Week 1: Chapter 14 - The Parietal Lobes Flashcards
What is the main function of the parietal cortex?
Processing and integrating somatosensory and visual information for movement control.
Where is the parietal cortex located?
Between the frontal and occipital lobes, under the parietal bone.
What structures demarcate the parietal lobe?
Central fissure (anterior), Sylvian fissure (ventral), cingulate gyrus (dorsal), parieto-occipital sulcus (posterior).
What does the postcentral gyrus do?
Processes touch and bodily sensations.
What is the role of the superior parietal lobule?
Integrates sensory input, especially for movement coordination.
What does the parietal operculum process?
Somatosensory information.
What are the functions of the supramarginal and angular gyri?
Language, spatial processing, and visual-motor coordination.
What are the two functional zones of the parietal lobe?
Anterior (somatosensory cortex) and posterior (higher-order visuospatial processing).
Which areas of the human brain are expanded relative to other primates?
PG and STS.
What is the function of polymodal neurons in PG?
Integrate somatosensory and visual input.
Which hemisphere shows larger PG and STS areas?
Right hemisphere.
What does left hemisphere PG specialization support?
Language and specific spatial impairments when damaged.
What does the lateral intraparietal area (LIP) control?
Saccadic eye movements.
What does the anterior intraparietal area (AIP) control?
Object-directed grasping.
What is the role of the parietal reach region (PRR)?
Coordinates visually guided reaching and grasping.
Where does the anterior parietal cortex project?
To PE, primary motor, supplementary motor, and premotor areas.
What is the role of PE?
Somatosensory integration and limb movement guidance.
What does PF integrate?
Sensorimotor input from PE, motor areas, and some visual input.
What does PG integrate?
Multimodal input including visual, somatosensory, auditory, and vestibular signals.
How is the parietal cortex linked to executive function?
PG and PF connect to the dorsolateral prefrontal cortex.
What are the three dorsal stream pathways identified by Kravitz et al.?
Parieto–premotor, parieto–prefrontal, and parieto–medial temporal.
What is the parieto–premotor pathway responsible for?
Visually guided actions like reaching and grasping.
What does the parieto–prefrontal pathway support?
Visuospatial cognition and working memory.
What does the parieto–medial temporal pathway facilitate?
Spatial navigation and environmental mapping.
What additional regions connect with the dorsal stream?
V5 and superior temporal sulcus (STS).
What is the primary function of the dorsal stream?
Guiding visuospatial behavior through motor output.
What are the two main zones of the parietal lobe and their functions?
Anterior zone processes somatic sensations and perceptions; posterior zone integrates sensory input for movement and mental imagery.
What does the posterior parietal cortex primarily do?
Integrates sensory input for reaching, grasping, whole-body movement, and mental imagery.
Is there a single spatial map in the brain?
Unlikely; instead, there are multiple spatial representations tailored to different behavioral needs.
What are the two types of spatial processing highlighted by Milner and Goodale?
Spatial processing for object recognition and for guiding movement.
How is visuomotor control (viewer-centered) different from object recognition (object-centered)?
Visuomotor control guides movement based on the viewer’s perspective, while object recognition identifies objects regardless of viewpoint.
What controls eye movements in visuomotor tasks?
Frontal eye fields.
What controls limb movements in visuomotor tasks?
Premotor and supplementary motor areas.
What role does the posterior parietal region play in movement?
Guides eye and limb movements and supports short-term spatial memory.
What two key features did John Stein identify in posterior parietal neurons?
Integration of sensory, motivational, and motor inputs; increased activity with attention or movement toward a target.
What is sensorimotor transformation?
The process of integrating sensory feedback and movement plans to guide actions.
What did Richard Andersen discover about the parietal reach region (PRR)?
It encodes movement goals rather than specific movement details.
What are brain-computer interfaces (BCIs)?
Technologies allowing control of robotic limbs or devices via neural activity.
What did Nicolelis demonstrate with brain-to-brain communication?
Neural activity from one rat could influence behavior in another, enabling potential real-time sensorimotor sharing.
What brain regions are involved in spatial navigation?
Medial parietal region (MPR), posterior cingulate cortex, and PRR.
What did Sato’s research on MPR show?
MPR neurons respond to movement at specific locations and are crucial for navigation.
How do PRR and MPR cells differ in function?
PRR controls limb movement planning; MPR controls body movement to locations.
What spatial concepts are impaired by posterior parietal damage?
Distinguishing left from right, spatial reasoning, and mental image manipulation.
How does the parietal lobe contribute to visual imagery?
It enables the mental manipulation and reorientation of objects.
What is acalculia?
Difficulty performing arithmetic due to parietal lobe damage.
How is language spatial in nature?
Word order conveys meaning, and damage can impair understanding syntax.
Where is the polysensory region involved in language and math located?
At the temporoparietal junction.
What motor deficit is caused by parietal lobe damage?
Difficulty in planning or sequencing motor actions.
What happens when the postcentral gyrus is damaged?
