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31 Cards in this Set
- Front
- Back
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Map the passage of light from the cornea to the retina |
due to the refraction of light through the convex lens, the visual field is projected onto the retina UPSIDE DOWN & BACKWARDS
cornea > through pupil/iris > lens > posterior cavity > retina |
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Diagram the circuitry from the receptor cells in the retina to the visual cortex |
1. Photoreceptor cells
2. bipolar cells [primary sensory neurons]
3. Ganglion cells [2nd sensory neurons]
4. thalamus [3rd sensory neurons] |
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Diagnose a monocular vision loss |
a partial loss of vision or a blind spot in an otherwise normal visual field
lesion of the retina, fovea [scotoma] or Optic nerve [full monocular] |
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Causes of a monocular vision loss |
Glaucoma Optic neuritis Elevated intracranial pressure Optic glioma, schwannoma, meningioma trauma |
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Causes of Bitemporal hemianopia |
Lesion of the optic chiams [pituitary adenoma, meningioma] |
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Causes of Homonymous Hemianopia |
Includes any lesion retro to the chiasm Optic tract LGN Optic radiations Visual cortex |
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Causes of Quadrantanopia |
contralateral meyer's loop |
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Pathway of Visual Inputs from light to visual cortices |
1. Retina 2. Optic nerve 3. Optic chiams 4. Optic tract 5. Lateral Geniculate nuclei 6. Optic Radiations 7. Visual Cortices |
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Describe the physiological basis for color & form perception |
1. P-Cells [midget] 2. Parvocellular layers [Thalamus LGN] 3. Layer 4Cbeta to layer 2,3 blocks/interblobs [primary visual cortex] 4. Pale/thin stripe [visual association cortex] 5. occipitotemporal cortex
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Describe Blobs |
vertically oriented aggregates of neurons in layers II & III of the primary visual cortex that are sensitive to the color of vision. |
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Describe the Striate cortex |
the part of the occipital cortex that receives the fibers of the optic radiation from the lateral geniculate body and is the primary receptive area for vision |
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Describe the physiological basis for motion perception |
1. M-Cells [parasol] 2. Magnocellular layers [Thalamus LGN] 3. Layer 4Calpha to layer 4B [primary visual cortex] 4. thick stripe [visual association cortex] or parieto-occipital cortex [higher order visual association cortex] |
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Cells in the primary visual cortex project where? |
Visual association regions in the parieto-occipital & occipitotemporal cortices |
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Where do the dorsal pathways project? |
parieto-occipital association cortex |
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What do the dorsal pathways analyze? |
motion & spacial relationship between objects as well as between the body & visual stimuli |
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Where do the ventral pathways project? |
occipitotemporal association cortex |
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What do the ventral pathways analyze? |
form
with specific regions identifying color, faces, letters, & other visual stimuli |
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What is the "What" visual system? |
Ventral pathway
occipitotemporal association cortex |
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What is the "Where" visual system? |
Dorsal pathway
parieto-occipital association cortex |
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Describe Concept #1
Ganglion cells of the retina respond to what? |
Edges
they have center-surround receptive fields |
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Describe Concept #2
2 Types of Retinal Ganglion Cells |
Midget - P-cells Parasol - M-cells |
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Describe P-Cells |
- More sensitive to shape, detail & color
- respond to a single color with an on/off response
- Found in the fovea |
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Describe M-Cells |
- particularly involved in detecting movement in a stimulus
- receive input from many color cones
- do not have an on-off response to color |
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Describe Concept #3
Layers of the LGN |
- 2 ventral layers receive input from M-cells & project to layer 4Calpha of the primary visual cortex - 4 dorsal layers receive input from P-cells & project to layer 4Cb of the primary visual cortex - input from the .... keeps the two retinal visual fields separate * contralateral retina goes to layers 1,4 & 6. * Ipsilateral retina goes to layers 2,3 & 5 - cells in the LGN have center-surround receptive fields |
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Describe Concept #4
Retinotopical organization |
- Upper portion of the optic radiations project to the superior bank of the calcarine fissure to the primary visual cortex - inferior optic radiations terminate on the lower bank of the calcarine fissure - the primary visual cortex is retinotopically organized |
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Describe Concept #5
Hypercolumns |
The primary visual cortex has a complex organization based on hypercolumns composed of ocular dominance columns, orientation columns, blobs & interblobs |
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Describe optical dominance columns |
- columns that span the multiple cortical layers
- Laid out in a stripe pattern across the surface of the striate cortex.
- Stripes are perpendicular to the orientation columns |
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Describe orientation columns |
- organized region of neurons that are excited by visual line stimuli of varying angles. - located in the primary visual cortex & span multiple cortical layers - arranged in slabs that are perpendicular to the surface of the primary visual cortex |
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Describe Blobs |
- think color processing
- sections of the visual cortex where groups of neurons that are sensitive to color assemble in cylindrical shapes |
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Describe Interblobs |
- think shape
- areas between blobs which receive the same input but are sensitive to orientation instead of color |
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Describe the three parallel channels that carry the input into the primary cortex |
M-cells to cells in layer 4 of the cortex that detect orientation & motion
P-cells to interblobs layers 2,3 of the primary visual cortex to detect shape
P-cells to blobs in layer 2,3 of the primary visual cortex to detect color |
