Chapter 6 - Vision Flashcards
law of specific nerve energies
Muller’s idea that nerves specialized in one kind of energy (such as vision, audition, etc)
light from the left side of the world strikes which half of the retina?
the right (and vice versa)
what is the optic nerve made of?
ganglion cell axons
what causes the blind spot?
the point where the optic nerve leaves the eye has no visual receptors
what is the fovea specialized for?
acute, detailed vision
why is the fovea so good at detail?
each receptor cell connects to only one bipolar cell, which connects to only one ganglion cell, which has direct contact to the brain
Midget ganglion cells
the ganglion cells in the fovea. They are small and each responds to a single cone
rods
abundant in the periphery, respond to faint light
cones
abundant in and near the fovea, useful in bright light, essential for color vision
trichromatic theory
theory that color is perceived through the relative rates of response by three kinds of cones, each maximally sensitive to a different set of wavelengths
which cones are more abundant?
long and medium wavelength cones are far more abundant than short wavelength cones. this is why it’s harder to see blue
opponent process theory
the idea that we perceive color in terms of opposites. (a continuum from red to green, blue to yellow, and white to black)
color constancy
ability to recognize colors despite changes in lighting
retinex theory
the cortex compares information from various parts of the retina to determine the brightness and color for each area that we see
receptive field
area in visual space that excites or inhibits a cell in the visual system
three kinds of primate ganglion cells
parvocellular
magnocellular
koniocellular
parvocellular neurons
ganglion cells with small somas and small receptive fields, that are mostly in or around the fovea
magnocellular neurons
larger cell bodies and larger receptive fields, distributed evenly throughout the retina
koniocellular neurons
small somas and small receptive fields, distributed throughout the retina
what are parvocellular neurons good for?
detecting details. they respond to color too.
what are magnocellular neurons good for?
movement and large overall patterns
in humans, where do half of the ganglion axons cross contralaterally?
the optic chiasm
what is V1 (primary visual cortex, striate cortex) necessary for?
conscious visual perception
simple cell
cell in visual cortex that has a receptor field with fixed excitatory and inhibitory zones
complex cells
cells in the visual cortex that respond to a pattern or light in a particular orientation (ex: a vertical line). responds most strongly to moving stimulus
hypercomplex (end-stopped) cells
same as complex, but with strong inhibitory zone at one end
what do cells within a column of the visual cortex have in common?
they respond best to lines of the same orientation
retinal disparity
the difference between what the left and right eyes see
strabismus
lazy eye: a condition where the eyes don’t point in the same direction
astigmatism
a blurring of lines in one direction caused by asymmetric curvature of the eyes
ventral stream
area in the temporal cortex that is specialized for identifying and recognizing objects (the “what” pathway)
dorsal stream
area in parietal cortex that helps the motor system locate objects (the “where” pathway)
what do cells in the inferior temporal cortex respond to?
identifiable objects
visual agnosia
inability to recognize objects
propagnosia
inability to recognize faces
which brain areas are responsible for recognizing faces?
fusiform gyrus
anterior temproal cortex
prefrontal cortex
occipital cortex
which area responds more strongly to faces than anything else?
the fusiform gyrus
what do cells in V4 respond to?
perceived color of an object
Which two areas specialize in identifying motion?
V5 and area MST (medial superior temporal cortex)
what do cells in MT (V5) respond to?
when something moves at a particular speed in a particular direction (also images that imply movement)
what do cells in MST respond to?
complex stimuli such as expansion, contraction, and rotation of a visual scene
what do MST neurons enable you to do?
distinguish between the result of eye movement and the result of object movement
motion blindness
the ability to see objects, but impairment at seeing if they are moving
saccades
voluntary eye movements