It raises somatosensory thresholds and impairs touch localization, especially on the contralateral side.
What is afferent paresis?
Clumsy movements caused by loss of kinesthetic feedback due to S1 lesions.
Who studied sensory deficits in WWII veterans and epilepsy patients?
Josephine Semmes and Suzanne Corkin.
What is astereognosis?
Inability to recognize objects by touch despite normal basic sensation.
What is simultaneous extinction?
Failure to perceive one of two stimuli when touched simultaneously.
Which areas are typically damaged in simultaneous extinction?
Areas PE and PF, especially in the right parietal lobe.
What is numb touch (or blind touch)?
Ability to localize touch without conscious tactile sensation.
What did Jacques Paillard’s 1983 study demonstrate?
A woman with right-side anesthesia could localize touches without feeling them.
What does numb touch suggest about tactile processing?
There are separate systems for detection and localization of touch.
What is asomatognosia?
Loss of awareness of one’s own body or condition.
What is anosognosia?
Unawareness or denial of illness.
What is anosodiaphoria?
Indifference to illness.
What is autopagnosia?
Inability to localize or name body parts.
What is asymbolia for pain?
Lack of typical reactions to pain.
Which hemisphere is usually affected in asomatognosia?
The right hemisphere, except autopagnosia linked to the left parietal cortex.
What is finger agnosia?
Inability to identify or point to one’s fingers.
What condition is finger agnosia associated with?
Dyscalculia (difficulty with arithmetic).
Why is finger agnosia linked to math difficulties?
Because finger-based counting aids early numerical learning, and loss of this impairs arithmetic.
What are the three main symptoms of Bálint’s syndrome?
- Impaired visual fixation, 2. Simultagnosia, 3. Optic ataxia
Which area is typically damaged in optic ataxia?
Superior parietal region (area PE)
What is contralateral neglect and what brain area is typically involved?
A condition where patients fail to attend to the left side of space/body, typically from right parietal damage (angular gyrus, intraparietal sulcus)
What are the two stages of recovery from contralateral neglect?
- Allesthesia, 2. Simultaneous extinction
What are the two main theories explaining neglect?
- Defective sensation/perception, 2. Defective attention/orientation
What is Gerstmann syndrome and what area is affected?
Includes finger agnosia, right-left confusion, agraphia, and acalculia; associated with damage to the left angular gyrus (area PG)
What type of apraxia is strongly associated with left parietal lesions?
Ideomotor apraxia
What does constructional apraxia affect?
Ability to assemble, draw, or mimic spatial tasks; can result from left or right parietal lesions
What role does the parietal lobe play in drawing?
Right parietal damage affects spatial organization; left parietal damage affects conceptual and motor execution
What is the function of the parietal cortex in attention?
Shifting or disengaging attention between stimuli (selective attention)
What hemispheric differences exist in spatial cognition?
Left hemisphere: generating mental images; Right hemisphere: manipulating mental images
What deficits result from right inferior parietal or STS damage?
Topographic disorientation and spatial orientation problems
What symptom is commonly shared between left and right parietal damage?
Constructional apraxia and spatial cognition disorders
What is the cognitive mode preference theory?
Individuals process spatial problems verbally or nonverbally; damage to the preferred hemisphere leads to atypical impairments
What do anterior parietal-lobe lesions typically cause?
Somatosensory impairments (e.g., in area PE).
What do posterior parietal-lobe lesions typically cause?
Higher-order cognitive and spatial dysfunctions.
What is the purpose of standardized neuropsychological tests in parietal-lobe assessment?
To predict the location and extent of damage.
Which test is used to assess somatosensory thresholds?
Two-Point Discrimination Test.
How is the Two-Point Discrimination Test conducted?
A blindfolded subject identifies one or two points touching their skin.
Which areas affect tactile recognition when lesioned?
Areas PE and PF.
Which test evaluates tactile form recognition?
Seguin–Goddard Form Board Test.
What additional ability does the Seguin–Goddard test assess?
Memory and cross-modal matching (involving area PG).
Which test is used to diagnose contralateral neglect?
Line-Bisection Test.
What behavior indicates contralateral neglect in the Line-Bisection Test?
Misplaced midpoints toward the right or ignoring left-sided lines.
Which tests assess visual gestalt perception?
Mooney Closure Faces Test & Gollin Incomplete Figures Test.
What deficit do the Mooney and Gollin tests reveal?
Impaired gestalt perception (linked to right temporoparietal damage).
Which test evaluates spatial orientation and body part distinction?
Right-Left Differentiation Test.
What symptoms are associated with left parietal damage in spatial relation tasks?
Right-left confusion.
What does the Token Test evaluate?
Language comprehension.
What does poor performance on the Token Test suggest?
Aphasia, especially when area PG is lesioned.
Which test evaluates motor planning deficits in apraxia?
Kimura Box Test.
What movements are involved in the Kimura Box Test?
Pushing a button, pulling a handle, pressing a bar.
Why is behavioral observation important in apraxia diagnosis?
Because no fully standardized test for apraxia exists.
