Lecture 8: Parietal Lobes & Attention Flashcards
Posterior Parietal Cortex
parietal areas PE, PF, and PG lying posterior to the primary somatosensory areas
Saccade
a series of involuntary, abrupt, and rapid small movements or jerks of both eyes
Sensorimotor Transformation
neural calculations that integrate the movements of different body parts (eyes, body, arm, etc.) with the sensory feedback of what movements are actually being made and the plans to make the movements
depends on both movement-related and sensory-related signals produced by cells in the posterior parietal cortex
Acalculia
inability to perform mathematical operations
Stereognosis
tactile perception
recognition of objects through the sense of touch
Afferent Paresis
loss of kinesthetic feedback that results from lesions to the postcentral gyrus (areas 3-1-2) and produces clumsy movements
Astereognosis
inability to recognize the nature of an object by touch
Simultaneous Extinction
the somatoperceptual disorder most commonly associated with damage to the secondary somatic cortex (areas PE and PF), especially in the right parietal lobe
two stimuli would be reported if applied singly, but only one would be reported if both were applied together
the second stage of recovery from contralateral neglect characterized by response to stimuli on the neglected side as if there were a simultaneous stimulation on the contralateral side
Numb Touch
a tactile analogue of blindsight, in which individuals have lost tactile perception but are able to locate objects through touch
Asomatognosia
loss of knowledge or sensory awareness of one’s own body and bodily condition
may be on one or both sides of the body
most commonly results from damage to the right parietal lobe
Anosognosia
loss of ability to recognize or to acknowledge an illness or bodily defect
usually associated with right parietal lesions
Anosodiaphoria
indifference to illness
Autopagnosia
inability to localize and name one’s own body
Asymbolia for Pain
inability to understand the meaning of or react to pain
Contralateral Neglect
neglect of part of the body or space contralateral to a lesion
Allesthesia
a stage of recovery from contralateral neglect characterized by a person’s beginning to respond to stimuli on the neglected side as if the stimuli were on the unlesioned side
Agraphia
decline in or loss of the ability to write
Apraxia
the inability, in the absence of paralysis or other motor or sensory impairment, to make or copy voluntary movements, especially an inability to make proper use of an object
Ideomotor Apraxia
an inability to use and understand nonverbal communication such as gesture and pantomime or to copy movement sequences
Constructional Apraxia
a visuomotor disorder in which spatial organization is disturbed
Disengagement
the process by which attention is shifted from one stimulus to another
Attention
a selective narrowing or focusing of awareness to part of the sensory environment or to a class of stimuli
Conjunction Speech
a concept in attentional theory that assumes the existence of a mechanism with which the sensory system searches for particular combinations of sensory information
Feature Search
a cognitive strategy in which sensory stimuli are scanned for a specific feature, such as color
Sensory Neglect
a condition in which an organism does not respond to sensory stimulation
What is the anterior parietal lobe?
primary somatosensory cortex
What is the posterior parietal lobe?
association cortex
What are the behavioral uses of spatial information?
movement guidance (e.g., reaching/grasping): with object recognition
sensorimotor transformation: “body now” to “body future”
spatial navigation
math
language (syntax)
What are symptoms of parietal damage?
high sensory thresholds: takes much more intense stimulation before they detect
astereognosis
asomatognosia: loss of awareness of ownership of a body part (e.g., arm, leg)
dyscalculia/acalculia
disturbed language function: angular gyrus, organization of letters, syntax of words
apraxia (e.g., ideomotor)
simultaneous extinction
What is apraxia?
can’t mimic or repeat actions
once they are given tool, they can do it
problems sequencing motor actions
What is simultaneous extinction?
damage to the right posterior region of the parietal lobe
when shown two identical objects: patient sees only the object in his right visual field
when shown two different objects: patient sees the object in both visual fields
when shown two kinds of an object: patient sees only the object in his right visual field
What is attention?
