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55 Cards in this Set
- Front
- Back
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Visual system requires roughly how much of the brain for visual capacity?
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1/3
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What is the problem of processing visual information?
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The forward problem of optics and the inverse problem of vision.
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Injury to back of the head (occipital lobe) might induce what?
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Visual disturbance or loss
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Pathway of visual tract.
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retina > optic nerve > optic chiasm > optic tract > lateral geniculate nucleus of thalamus > optic radiation to primary visual cortex
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How do human visual abilities differ from a camera?
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We record AND perceive
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Major targets of retinal ganglion cells.
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Retinal recipient nuclei
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90% of retinal ganglion cells terminate here.
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lGN
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Four locations other than LGN that retinal ganglion cells terminate.
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superior colliculus (5-7%), suprachiasmatic nucleus (circadian), pretectum (pupillary light reflex), and accessory optic system (stabilize one's gaze)
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Rapid, pointing eye movements moderated by tehh superior colliculus.
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saccades
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a. Pupillary light reflex circuit pathway.
b. Out of nearly a million ganglion cells, how many take this route on each side for the reflex? |
a. Photons reach retina > optic nerve > optic chiasm > pretectal olivary nucleus sends fibers to BOTH Edinger-Westphal nuclei > CN III > Ciliary ganglion > ciliary nerves > iris constrictor muscles
b. only a few thousand |
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Result of a lesion in the LGN > cortex. Can someone with a cortical lesion act on visual information?
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Complete blindness, but some reflexes can remain. Yes, they can act on visual information, but have no conscious awareness of it.
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Caused by lesions in retina to LGN to primary visual cortex system?
What about lesions in other parts of the cortex? |
Specific visual field defects.
Lesions in other parts of the cortex will cause more subtle visual defects. |
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Involves a very limited ability to perform visually guided tasks when there is destruction along the visual tract; in the apparent absence of conscious perception. Will respond to certain visual stimuli, but they claim to see nothing.
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Blindsight
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Lesions here will cause more subtle defects in person's ability to comprehend what they are looking at. Normal visual fields and acuity.
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Extrastriate cortex
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What is:
a. OS b. OD |
a. oculus sinistra (left eye)
b. oculus dextra (right eye) |
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Injury to right optic nerve results in what?
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OD blindness
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Lesion at optic chiasm leads to what?
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bitemporal hemianopia. Lateral half of vision in each eye is knocked out.
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Lesion to right optic tract will result in what?
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left homonymous hemianopia (left half of visual field knocked out in both eyes)
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Lesion to right Meyer's loop will result in what?
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Left superior quadrantanopia (superior lateral quadrant is knocked out equally in both eyes)
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Lesion to visual cortex will result in what?
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Left or right homonymous hemianopia with macular sparing.
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Three other names for primary visual cortex.
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Striate cortex, Area 17, Area V1
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Possible cause of lesions to visual system?
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pituitary tumors
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Mapping in visual cortex.
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Retinotopic map. Most of primary visual cortex is in the calcarine sulus, while the fovea is near the surface. Periphery is deeper.
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Attributed to the nose getting in the way of vision. Allows right eye to see further right than left eye can, and the inverse, etc.
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Right and left monocular crescents
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Most expensive effort in vision.
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analyzing and computing the image
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Part of the retina with a lot more detail than the periphery. Lot more information to analyze. Has a larger, strecthed out retinotopic map in cortex.
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Fovea
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Term describing larger representation of fovea than rest of eye on the visual cortex.
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Cortical magnification factor. Greatest amount of visual work occurs at 0 degrees.
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Names for LARGE and SMALL ganglion cells leaving the retina in a parallel pathway.
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MAGNO (large) and PARVO (small) ganglion cells.
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Ganglion cells not sensitive to color contrast, but have higher sensitivity to low contrast stimuli and temporal frequency, and lower sensitivity to spatial frequency (don't see fine detail.
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M cells
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Ganglion cells that respond to quickly moving objects (high temporal) and only see broad detail (low spatial).
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M cells
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Ganglion cells that have higher sensitivity to spatial frequency, and see color.
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P cells
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Ganglion cells that do not respond to quickly-moving stimuli, but process fine detail.
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P cells
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Ganglion cells that cross.
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1, 4, 6
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Ganglion cells that do not cross.
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2, 3, 5
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The two most ventral layers are what type of cell layers? The 4 most dorsal layers are what type of cell layers?
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M-cell layers; P-cell layers
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Is there binoculular computation between M & P cell layers bilaterally?
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NO
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Are most of the synapses on relay cells in the LGN from the retina?
What cells make local connections? LGN receives inputs from where else? |
No
Interneurons Brainstem, visual cortex (feedback), and peri-geniculate nucleus |
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Are there more interneurons than relay neurons?
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Yes
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Layer 4 of the six visual cortex layers.
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Stria of Gennari. Visual cortex has expanded 4th layer.
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LGN to Area V1 pathway.
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Thalamocortical or geniculostriate pathway.
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Deals with orientation of image, unlike ganglion cells of retina and LGN, which only differentiate between on/off center and surround.
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Area V1
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V1 cells that have discrete excitatory and inhibitory subregions like retinal ganglion cells, but RF subregions are not radially symmetric. Cell doesn't respond to uniform strip of light
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V1 simple cells
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V1 cells that do not have discrete excitatory or inhibitory regions. Selective for orientation. Gerneralize and can be more abstract.
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V1 complex cells
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If you had an ellipse and reversed the pink middle and gray sides, which V1 cells would recognize the difference?
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Simple cells
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While retina > LGN > V1 are obligatory for vision, what allows us to see well?
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Rest of the regions (V2)
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Dorsal stream pathway.
What type of cells does it involve and what do they tell us? |
V1 > V2 > MT > Post. parietal cortex
Magno/M cells. Tells us "where" an object is in space. |
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Ventral stream pathway.
What type of cells does it involve and what do they tell us? |
V1 > V4 > Inf. temporal cortex
Involves mostly parvo/P cells and tells us "what" we are seeing. |
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A lesion where will result in trouble with landmark discrimination in relation to other objects?
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posterior parietal lobe
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A lesion where will result in trouble telling different shapes apart?
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Inferior temporal cortex
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Cortical area closely associated to V1, higher level of abstraction as it fill in the details from contextual information.
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V2 (has both M and P cells) and is neither ventral nor dorsal.
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Cortical area that is more ventral stream and deals with complex color and form/shape (spirals) properties
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V4
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Cortical area (ventral stream), with high specificity in distinguishing between two faces. Can have large RF, but still high specificity.
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IT - inferior temporal cortex
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Loss of the ability to recognize faces with no corresponding loss of acuity or visual field defects.
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Prosopagnosia
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Cortical area inovlved in motion and perception of motion. Small component of the dorsal stream.
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MT (V5) Middle temporal cortex
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Loss of the ability to recognize faces with no corresponding loss of acuity or visual field defects.
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Prosopagnosia
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