1
Q
how much of the brain is devoted to processing visual information
A
1/3
2
Q
what happens when visual information is in conflict with information from our other senses?
A
- bias trust towards vision
- i.e. in movies, the sound is coming from speakers but we attribute it to actor’s mouths on screen
3
Q
what is light
A
- form of electromagnetic radiation
- travels as a wave
4
Q
what impacts the colour we perceive light to be?
A
wavelength
5
Q
wht colours are the wavelengths?
A
- long: red
- short: violet
6
Q
shortest wavelength we can perceive with our eyes
A
360 nanometers (violet)
7
Q
longest wavelength we can perceive with our eyes
A
750 nanometers: red
8
Q
can diff species see diff wavelengths of light?
A
- yes
- bees can see shorter than the 360 nm in UV spectrum for flowers
- snakes can see longer than 750 nm in infrared spectrum to see body heat of prey in dark
9
Q
what do mammals see?
A
- only primates can see full range of colours as humans
- other mammals can only see in shades of grey
10
Q
how many cones do primates have for colour vision? how does this help us?
A
- three
- helps when foraging for ripe fruit in front of green bushes/trees (added contrast btwn objects n background)
11
Q
wavelength and frequency
A
- short wavelength = high frequency
- long wavelength = low frequency
- both impact colour perception
12
Q
amplitude
A
- height of wave peaks
- affects brightness perception
- greater amplitude = more light emitted = brighter/intense
13
Q
purity
A
- impacts saturation perception
- single wavelength = pure light
- natural light is usually a combination of many wavelengths and is desaturated
14
Q
start of the visual pathway
A
eye: gathering point for light waves to be captured
15
Q
what order of structures does light pass in the eye?
A
- curved cornea: begins focusing process
- pupil
- lens: final focusing of light
16
Q
cornea
A
transparent window at front of eye
17
Q
what is the eye covered with around the cornea?
A
- sclera
- tougher white membrane
18
Q
iris
A
- coloured part of eye
- controls size of pupil
- is a band of muscles controlled by brain
- if brain isn’t getting enough light, iris muscles will dilate into a larger opening
- if brain is getting to light, iris muscles will constrict into smaller opening
19
Q
pupil
A
round black window in centre of iris
20
Q
lens
A
- focuses light onto the retina at back of eye
- curvature causes image to land on retina upside down AND reverse from left to right
- flexible piece of tissue
- accommodation
21
Q
why don’t we see everything upside down and flipped?
A
brain activity
22
Q
accommodation
A
- change in shape of lens to focus on objects that vary in distance
- close objects = rounder lens
- further objects = elongated lens
23
Q
where does light go after passing the lens?
A
vitreous humor
24
Q
vitreous humor
A
- clear, jellylike substance
- comprises the main chamber inside the eyeball
25
where does light go after passing through chamber of vitreous humor?
retina
26
retina
- paper thin, neural tissue that lines the back of the eye
- made up of neurons arranged in three diff. layers
27
layers of the retina
layer at back: photoreceptors
- light sensitive, photoreceptors
- photoreceptors are cells in retina that translate physical stimulus of light into a neural signal
middle layer: bipolar cells
- send info to next layer
layer closest to light: ganglion cells
- collect info from larger segment of retina
28
why are the layers of the retina “inside out”?
- photoreceptors get nutrients fro layer of cells at back of eye called RPE (retinal pigment epithelium)
- need access to RPE to live
- two layers closest to light are transparent
29
two types of photoreceptors + how many there are
- rods: 125 million
- cones: 6 million
30
cones
- day vision
- sensation of colour
- good visual acuity
- concentrated towards fovea
31
fovea
- tiny spot in middle of retina that contains exclusively cones
- when we want to see something, we move our eyes so tht image falls directly onto fovea
32
rods
- operate at low light intensities
- night vision
- no colour information
- poor visual acuity
- concentrated in periphery (region just surrounding the fovea)
- good for peripheral vision
33
in a dimly lit environment, is it better to look directly at or to side of object?
- side of
- so that our rods are being used
- rods are not in the fovea, so we can’t look directly at object (otherwise, using cones)
34
where do photoreceptors send information to?
bipolar cells
35
bipolar cells
send info to ganglion cells
36
ganglion cells
- axons of ganglion cells all converge at optic disc
- from optic disc, they leave eye to join the optic nerve (which travels to the brain)
37
optic disc
- where ganglion axons converge
- exit hole in eye for ganglion axons
- has no photoreceptors at all
- makes up our blind spot
38
what causes our blind spot
optic disc
39
which cells in the retina allow area within a retina layer to communicate w/ each other?
- horizontal cells
- amacrine cells
40
horizontal and amacrine cells
allow info from adjacent photoreceptors to be combined
41
how many axons exist in the optic nerve? what does this mean?
- 1 million
- the over 160 million rods/cones must converge to travel along this
- thus, visual processing is done in the retina before signal is sent to brain
42
why does the fovea have more visual acuity?
- photoreceptor group for a ganglion cell may have just one cone
- thus, the ganglion cell represents a small area of what is being seen
- since each cone in the fovea has a direct link to brain, more detail is preserved
43
why is visual acuity lower for peripheral vision?
- often, input from many cones and rods is combined into one neural signal for one retinal ganglion cell
- groups get larger as we move to periphery of eye, leading to lower visual acuity
44
receptive field of a ganglion cell
the collection of rods and cones in the retina that affect the firing of a particular ganglion cell when stimulated
45
does the retina just take in information and pass it onto other areas for processing?
- no
- retina is where processing of light begins
psych 1xx3
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