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31 Cards in this Set
- Front
- Back
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What are the 5 central prjections of the optic nerve?
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1. SCN - super chiasmatic nucleus
2. Pretectal Nuclei 3. Superior Colliculus 4. Accessory optic nuclei 5. LGN - lateral geniculate nucleus |
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The right hemifield projects to which side of the brain?
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LEFT
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Which optic nerve fibers cross?
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The Nasal neurons
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Which optic nerve fibers do NOT cross?
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Temporal neurons because already carry information about opposite visual field
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How many layers does the Lateral Geniculate have?
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6
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How are the layers of the LGN sorted?
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According to the type of RGC (retinal ganglion cell) afferents making synapses in each one
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Are the eyes mixed are kept separated in the LGN?
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Kept separated
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Layers 1, 4, 6 correspond to what?
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Contralateral eye
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Layers 2, 3, 5 correspond to what?
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Ipsilateral eye
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Are midget and parasol RGC axons kept separate?
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YES
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Where do midget cells terminate?
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Parvocellular layers (hence the term P-cells)
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Where do parasol cells terminate?
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Magnocellular layers (hence the term M-cells)
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How are on/off center cells organized in PARVOCELLULAR layer?
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Kept separate
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What is the overall organization of the LGN?
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Retinotopic organization
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What is the organization of LGN in terms of space allocation?
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Much more space devoted to the fovea and central visual field than eccentric portions
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Where is the striate cortex (primary visual) located?
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Occipital lobe - upper/lower banks of calcarine fissue
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Upper visual fields are represented where?
Lower? |
Upper = lower bank of calcarine fissure
Lower = upper bank of calcarine fissure |
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Where is the fovea represented?
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Occipital pole
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What is the input layer to the primary visual cortex?
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IV
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Which layer changes from M cell format to something that is binocular, steroscopically, directional, and orientation selective?
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IVB
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What layer receives single M cells and has the same RF as M cells?
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IVCa
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How is IVB organized?
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With ON-center and OFF center inputs segregated in space
Gives ORIENTATION SELECTIVITY |
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What 3 items do cells in layer IVB encode?
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1. Presence of FEATURES in the visual scene
2. Distance away 3. Motion |
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Draw out overall M cell pathway
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3I-17
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Where do P cells terminate?
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IVC-beta
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IVC-beta then projects to where?
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Superficial layers of cortex (II and III)
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In the primary visual cortex, do M and P cells combine?
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NO, P and M systems remain largely separated
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What are ocular dominance columns?
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Stripes of neurons in the visual cortex that respond preferentially to one eye or the other
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Cytochrome oxidase blobs have what characteristics?
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Center-curround RFs
Color coded Part of the P pathway |
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Where are the cytochrome oxidase blobs located?
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Dead center in the ocular dominance columns
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What does lateral connectivity do to neurons with similiar RF's?
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Allows 2 cells to fire synchronously when the RF's have the same orientation, even when separated in the visual field
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