COGS 17 Lecture Notes - Lecture 7: Lateral Geniculate Nucleus, Optic Chiasm, Inferior Temporal Gyrus

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Lec 4B - Vision
Visual crossover
Path that information takes from outside world through visual system
Divide left and right visual field
Right visual field to left eye connects to ipsi-lateral brain
Right visual field to right eye connects to contralateral brain
Left visual field to right eye connects to ipsi-lateral brain
Left visual field to left eye connects to contralateral brain
Only after reaches cortex, is visual field info combined via
corpus callosum
Magnification
Visual cortex (v1)
Topological - preserves spatial relationships
Map of input in v1
But absolute size is not maintained
Fovea is greatly (80x) magnified
Visual Imagery
Activates some of the same areas as actual visual perception
Seeing an elephant far away vs imagining an elephant far away
Visual pathways
Dorsal pathway
where/how (motion and depth)
Parietal pathway
Magnocellular pathway - named after cells in retina
Large ganglions in rods and cones of periphery
From high convergence rods (many:1)
Ventral pathway
who/what (color and detail)
Temporal pathway
Parvocellular pathway - named after cells in retina
Small ganglions in cones of fovea
From low convergence cones (1:1)
optic nerve (axons of ganglions) to LGN (lateral geniculate nucleus) of
thalamus
Optic chiasm is where “cross-over” of optic nerves occur
Each LGN has 6 layers
Divisions within LGN
Magnocellular pathways are layers 1 and 2
Parvocellular pathways are layers 3-6
Layers also organized by which EYE (L or R) is
dominant in layer
Some axons along the magnocellular pathway go first to the superior
colliculus (not straight to the LGN) in the tectum of the midbrain
Used in coliculu to map location of visually moving stimuli
Implicated in “blindsight”
Allowed by inferior colliculus???
From there, this sub-pathway goes on to the LGN
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Document Summary

Path that information takes from outside world through visual system. Right visual field to left eye connects to ipsi-lateral brain. Right visual field to right eye connects to contralateral brain. Left visual field to right eye connects to ipsi-lateral brain. Left visual field to left eye connects to contralateral brain. Only after reaches cortex, is visual field info combined via. Activates some of the same areas as actual visual perception. Seeing an elephant far away vs imagining an elephant far away. Magnocellular pathway - named after cells in retina. Large ganglions in rods and cones of periphery. Parvocellular pathway - named after cells in retina. Optic nerve (axons of ganglions) to lgn (lateral geniculate nucleus) of thalamus. Optic chiasm is where cross-over of optic nerves occur. Magnocellular pathways are layers 1 and 2. Layers also organized by which eye (l or r) is.

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