Sensation and Perception 2 Flashcards
retina
final stop for light in eye
light-senstivie area at back of eye containing three layers: ganglion cells, bipolar cells, and rods and cones
absorbs and processes light information
rods and cones
special receptor cells (photoreceptors)
respond to various wavelengths of light
receive photons of light and turn them into neural signals for brain, first to bipolar cells then ganglion cells
bipolar cells
interneurons
single dendrite at one end and single axon at other end
ganglion cells
axons of these form optic nerve
rods
100 mil concentrated in periphery black, white, and gray vision many connected to one bipolar cell so if one stimulated whole area send signals visual acuity (sharpness) low
cones
6 mil
receptors for visual acuity or ability to see fine detail
all over retina; concentrated at center where no rods exist
need light to function, work best in bright light
responsible for color vision because sense different wavelengths
fovea
center of retina
no rods
cones concentrated here
blind spot
place where there are no rods or cones
don’t see anything but brain fills in
optic disk
place where all axons of ganglion cells leave retina to become optic nerve
optic chiasm
point of crossover
info from left visual field goes to right visual cortex and vice versa
bc axons from temporal halves of each retina project to visual cortex on same side, axons from nasal halves cross over to other side
dark adaptation
occurs as eye recovers ability to see when going from brightly lit state to dark state
rods
brighter light = longer to adapt
older = takes longer
night blindness
person has difficulty seeing well enough to drive at night or get around in darkened room or house, because of age
vitamin A may help
light adaptation
going from darkened room to brightly lit one
cones have to adapt to increased level of light
quicker than rods adapt to darkness, few seconds at most
trichromatic “three colors” theory
young and helmholtz
proposed three types of cones: red cones, blue cones, and green cones
different shades of colors correspond to different amounts of light received by each of three cones
combination of X and X that determine color seen
cones
rate at which cones are firing
brown and wald
3 cones in retina, each sensitive to range of wavelengths and peak sensitivity that corresponds to 3 colors
short wavelength = blue violet
medium wavelength = green
long wavelength = green-yellow
afterimages
occur when visual sensation persists for brief time even after original stimulus is removed
opponent process theory
hiring
four primary colors: red, green, blue, and yellow
colors in pairs w/opponents (red v green, blue v yellow)
if one member of pair stimulated, other member inhibited and can’t work
which theory is right
both
trichromatic explains what happens with raw stimuli, actual detection of wavelengths of light
opponent process explains afterimages and other aspects of visual perception that occur after initial detection of light from environment
lateral geniculate nucleus
contains opponent process cells
part of pathway that visual info takes to occipital lobe
along with retinal cells, responsible for opponent processing of color vision and afterimage effect
color deficient vision
caused by defective cones in retina of eye
monochrome color blindness, dichromatic vision
monochrome color blindness
people either have no cones or cones that are not working at all
see world in shades of gray
dichromatic vision
one cone that doesn’t work properly, see world with combination of two cones/colors
red-green color deficient
lack of functioning red or green cones
confuses red and green
sees world in blues, yellow, and shades of gray
blue-yellow color deficiency
less common
see world in reds, green, and shades of gray
sex linked inheritance
color deficient vision is this
on X chromosome
more common in men
