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pyb204 perception and cognition > week 2: vision > Flashcards

week 2: vision Flashcards

1
Q

for an object to be visible it must:

A

emit or reflect light

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2
Q

what is light

A

one part of a continuum called electromagnetic radiation (EMR)

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3
Q

when is an emr generated

A

when an atom emits a particle called photon

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4
Q

what determines the emr wavelength

A

the energy of the wave length

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5
Q

how much light does the human eye detect

A

only able to detect light within a narrow range of wavelengths

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6
Q

what gives rise to the perception of different colours

A

different wavelengths within the range of visible wavelengths

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7
Q

what is saccades

A

the constant movement of the eyes

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8
Q

what happens if an image stays stabilised on the retina

A

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

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9
Q

what are ciliary muscles

A

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

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10
Q

if the ciliary muscle relaxes what happens

A

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

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11
Q

if the lens is round what is the focal point

A

the far is blurred and the near is focused

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12
Q

what does it mean to be far or short sighted

A

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

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13
Q

at what age does your eyes stop focusing

A

40

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14
Q

why do we have 2 eyes

A

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

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15
Q

what is stereovision good for

A

depth perception

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16
Q

what is motion paralex

A

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

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17
Q

what part of the eye contains the most photoreceptors

A

the fovea

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18
Q

types of photoreceptors

A

cones and rods

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19
Q

what are cones good for

A

colour and detail

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20
Q

when is cones most active

A

during daytime/in good light

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21
Q

why are photoreceptors facing away from the light is travelling

A

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.

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22
Q

what kills photorecepetors

A

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

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23
Q

How does the choroid layer work to protect photoreceptors

A

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

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24
Q

where are cones located

A

fovea and periphery

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25
Q

how many cone cells are there

A

6 million

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26
Q

what are rod cells

A

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

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27
Q

where are rods located

A

periphery

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28
Q

how many rods are there

A

120 mil

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29
Q

what happens to the cone cells in the dark

A

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

30
Q

what are the 2 visual systems

A

photopic
scotopic

31
Q

what is photopic vision

A

bright light vision via cones

32
Q

what is scotopic vision

A

dim light vision via rods
black and white or slighty green

33
Q

what did von Kries observe

A

that individuals without rods were night blind

34
Q

how are peoples vision who dont have cones

A

they are blind only during the day/ bright light

35
Q

what do receptor cells synapse with

A

bipolar cells

36
Q

what do bipolar cells synapse with

A

ganglion cells

37
Q

what do horizontal cells connect to

A

different receptors or different bipolar cells

38
Q

what do amacrine cells connect with

A

different bipolar or different ganglion cells

39
Q

what do the connecting cells allow

A

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

40
Q

what happens as we move deeper into the retina

A

convergence
- average of 126 receptors connect to 1 ganglion cell

41
Q

what does a ganglion cell do

A

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

42
Q

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

A

excitatory and inhibitory

43
Q

what is the first thing the photoreceptors identify

A

an edge

44
Q

what is an on centre off surround ganglion cell

A

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

45
Q

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

A

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

46
Q

what does the retinal ganglion cell act as

A

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)

47
Q

what are ganglion cells which exhibit centre-surround antagonism called

A

x cells or y cells

48
Q

what are the x and y cell visual channels called

A

parvocellular and magnocellular systems

49
Q

what is the magnocellular system

A

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

50
Q

what is the parvocellular system

A

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

51
Q

parvocellular system characteristics

A

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

52
Q

magnocellular characteristics

A

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

53
Q

what is the magnocellular good at

A

perceiving movement

54
Q

where is movement perceived best

A

in the peripheral

55
Q

what is the function of the parvocellular system

A

detail, space and colour

56
Q

what is the function of the magnocellular system

A

motion, depth and time

57
Q

passage of the visual signal

A

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

58
Q

where do the optic nerves cross over

A

the optic chiasm

59
Q

what is the purpose of the tectopulvinar pathway

A

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

60
Q

where are the tectopulvinar system n1 located

A

in the thalamic region called the tectum

61
Q

what do cells in the superior colliculi receive their input from

A

the magno retinal ganglion cells

62
Q

what does the tectopulivnar system receive

A

back projections from the cortex

63
Q

how are the tectopulvinar cells organised

A

in topograpgic maps

64
Q

what are the 2 pathways in the tectopulvinar system n2

A

focal system and ambient system

65
Q

what is the focal system for

A

recognition

66
Q

what is the ambient system for

A

localisation

67
Q

what happens if we have no LGN

A

unable to recognise patterns

68
Q

what happens if we have no superior colliculi

A

able to recognise patterns but not able to accurately approach them

69
Q

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

A

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

70
Q

what cells act as feature detectors

A

cortical cells

pyb204 perception and cognition (12 decks)

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