alternes and arousal
vigilance
selective attention
orienting
effort and resource capacity: mental workload and task difficulty
sensory specific processes
What is Posner’s attention switching paradigm?
focus on the middle, one box will light up, participants are told that cue is meaningless; target could come on same side or opposite as que
valid cue is shown 80% of the time, invalid cue shown 20%
there is a longer reaction time for the invalid cue
requires a switch; disengage, move, re-engage
parietal, superior colliculus, thalamus
What are symptoms of posterior parietal lobe damage?
contralateral neglect
hemi-inattention
ignores or cannot attend to one side of space: contralateral, body midline, multisensory, double simultaneous stimulation technique
What is contralateral neglect?
lesion most often in right inferior parietal lobe: right intraparietal sulcus and right angular gyrus, occasionally noted after lesions to frontal lobe and cingulate cortex
defective sensation or perception
defective attention or orientation
What is extinction?
clinical sign: easy to test, doesn’t take much assessment
patients detect single stimulus
either ipsi- or contralesional side of body
presenting singular may not reveal deficit
fail to detect contralesional stimulus when concurrent stimulus presented on ipsilesional side
What is the line bisection task?
ask “draw a line that cuts this line in half”
ignore left, can quickly tell they can’t see left side
performance improves with spatial cue, drawing attention to left side
this suggests that there is a problem with attending to left side
What is the prism effect?
without prisms, F.D.’s copy of the drawing showed complete neglect of the left side
F.D. then examined the drawing for 5 minutes while wearing prisms
copies made as much as 2 hours later showed attention to items in the left visual field
focuses and engages other areas of the brain that are still intact to help with attentional shifting
What is the Bisiach & Luzzatti (1978) plaza experiment?
looking at two stroke survivors with extensive parietal damage; both know area pretty well
imagine yourself at far end of the plaza; tell me all the landmarks you see; only said landmarks that are in their right visual field
now imagine yourself at the other end facing the other way; still only say the landmarks on their right
they know there are landmarks on the left, but only say one’s on their right
hemineglect is internal, attention must be required to recall things
What are the conclusions of the plaza experiment?
memory intact
left-side neglect
not externally driven
attention may be required to recall things
attention and memory are intimately linked
disengagement problem: have trouble disengaging their attention from the right side unless you help to cue them
What are the findings of neurophysiological studies on peripersonal space?
brain areas specialized for coding of visual space surrounding body
cells in parietal & frontal cortices, as well as putamen; respond to visual stimuli in spatial proximity to particular body part (e.g., face or hand)
bimodal - respond to visual & tactile stimuli (VS, TS)
receptive fields for visual stimuli match those for tactile on body surface - even when limb and eyes move
suggests these brain regions part of interconnected system for integrated coding of peripersonal space centered on body parts
What was the study of right parietal damage patients with tactile extinction in the peripersonal space of their arms?
left tactile extinction was shown when both arms were touched
left tactile extinction also occurs with an ipsilesional visual stimulus near hand, same degree as tactile
however, far less extinction when visual stimulus presented away from space around hand (anchored to hand)
What was the study of right parietal damage patients with tactile extinction in the peripersonal space of their face?
left tactile extinction when both sides of face were touched
left tactile extinction also occurs with an ipsilesional visual stimulus near face, same degree as tactile
far less extinction when visual stimulus presented away from face
suggests crossmodal system exists for hands and face
What was the study on is peripersonal space can be modified through tool use?
baseline: minimal extinction pre-tool
extinction greater immediately after tool use and when tool in hand
back to baseline after 5 minute delay
immediate pointing did not lead to extinction
system has dynamic properties that may relate to development of tool use in humans & other primates
What are the triad of symptoms in Balint’s syndrome?
simultagnosia: cannot recognize more than 1 object at a time
optic ataxia: deficit in visually-guided reaching
oculomotor apraxia: difficulty directing saccades to an object of interest, difficulty in breaking fixation from that object
What causes Balint’s syndrome?
bilaterally
region that has been described as “vision for action”
