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33 Cards in this Set

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