perception 2

Question 1

what is visible light?

Answer 1

band of energy in electromagnetic spectrum

Question 2

what are the different wavelengths of light?

Answer 2

400-700nm

Question 3

what are the different wavelengths of light associated with?

Answer 3

different colour perceptions

Question 4

what does light consist of?

Answer 4

photons

Question 5

what is luminance?

Answer 5

number of photons in space, associated with brightness perception

Question 6

what is absorption?

Answer 6

photons collide with particles of matter

Question 7

what is reflection?

Answer 7

light strikes opaque surfaces

Question 8

what is transmission?

Answer 8

light passes through transparent matter

Question 9

what does the eye use to project an image onto the retina?

Answer 9

convex cornea and lens

Question 10

what do photoreceptors do?

Answer 10

transform light into an electrical potential

Question 11

how do light signals leave the eye?

Answer 11

flow through neurons to retinal ganglion cells
then out of eye via optic nerve

Question 12

where are rods located?

Answer 12

in the peripheral retina

Question 13

where are cones located?

Answer 13

centre of retina (fovea)

Question 14

which can operate in low light- rods or cones?

Answer 14

rods

Question 15

why are rods sensitive to light?

Answer 15

many rods join to one neurone, so many weak generator potentials combine to reach the threshold

Question 16

why are cones less sensitive to light?

Answer 16

one cone joins to one neurone, so it takes more light to reach the threshold and trigger an action potential

Question 17

why do rods have low visual acuity?

Answer 17

many rods join to the same neurone, so lights from two points close together can’t be told apart

Question 18

why do cones have high visual acuity?

Answer 18

one cone joins one neurone, so the brain receives separate action potentials for each form of light

Question 19

how many photopigments do cones have?

Answer 19

3

Question 20

what are the different photopigments in cones sensitive to?

Answer 20

short
medium
long
wavelengths of light

Question 21

what is the visual pathway from the retina to the brain?

Answer 21

retina
optic nerve
optic chiasm (optic nerves cross)
LGN
primary visual cortex (receives and integrates visual info)

Question 22

what is bottom up brightness perception?

Answer 22

responses to brightness are caused by processes within the retina

Question 23

what is top down brightness perception?

Answer 23

brain uses knowledge about how light interacts with objects to determine perceived brightness

Question 24

what is light/dark adaptation?

Answer 24

sensitivity of retina constantly adjusts to compensate for changes in luminance

increases when low, decreases when high

Question 25

what does light/dark adaptation mean the retina encodes?

Answer 25

contrast= ratio of object's luminance relative to the background luminance

Question 26

what is lateral inhibition?

Answer 26

information processing in retina retinal ganglion cells receive excitatory and inhibitory input from neighbouring photoreceptors

Question 27

what is the influence of lateral inhibition?

Answer 27

makes visual system sensitive to changes in luminance this helps detect the edges of objects affects perceived brightness

Question 28

what photopigment do rods contain?

Answer 28

rhodopsin

Question 29

which photopigments can cones contain?

Answer 29

S cones M cones L cones

Question 30

what are S cones?

Answer 30

blue cones, sensitive to short wavelengths

Question 31

what are M cones?

Answer 31

green cones, sensitive to middle wavelengths

Question 32

what are L cones?

Answer 32

red cones, sensitive to long wavelengths

Question 33

what are the three photopigments in cones known as?

Answer 33

trichromacy

Question 34

what is monochromacy?

Answer 34

individuals have 0/1 functioning cone types

Question 35

what is dichromacy?

Answer 35

individuals have 2 functioning cone types

Question 36

what is anomalous trichromacy?

Answer 36

individuals have a defect in one of three cone types

Question 37

what is colour opponency?

Answer 37

retinal ganglion cells receive excitatory or inhibitory input from different cone types =red/green and blue/yellow pathways demonstrated using negative afterimages

Question 38

what is colour perception?

Answer 38

top down tendency for the perceived colour of objects to remain the same, even if the lighting changes