week 2: vision

Question 1

for an object to be visible it must:

Answer 1

emit or reflect light

Question 2

what is light

Answer 2

one part of a continuum called electromagnetic radiation (EMR)

Question 3

when is an emr generated

Answer 3

when an atom emits a particle called photon

Question 4

what determines the emr wavelength

Answer 4

the energy of the wave length

Question 5

how much light does the human eye detect

Answer 5

only able to detect light within a narrow range of wavelengths

Question 6

what gives rise to the perception of different colours

Answer 6

different wavelengths within the range of visible wavelengths

Question 7

what is saccades

Answer 7

the constant movement of the eyes

Question 8

what happens if an image stays stabilised on the retina

Answer 8

it disappears as the photoreceptors stop firing and the brain fills in the missing information

Question 9

what are ciliary muscles

Answer 9

muscles in the eye that control the shape of the lens to accomodate near or far targets

Question 10

if the ciliary muscle relaxes what happens

Answer 10

the lens bulges and therefore focuses on the far and blurs the near

Question 11

if the lens is round what is the focal point

Answer 11

the far is blurred and the near is focused

Question 12

what does it mean to be far or short sighted

Answer 12

the focal point doesnt land right at the retina where it is meant to land

Question 13

at what age does your eyes stop focusing

Answer 13

40

Question 14

why do we have 2 eyes

Answer 14

so we have a back up and to derive more information from the image/environment

Question 15

what is stereovision good for

Answer 15

depth perception

Question 16

what is motion paralex

Answer 16

the more an object moves when you move your head the closer the object is to you

Question 17

what part of the eye contains the most photoreceptors

Answer 17

the fovea

Question 18

types of photoreceptors

Answer 18

cones and rods

Question 19

what are cones good for

Answer 19

colour and detail

Question 20

when is cones most active

Answer 20

during daytime/in good light

Question 21

why are photoreceptors facing away from the light is travelling

Answer 21

Human vision was designed for use in poor lighting (scotopic/night vision). Therefore photoreceptors are extremely sensitive to light that light is toxic to photorecptors.

Question 22

what kills photorecepetors

Answer 22

too much light causes the photoreceptors to oversaturate and remove colour which bleaches the photoreceptors and causes them to be inaffective

Question 23

How does the choroid layer work to protect photoreceptors

Answer 23

the choroid layer absorbs most of the light and reflects a small amount of light back to the photoreceptors

Question 24

where are cones located

Answer 24

fovea and periphery

Question 25

how many cone cells are there

Answer 25

6 million

Question 26

what are rod cells

Answer 26

low detail and low light, good for scotopic/ night time vision

Question 27

where are rods located

Answer 27

periphery

Question 28

how many rods are there

Answer 28

120 mil

Question 29

what happens to the cone cells in the dark

Answer 29

the cones go to sleep and the rods come into focus which allow us to see in the dark

Question 30

what are the 2 visual systems

Answer 30

photopic scotopic

Question 31

what is photopic vision

Answer 31

bright light vision via cones

Question 32

what is scotopic vision

Answer 32

dim light vision via rods black and white or slighty green

Question 33

what did von Kries observe

Answer 33

that individuals without rods were night blind

Question 34

how are peoples vision who dont have cones

Answer 34

they are blind only during the day/ bright light

Question 35

what do receptor cells synapse with

Answer 35

bipolar cells

Question 36

what do bipolar cells synapse with

Answer 36

ganglion cells

Question 37

what do horizontal cells connect to

Answer 37

different receptors or different bipolar cells

Question 38

what do amacrine cells connect with

Answer 38

different bipolar or different ganglion cells

Question 39

what do the connecting cells allow

Answer 39

horizontal and amacrine cells allow events at one location to influence events at another

Question 40

what happens as we move deeper into the retina

Answer 40

convergence - average of 126 receptors connect to 1 ganglion cell

Question 41

what does a ganglion cell do

Answer 41

acts like a lens as it captures an image over an area of the retina - receptive field it can also enhance the image in its local area

Question 42

what type of connections do ganglion cells have within their receptive field

Answer 42

excitatory and inhibitory

Question 43

what is the first thing the photoreceptors identify

Answer 43

an edge

Question 44

what is an on centre off surround ganglion cell

Answer 44

a Ganglion cell that responds best when it receives stimulation in the centre of the visual field and gets suppressed when it receives light outside of the visual field

Question 45

what is an off centre on surround ganglion cell looking for, when does it function best

Answer 45

The cell is looking for a dark spot in a bright background. Functions best when the light is outside of the visual field

Question 46

what does the retinal ganglion cell act as

Answer 46

edge detectors integrate pattern of lightness over an area indicate whether that pattern of lightness within an area is different to that in an adjacent area (an edge)

Question 47

what are ganglion cells which exhibit centre-surround antagonism called

Answer 47

x cells or y cells

Question 48

what are the x and y cell visual channels called

Answer 48

parvocellular and magnocellular systems

Question 49

what is the magnocellular system

Answer 49

older system by passers the brain and goes straight to lower brain structure and sometimes directly to regions that enable us to respond to the info fast

Question 50

what is the parvocellular system

Answer 50

projects to the high cortical areas and tends to be used for information processing

Question 51

parvocellular system characteristics

Answer 51

small in size sustained response Receptive Field small x cells distributed in the foveal poor movement slow speed of nerves

Question 52

magnocellular characteristics

Answer 52

large in size transient response Receptive Field large y cells in the peripheral good movement fast nerve speed

Question 53

what is the magnocellular good at

Answer 53

perceiving movement

Question 54

where is movement perceived best

Answer 54

in the peripheral

Question 55

what is the function of the parvocellular system

Answer 55

detail, space and colour

Question 56

what is the function of the magnocellular system

Answer 56

motion, depth and time

Question 57

passage of the visual signal

Answer 57

information from the left visual fields of both eyes travels to the right side of the brain to be processed. Information from the right visual field of both eyes is processed in the left side of the brain

Question 58

where do the optic nerves cross over

Answer 58

the optic chiasm

Question 59

what is the purpose of the tectopulvinar pathway

Answer 59

the basic relay system that doesnt need to go through the brain. Used when you need a response really fast eg, ducking for safety

Question 60

where are the tectopulvinar system n1 located

Answer 60

in the thalamic region called the tectum

Question 61

what do cells in the superior colliculi receive their input from

Answer 61

the magno retinal ganglion cells

Question 62

what does the tectopulivnar system receive

Answer 62

back projections from the cortex

Question 63

how are the tectopulvinar cells organised

Answer 63

in topograpgic maps

Question 64

what are the 2 pathways in the tectopulvinar system n2

Answer 64

focal system and ambient system

Question 65

what is the focal system for

Answer 65

recognition

Question 66

what is the ambient system for

Answer 66

localisation

Question 67

what happens if we have no LGN

Answer 67

unable to recognise patterns

Question 68

what happens if we have no superior colliculi

Answer 68

able to recognise patterns but not able to accurately approach them

Question 69

what happens if you have damage to the focal system (blindsight)

Answer 69

can still react to stimuli eg. point to them but they cannot see them (cortically blind)

Question 70

what cells act as feature detectors

Answer 70

cortical cells