Chapter 10: Vision and Visual Perception Flashcards
How is light described as?
wavelengths
What are visible light ranges?
~300 to 800 nm
How many light receptors does the eye contain?
126 million
What is the visible light spectrum?
The adequate stimulus of light that makes up 1/70th of the electromagnetic spectrum
How does light travel?
Through oscillating waves similar to sound
What is the unit of measurement of light?
a nanometer
Does the wavelength of light determine what color we see?
yes
Where are the rods and cones found?
in the back of the retina
What are the photoreceptors of light?
The rods and cones
What does photopigment react with?
light
Where is rhodopsin found?
in the rods in the periphery of the retina
Where is iodopsin found?
in the cones, mostly fovea and surrounding area
What does iodopsin lead to?
a neural impulse
What is the function of rhodopsin?
Cannot distinguish color, is poor in detail, and is poor or not at all function in bright light. However, it is good for dim light.
What is the receptive field of rhodopsin?
Contributes to light sensitivity and is large due to convergence of ganglion cells
What is the function of iodopsin?
Distinguishes color, detail is good, and is good in bright light but not in dim light
What is there more of in the retina?
Rods
What is there more of in the fovea?
Cones
What is the order after light hits?
rods/cones>bipolar cell>ganglion cells
What is the function of the fovea?
Differentiate among different wavelengths of light like red, green, and blue
What is fovea known for?
the area for greatest visual acuity
What is the receptive field?
The area in the retina from which ganglion cells receive input
What is the visual field?
The part of the environment that is being registered in the retina
What is visual acuity?
the ability to distinguish details
What are amacrine and horizontal cells responsible for?
Connecting to ganglion cells to provide the ability to distinguish details in visual acuity
The receptive field of cones are?
small
The receptive fields for rods are?
large
Visual acuity is the greatest in?
The fovea
Where do neurons go when the rods and cones fire?
The optic nerve through the blind spot
What is the receptive field of iodopsin?
Small, with few cones converging into one single ganglion cell that contributes to detail vision
What is the optic chiasm?
a part of the brain where the optic nerves cross
What is the retinal disparity?
A cue in order to perceive how far something is
How is blindness caused?
Deterioration of visual receptor but neural structures are intact
Can sight be restored?
Yes, through replacing receptors with an artificial retina
What is the trichromatic theory?
The primary colors are red, green, and blue they can detect every color
Who introduced trichromatic theory?
Young-Helmholtz
What is opponent process theory?
The ability to process colors is controlled by receptors with opposing actions such red-green, blue-yellow, and black-white. This theory explains the color yellow but is not backed up by physiological studies
Who introduced the opponent processing theory?
Hering
What is the combined theory?
We only perceive three colors which are red, blue, and green which can allow the eye to see every color in the visible light spectrum
Who introduced the combined theory?
Hurvich and Jameson
What is the cause of color blindness?
Defects in the cone system
What is form vision?
the detection of an object’s boundaries and features
Cells that activate when light hits the center, but turn off when light hits the periphery are called?
on center, off surround
What is Hubel and Wiesel’s theory?
receptive fields are not circular as they are in the LGN and instead there is simple and complex cells
What does the nervous system use to exaggerate brightness and contrast the edge of an object?
lateral inhibition
What is the function of simple cells?
cells that respond to edges and gratings
How is the visual cortex organized?
retinotopic where it hits in the retina is where it hits in the visual cortex but does not explain form vision
What is the function of complex cells?
Getting input from the simple cells and detects where something starts/ends and may know texture
What is spatial frequency theory?
different cells have different sensitivities and detect edges and graduation changes
What is modular processing?
Brain functions are in separate locations
What is hierarchical processing?
information is processed by ascending different levels in the nervous system
What is distributed processing?
process occurs across a wide area of the brain
What is the parvocellular system?
ganglion cells are located in the fovea, are small and discriminate fine detail and color
What is the magnocellular system?
ganglion cells are the in the periphery, large, fast on-fast-off, and brightness contrast and movement
What is the ventral system in the visual system?
process what something is (parvocellular)
What is the dorsal system in the visual system?
process where something is (magnocellular)
What happens when there is damage to the ventral system?
you can see, reach for, walk around objects but can identify them
What happens if there is damage to the dorsal stream?
you can identify objects but have trouble looking at, reaching for, and grasping objects
What is the dorsal and ventral system managed by?
The prefrontal cortex where it manages information like the body and objects in memory and plans movement
What are the vision systems used in the ventral system?
V1-V2 into V4 for color then the inferior temporal cortex for object recognition
What are the vision systems used in the dorsal system?
V1 for orientation, movement, and retinal disparity, then V2 and V5 for movement then the posterior parietal cortex
What is the function of the inferior temporal area?
object recognition like geometric figures, houses, hands, faces
What is object agnosia?
the impaired ability to recognize objects visually
What is prosopagnosia?
the impaired ability to visually recognize familiar faces
Is there a genetic link to prosopagnosia?
Yes, with deficits in frontal and temporal lobes on small number of cases
What is the damage of blindsight?
Damage to V1 that causes cortical blindness where individuals can react unconsciously without seeing anything
What is color agnosia?
the loss ability to perceive colors
What is movement agnosia?
the inability to perceive movement
What is fusiform face area?
a region of the fusiform gyrus critical for face recognition
What is visual word form area?
the inferior temporal cortex that responds to whole written words