Visual Tracts Flashcards
What forms the visual pathway?
Axons of ganglion cells from rods and cones
Visual field
Area that a person is able to see when both eyes fixed
Retinal field
The image on the retina (inverted)
Binocular zone
Central region seen by both eyes
Monocular zone
Peripheral zone seen only by 1 eye
Left half of visual field forms image on:
Nasal half of left retina
Temporal half of right retina
Right half of visual field forms image on:
Nasal half on right retina
Temporal half of left retina
Nasal half goes:
CL
Temporal half goes:
IL
Optic tract includes fibers from:
Temporal half of IL eye
Nasal half of CL eye
Where do the optic tracts terminate?
Lateral geniculate nucleus
Ventral base of LGN is from:
Dorsal and lateral borders of LGN are from:
Ventral base of LGN is from: optic tract (reticulogeniculate)
Dorsal and lateral borders of LGN are from: outgoing optic radiations
Magnocellular (M) layers
Layers 1 and 2.
Large cells
Receive info from rods.
Parvocellular (P) layers
Layers 3 to 6.
Small cells.
Receive info from cones.
Temporal retina stay ____ and terminate in layers:
IL and terminate in layers 2, 3 and 5.
Nasal retina goes ____ and terminate in layers:
CL and terminate in layers 1, 4 and 6.
Same point in visual space is represented ___ times.
- One for each layer of LGN. Optic tract branches.
What goes from LGN to calcarine sulcus?
Geniculocalcarine (geniculostriate) pathway
Lower quadrant of CL hemifields target:
Superior bank of calcarine sulcus, the cuneus.
Upper quadrant of CL hemifields target:
Inferior bank of calcarine sulcus, the lingual gyrus.
Meyer loop
A U-turn that fibers from the upper quadrant of CL fibers take to get to the lingual gyrus.
Where does the visual pathway end?
Striate cortex (Broadmann’s area 17).
Visual association cortex is composed of which areas:
Area 18 and 19. PTO area.
Superior colliculus is important in:
Directing eye movements
Pretectal area is important in:
Pupillary light reflex
Hemianopia
Blindness in one half of visual field
Homonymous visual field
Heteronymous visual field
Homo: visual field losses is similar in both eyes.
Hetero: 2 eyes have non-overlapping field losses.
Macular sparing
Visual field loss that preserves vision in center of visual field
Congruent deficit
Incongruent deficit
Deficit is symmetric
Deficit is asymmetric
Damage anterior to chiasm affects:
Only IL eye
Damage at the chiasm causes:
Heteronymous defects
Damage posterior to chiasm causes:
Homonymous defects
Associative visual agnosia cause:
What can/can’t they do?
Infarction in left occipital lobe and posterior corpus callosum, usually from occlusion of PCA.
Disconnects language area from visual association cortex.
Pt cannot name or describe an object, but can recognize/demonstrate its use.
