Occipito-Parietal Segment

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

    Vision Pathways

    Overview Videos All Segments Considered Optical Segment Prechiasmal Segment Chiasmal Segment Retrochiasmal Segment Occipital-Parietal Segment Occipito-Temporal Segment