Occipito-Parietal Segment
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Visual pathway segment that conveys visual signals from primary visual cortex to vision-associated parietal cortex (“dorsal stream”)
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Carries visual signals from primary visual cortex to parietal vision-associated cortex for integration with auditory, somatosensory, and limbic inputs
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Integrates attentional and visuo-spatial function
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Unilateral lesions
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Hemispatial neglect
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Lack of awareness of visual, auditory, and somatosensory stimuli in contralateral hemispace
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Reduced motor activity in contralateral hemispace
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Loss of awareness of own contralateral body parts
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Gaze deviation or gaze preference toward the side of the lesion
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Lesions usually in the right cerebral hemisphere
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Common acute cause: ischemic or hemorrhagic parietal lobe stroke
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Bilateral lesions
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Balint-Holmes syndrome (global visual inattention)
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Misreaching
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Tentative walking
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Impaired volitional gaze
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Misjudgment of spatial relationships
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Inability to interpret pictures, tell time from analog display
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Common acute cause:
systemic hypotension with “borderzone” (“watershed”) parietal and frontal lobe infarction
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Common chronic cause:
Alzheimer disease
