humans
(especially in the RH).
PE has tactile recognition function
Specific parietal-lobe regions take part in DORSAL STREAM of visual
processing:
ocIPS = intraparietal sucus
control in saccadic eye movements (area LIP) and visual
control of object-directed grasping (AIP)
oPRR = parietal reach regions
Role in visually guided grasping movements
Saccade is a series of involuntary, abrupt and rapid small movements or jerks
made by both eyes simultaneously changing the point of fixation
Anterior parietal cortex has connections from the primary
somatosensory cortex to the PE, as well as motor areas (including
primary motor cortex and supplementary motor and premotor regions)
Motor connections must be important for providing sensory info about
limb position in control of movement
Area PE is a somatosensory area, receiving most of its connections
from primary somatosensory cortex.
oCortical outputs are to the primary motor cortex and to
supplementary motor (SMA) and premotor regions, as well as to
PF
oPlays role in guiding movement by providing info about limb
position
Area PF has heavy input from primary somatosensory cortex, through
area PE.
oReceives inputs from motor and premotor cortex and small
visual input through area PG
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oProvide elaboration on similar info for the motor systems as PE
Are PG receives more-complex connections including visual,
somesthetic (skin responses) proprioceptive (internal stimuli),
auditory, vestibular (balance), oculomotor (eye movement) and
cingulate (motivational)
oA part of the dorsal stream
oRole in controlling spatially guided behaviour with respect to
visual and tactile info
Close relations between posterior parietal connections and the
prefrontal cortex
oTherefore, connections between posterior parietal cortex and
dorsolateral prefrontal regions
oImportant role in control of spatially guided behaviour.
THEORY OF PARIETAL-LOBE FUNCTION
Anterior zone processes somatic sensations and perceptions
Posterior zone is specialized primarily for integrating sensory input
from somatic and visual regions and to other sensory regions, for
control of movement
USE OF SPATIAL INFORMATION
spatial information about the location of objects in the world is needed
both to direct action sat those objects and to assign meaning and
significance to them
spatial information is coded in more than one way
Two types of form recognition
1)Object Recognition: spatial information needed to determine the
relations between objects, independent of what the subjects
behaviour might be, is very different form the spatial information
needed to guide eye, head or limb movements to object.
visuomotor control must be viewer-centered location,
orientation and motion must be relative to the viewer
object characteristics, like colour, are irrelevant to
visuomotor guidance, not needed to guide hand action
brain operates on a need to know basis too much
information can be counter productive
However! Object-centered system must be concerned with
properties such as size, shape and colour and relative
location so object can be recognized in different visual
contexts or vantage points
Details in O-C system are important
2)Guidance of Movement:
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posterior parietal cortex has role in viewer-centered
system
prefrontal region have a role in short-term memory of
location of events in space
most neurons in posterior parietal region are active both
during sensory input and during movement
neurons are sensitive to the features of an object that
determine the posture of the hand during manipulation
neuron responsiveness to movements of the eyes and
location of the eye in its socket
cells detect visual information and then move the eye to
get fine vision of the fovea to examine it
cells are affected by the motivational characteristic of
information such as cue signaling the availability of a
reward
Responses of posterior parietal neurons have 2
characteristics in common
They receive combination of sensory, motivational
and related motor inputs
Discharge is enhanced when an animal attends to a
target or makes a movement toward it
These neurons are therefore well suited to transforming
the necessary sensory info into commands for directing
attention and guiding motor outputs
Blood flow increases preferentially in the posterior
parietal region when subjects direct their attention to
visual targets in the studied spot of the visual field
Posterior parietal region plays a significant role in directing
movements in space and in detecting stimuli in space
Superior parietal cortex plays a role in the control of eye
movements, which has significant implications for PET studies of
oBlood flow to posterior parietal cortex when identifying
different spatial locations is evidence that the DORSAL
stream of processing deals with spatial processing
SENSORIMOTOR TRANSFORMATION: when we move towards an object,
we must integrate the movements of different body parts with sensory
feedback of what movements are actually being made (efference copy) and
plans to make the movements. As we move, locations of our body parts change
and must constantly be updated. Neural calculations are called sensorimotor
transformation.
cells in the posterior parietal cortex produce both the movement-
related and the sensory-related signals to make these
also important in movement planning
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