Vision Flashcards
sclera
the whites of the eyes - tough, opaque, fibrous, and for protection
cornea
clear, domed lens which accounts for ~80% of the eye’s focusing power
iris
the ring of colour around the pupil which controls the diameter of the pupil
lens
a flexible, curved structure which accounts for the remaining ~20% focusing power
accomodation
the lens’ shape adjusting to see nearer or farther
near accommodation
muscles flex, lens becomes rounder
far accommodation
muscles relax, lens flattens
hyperopia
farsightedness - light is focused behind retina
myopia
nearsightedness - light is focuses before retina
retina
thin, transparent sheet of tissue at the back of the eye that receives the image
rods
for scoptic (low light) vision, contains rhodopsin
cones
for photopic (high light) vision, contains idopsin, are chromatic
fovea
the centre of the retina (0°), consists solely of cones with a ring of rods around it (20°)
back layer
photoreceptors - rods and cones
middle layer
horizontal cells, amacrine cells, and bipolar cells - begin processing
top layer
ganglion cells, which relay the signal to the brain
parvocellular cells
p-cells, are smaller and convey details for perception of pattern, form, texture, depth, etc
magnocellular cells
m-cells, are larger and convey information about movement
optic disc
lacks photoreceptors, is where the axons of the ganglion cells exit the eye
centre-surround antagonism
centre of a ganglion receptive field responds to light, but the outer ring responds in the opposite way
binocular zone
where the visual fields overlap
monocular zone
what can only be seen by one of the eyes
nasal hemi-retina
the half of the retina closest to the nose
temporal hemi-retina
the half of the retina closest to the temples
optic nerve
the exiting ganglion axons
optic chiasm
where the optic nerves cross each other, the temporal information is sent to the opposite side of the brain
optic tract
the names of the nerve bundles once they pass the optic chiasm
pretectal midbrain
a destination of the optic tract, controls the pupil reflexes in response to light changes
retinohypothalamic fibers
a destination of the optic tract, regulates circadian rhythm
superior colliculus
a destination of the optic tract, controls saccadic (high velocity) eye movements and coordinates visual, auditory, and somatosensory information
lateral geniculate nucleus (LGN)
a destination of the optic tract in the midbrain thalamus, is a visual processing hub with six layers
LGN layers 1 and 2
processes m-cells
LGN layers 3 through 6
processes p-cells
striate cortex
the primary visual cortex (V1) and the second stop for visual information, contains simple, complex, and hyper complex cells
ocular dominance columns
respond to input from a single eye, neighbouring columns respond to inputs from the other
orientation columns
groups of cells with preferences towards certain orientations
exstriate cortex
the areas surrounding the striate cortex: V2, V3, V4, V5 (MT), and IT
feature detectors
another name for V1 cells due to their tendency to respond discriminately to features
dorsal pathway
to the parietal lobe - the “where” or spatial processing of visual stimuli, includes V3 and V5
V3
gets input fromV1 and V2 to process “global motion” in the visual field
V5
plays a role in our perception of motion, is also known as MT (middle temporal)
ventral pathway
to the temporal lobe - the “what” or identity processing of visual stimuli, includes V2, V4, and IT
V2
looks for properties such as orientation, spatial frequency, and colour
V4
responds to geometric shapes and colours
motion parallax
a monocular depth cue, uses the perceived speed of nearby and distant objects
optic flow
a monocular depth cue, uses the motion of the visual field due to your own movement through the environment
interposition
a monocular depth cue, uses the overlapping of objects to infer depth
linear perspective
a monocular depth cue, uses the sizes of distant and nearby objects to infer depth
aerial perspective
a monocular depth cue, the assumption that farther objects look hazier and bluer
shading
a monocular depth cue, infers depth via the shadows cast by the sun
stereopsis
a binocular depth cue, uses the differences in the images from each eye to infer depth
wavelength
hue
purity
saturation
amplitude
brightness
protanopia
loss or dysfunction of red cone
deuteranopia
loss or dysfunction of green cone
tritanopia
rare (not sex related), loss or dysfunction of blue cone
