Parietal Lobes Flashcards
(24 cards)
- What are the subdivisions of the parietal cortex and its main connections?
The parietal cortex is divided into the anterior zone (somatosensory cortex: Brodmann areas 3-1-2 and 43) and the posterior zone, which includes the superior parietal lobule (areas 5 and 7, including the precuneus) and the inferior parietal lobule (supramarginal gyrus – area 40, angular gyrus – area 39). Major connections include projections to premotor, prefrontal, and medial temporal regions, supporting movement, spatial navigation, and working memory.
What are the key pathways of the dorsal stream and their functions?
Parieto–premotor pathway: guides movements (“how” pathway)
Parieto–prefrontal pathway: supports visuospatial working memory
Parieto–medial temporal pathway: supports spatial navigation via connections to the hippocampus and cingulate cortex
What are the behavioral uses and complexities of spatial information?
Spatial info helps with both object recognition (allocentric coding) and movement guidance (egocentric coding). Complex tasks like mental rotation, arithmetic, syntax, and sequential planning also rely on parietal spatial processing.
What roles do the parieto–premotor, parieto–prefrontal, and parieto–medial-temporal pathways serve?
High sensory thresholds, Afferent paresis, Astereognosis (inability to identify objects by touch), Simultaneous extinction, Numb touch (tactile blindsight)
What brain regions are included in the dorsal stream for spatial behavior?
Optic ataxia, Contralateral neglect, Constructional and ideomotor apraxia, Gerstmann syndrome, Drawing and spatial attention deficits, Object recognition problems from unfamiliar views
What disorders fall under spatial cognition?
Mental rotation deficits
Map reading/topographic disorientation
Poor spatial memory
Difficulty navigating familiar environments
How do the left and right parietal lobes compare?
Left parietal lobe: More involved in language, calculation, writing, and ideomotor planning
Right parietal lobe: Specialized in spatial attention, navigation, constructional apraxia, and neglect
What tools are used for clinical neuropsychological assessment of parietal damage?
Two-point discrimination (sensory threshold)
Seguin–Goddard Form Board (tactile object recognition)
Line bisection test (neglect)
Mooney faces / Gollin figures (visual perception)
Right-left discrimination tests
Kimura Box (apraxia)
Token test (language comprehension)
Why is the expansion of PG and STS in humans significant?
These polymodal areas process visual, auditory, and tactile inputs, supporting complex behaviors like tool use, spatial reasoning, reading, and social interaction. Their asymmetry (especially in PG) explains the different symptoms in right vs. left parietal lesions.
How does the parietal cortex help in object recognition and movement guidance?
Recognition uses object-centered cues (e.g., shape, size, color)
Guidance relies on viewer-centered cues (e.g., direction, location)
The brain uses the need-to-know principle, only using detail when necessary.
How do posterior parietal neurons respond to visual stimuli?
Neurons show low activity for passive viewing but high activity when attention is focused or movement is planned. They respond to both sensory and motor inputs, supporting sensorimotor transformation.
What did Andersen’s experiments reveal about thought and intention?
Monkeys trained to reach showed PRR neurons firing during movement planning — even when no movement occurred. This suggests the parietal cortex encodes goals and intentions, not just actions.
What evidence links spatial cognition to brain anatomy?
fMRI studies show that parietal lobe volume and activation levels correlate with spatial skills.
PG and STS regions are more developed in individuals with stronger spatial cognition abilities.
What’s the difference between astereognosis and simultaneous extinction?
Astereognosis: Can’t identify objects by touch alone
Simultaneous extinction: Can’t detect one of two simultaneous stimuli even though both are perceived alone
What are the four symptoms of Gerstmann syndrome and the lesion site?
Agraphia, acalculia, right-left confusion, finger agnosia; lesion in left angular gyrus (area PG).
What are the two stages of recovery in contralateral neglect?
Allesthesia: Stimuli on the neglected side are perceived on the non-neglected side
Simultaneous extinction: The patient detects both sides only when stimulated individually
What are four deficits more likely with right-parietal damage?
Contralateral neglect
Constructional apraxia
Topographic disorientation
Deficits in mental rotation/map reading
What is Bálint syndrome?
A rare condition from bilateral parietal damage characterized by optic ataxia, simultagnosia, and inability to fixate on visual targets.
What is the difference between ideomotor and constructional apraxia?
Ideomotor: Difficulty copying or performing gestures (left parietal)
Constructional: Difficulty drawing or assembling objects (either hemisphere)
What are examples of asomatognosia symptoms?
Anosognosia: Denial of illness
Autopagnosia: Can’t name/localize body parts
Asymbolia for pain: Doesn’t react to pain
What is the temporal–parietal junction (TPJ) involved in?
Attention, memory, language, social cognition, and self-awareness. It includes the supramarginal gyrus, angular gyrus, STS, and STG.
What is the parietal memory network (PMN)?
Includes the precuneus, angular gyrus, and midcingulate cortex. It supports memory retrieval, especially for familiar stimuli.
What is the Kimura Box Test used for?
To diagnose apraxia by having patients perform a sequence of motor actions (push, pull, press).
What does the Mooney Faces or Gollin Incomplete Figures test assess?
These assess visual perceptual integration by asking subjects to identify faces or objects from fragmented images — often impaired after right temporoparietal damage.
