Lec. 11 (vision) Flashcards
how do we construct our representations of the external world?
sensation + perception
DETECT physical energy (a stimulus) from the environment and convert it into neural signals; processing external info inside our brain; raw data; BOTTOM-UP process
sensation
when we select, organize, and INTERPRET our sensations; adding meaning to our thoughts; separate objects and thoughs; TOP-DOWN process
perception
sensation is a ________ process and perception is a _________ process
bottom-up; top-down
T/F: sensation and perception occur at the same time in our brains
true
which process is determining the difference between the computer screen and the wall behind it?
perception
sensation (bottom-up processing): analysis of the stimulus begins with the ______ ______ and works up to the level of the brain and mind
sense receptors
perception (top-down processing): information processing guided by higher-level _______ _______ as we construct perceptions, drawing on our _______ + ________
mental process; experiences + expectations
during perception, we include ______ ______ into our thoughts
missing info
our sensory (bottom-up) and perceptual (top-down) processes work together to help us sort out _______ images
complex
light’s _____ ______ are perceived in specific ways (color and brightness)
physical properties
physical property of light that determines HUE (color) of light
wavelength
physical property of light that determines the INTENSITY (brightness) of light
amplitude
only 2 properties of light =
wavelength (color) + amplitude (brightness)
wavelength of light is measured in ______ or ______
meters or nanometers
short wavelength = which color?
violet
long wavelengths = which color?
red
short wavelengths that show violet are around ______ nm
400 nm
long wavelengths that show red are around ______ nm
700 nm
visible wavelength range =
400 - 750 nm
power or intensity of the radiant energy; the HEIGHT of the wave
amplitude
the higher the amplitude, the _____ the light
brighter
jelly-like, transparent fluid inside of the eyeball
vitreous humor
adjustable opening where light enters the eye; a HOLE
pupil
colored muscle surrounding the pupil, controls the aperture of the pupil; responds to light intensity or internal states; UNIQUE like fingerprints
iris
outer, protective covering of the eye
cornea
if you are RELAXED, your pupil _______
enlarges (opens up)
if you are CONCENTRATED, your pupil _______
gets smaller (clamps up)
if your pupil is unresponsive to light and does not change size, this can indicate what?
brain damage
pupil size is dependent on what 2 things?
amount of light + internal states/environment (ex: the task at hand)
what controls the size of the pupil?
iris
focuses light onto the retina; small muscles allow it to change shape to focus light – ACCOMODATIONS
lens
looking at something close and then far away; involuntary
accomodation
which part of the eye is responsible for accomodation?
the lens
the _______ of the lens is important for its function
flexibility
the flexibility of your lenses ______ with age and you can’t see close or far away as quickly (aka accommodation SLOWS down)
decreases
when lens get cloudy (cataracts), you can get surgery to replace them with a _______ version
plastic
a layer of photo-sensitive cells in the back surface of the eye ball
retina
the retina _______ photons into chemical changes that result in neural impules
transduces
converting light energy into chemical energy
transduction
a central area of the retina that contains only CONES
fovea
two main types of RECEPTORS/cells of the retina:
- cones
- rods
the rest of the retina besides the fovea contains ______
rods
the fovea is located where in the eye?
directly in the back of the eye, perpendicular
site of transduction =
retina
what causes your blind spot?
tail ends of neurons in retina going to optic nerve
vision process (4):
1) light reaches the rods and cones
2) chemical reactions activate the bipolar cell layer
3) bipolar cells activate the ganglion cell layer
4) the axons of the ganglion cells bunch up to from the optic nerve
3 layers of the retina:
- ganglion layer
- bipolar cell layer
- photoreceptor layer
only layer of the retina that is LIGHT SENSITIVE
photoreceptor layer
which layer of the retina has axons/tails that bunch up to create the optic nerve?
ganglion cell layer
highly aggregated (summarized) information from thousands of visual receptors are fed into the _______
ganglion
ganglion “sees” a small part of the world, known as their “__________ ________”
receptive field
types of activity of the ganglion (3):
- high
- medium
- low
type of ganglion activity: light on center and surround
medium
type of ganglion activity: light on center; dark on surround
high
type of ganglion activity: dark on BOTH center and surround
low
the ganglion has highly _______ vision
abstracted (sees brightness, edge, light, and dark)
carries signal from the eye to the brain
optic nerve
point where the optic nerve leaves the eye
blind spot
central point in the retina around which the eye’s cones cluster
fovea
which one do we have more of — rods or cones?
rods
number of rod receptors in our eyes =
~120 million
number of cones in our eyes =
~6 million
type of receptor: distributed ALL over the retina; detects black, white, grays
rods
type of receptor: concentrated on fovea; function in bright light conditions
cones
type of receptor: primarily responsible for PERIPHERAL vision and vision in the DARK
rods
type of receptor: primarily responsible for detection of DETAIL and COLOR
cones
T/F: you really don’t have color in your peripheral vision; top-down processing (perception) just fills it in
true
to find a DIM star, you should find it in your _______ vision
peripheral (disappears when you look right at it)
sensory switchboard; has left and right lateral geniculate nuclei (LGN)
thalamus
where L and R hemispheres of vision cross
optic chiasm
in journey from retina to brain, information is _______ and _____ many times, at all levels
processed and abstracted
nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement
feature detection
do we have brain tissue devoted to FASCIAL recognition?
yes
specific combinations of TEMPORAL lobe activity occur as people look at shoes, faces, chairs, and houses
shape detection
processing of several aspects of the stimulus simultaneously; brain divides a visual scene into subdivisions such as color, depth, form, movement, etc.
parallel processing
theories of COLOR vision (2):
1) tri-chromatic theory of color vision
2) opponent-process theory of color vision
theory of color vision: any color can be produced by mixing pure versions of BLUE, GREEN, and RED light in different amount
tri-chromatic theory of color vision
tri-chromatic theory of color vision says we have three types of ______
cones
3 sub-types of cones according to tri-chromatic theory of color vision:
- red cones
- blue cones
- green cones
genetic disorder in which people are blind to green or red colors; SUPPORTS the trichromatic theory
color blindness
fcolor blindness ______ the trichromatic theory
supports (ie. cant see red? red cones are working)
the trichromatic theory cannot explain some quirks of color vision, such as _________
afterimages
problem with trichromatic theory: red-green color blind people can see ______ – shouldn’t be possible bc it seems to be a pure color like R, G, and B
yellow
theory of color vision: visual elements sensitive to color are grouped into three pairs; the members of each pair OPPOSE/INHIBIT each other
opponent-process theory of color vision
3 pairs of opponent-process theory:
- red-green
- blue-yellow
- black-white
opponent-process theory of color vision explains the phenomenon of what 2 things?
- complimentary colors
- after images
according to the opponent-process theory of color vision, if red is stimulated/shown, your ability to see ______ is inhibited
green (when red is taken away, green shoots up in afterimage)
which color vision theory is correct?
both (color processing happens in stages/levels)
TWO color processing stages/levels
- photoreceptor level
- ganglion cell layer
color processing level: at this layer, you have 3 types of cones – TRICHROMATIC THEORY
photoreceptor layer
color processing level: at this layer, there are receptors paired among complimentary colors – OPPONENT-PROCESS THEORY
ganglion cell layer
which layer of the retina sends visual info to the occipital lobe/visual cortex
ganglion cell layer
the photoreceptor layer acts as “________” while the ganglion cell layer acts as the “_______”
employees; VP
