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33 Cards in this Set
- Front
- Back
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Daunting task that is required of the eye:
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To infer the attributes of objects and surfaces from reflected light that enters the eye.
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How is it that we can determine so many attributes from retinal signals when they are only signals of intensity of light detected by photoreceptors?
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There are hierarchical intervening stages of the info, processed in multiple parallel pathways.
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How does the HIERARCHICAL and PARALLEL nature of visual processing affect lesions?
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1. Lesions at higher levels will be more complex
2. Lesions can result in loss of some functions but spare others. |
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2 main components of higher visual processing:
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1. Recognition - What - 3D form/surface properties
2. Localization - Where - 3D spatial relationships and movement |
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Lesions in the temporal lobe affect what part of vision?
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Recognition of what you're seeing
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Lesions in the parietal lobe affect what part of vision?
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Localization of where what you're seeing is
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What are deficits in the parietal lobe affecting localization termed?
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Attentional neglect.
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Where do projections to these parietal and temporal lobe pathways come from?
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V1 primary visual cortex
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What do we call these parietal and temporal lobe areas?
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Extrastriate
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Where in the cortex will lesions affect the WHOLE visual pathway?
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In LGN, V1, or V2.
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Where do lesions start being able to cause different distinct deficits of components of vision?
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After V2; in V3, and byond.
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What are the 2 regions of the LGN that recieve visual input?
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-Magnocellular cells
-Parvocellular cells |
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Which cells in the LGN are bigger; m or P?
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M cells
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M cells recieve input from:
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Parasol ganglion cells
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P cells recieve input from:
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Midget ganglion cells
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Which cells in the ganglion cell layer have bigger receptive fields? Which are there more of?
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-Parasol cells have a bigger receptive field
-But Midget cells are 90% |
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What type of signal do Magnocellular neurons respond to what type of signal? Why?
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Transient signals of movement because that's what Parasol ganglion cells detect.
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Parvocellular neurons respond to what type of signal? Why?
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Sustained signals of color and high acuity because that's what Midget cells detect.
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How are neurons arranged in the V1 primary visual cortex?
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In orderly and distinct groups that SELECTIVELY PROJECT to higher cortex areas.
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How are Color selective cells arranged in V1?
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Into COLUMNS that are rich in CYTOCHROME OXIDASE (blobs)
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How are Orientation selective cells arranged?
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In a regular array around the color columns.
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What cortical lamainae contain cells selective for binocular disparity?
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Cortical laminae 3 and 4
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Where are motion selective cells in V1 cortex located?
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In layer 4
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How big are individual complete cortical hypercolumns?
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2x2x2 (in humans)
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so how many complete cortical hypercolumns are found in v1?
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hundreds
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So what types of visual information are processed in V1 and V2?
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ALL TYPES
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What is the result of a lesion of V1 or V2?
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Complete blindness within the retinotopically corresponding portion of the visual field.
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What is stereovision?
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Depth perception?
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What is the basis of depth perception?
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Retinal disparity
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What is the result of a lesion in the hMT (human middle temporal) area?
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Can't percieve motion
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Result of a v4/v8 lesion:
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Achromatopsia - can't see color
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result of a lesion in the FFA (fusiform face area):
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Prosopagnosia - can't recognize faces
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Result of lesion to the PVA (unknown parietal activity) area:
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Attentional neglect - don't see things on the right, but see them when moved into the left visual field.
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