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PSY219 NEURO > Vision > Flashcards

Vision Flashcards

1
Q

what is feature detection

A

sensory neurons detect colour/edges/lines

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2
Q

what is the role of the iris

A

regulate amount of light reaching retina

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3
Q

what is the role of pupil size

A

regulate sensitivity and acuity

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4
Q

what happens when pupils constrict

A

reduced light - increased sensitivity = sharp and great depth

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5
Q

what happens when pupils dilate

A

more light enter eye - sacrifice depth and acuity

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6
Q

what happens when more light enters the eye

A

image is more blurry and less acuity

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7
Q

what is the role of the cornea

A

help focus incoming light

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8
Q

what % is the cornea of the eye focusing power

A

75%

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9
Q

what is the lens help in place by

A

ligaments called zonules

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10
Q

what is the role of the lens

A

bends light to change focal distance

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11
Q

what is the process called to bend light to change focal distance

A

accomodation

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12
Q

what is the effect of a flatter lens

A

thinner = increased focal distance for distance objects

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13
Q

what is the effect of a rounder/thicker lens

A

bends light to reduce focus distance - short distance for sharper objects

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14
Q

what is retinography

A

imaging process of a retina

used by opticians

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15
Q

define transduction

A

light into neural code

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16
Q

what is the centre of the retina

A

macula

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17
Q

state characteristics of the macula

A

contains fovea

high concentration of photoreceptor cells

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18
Q

what effect occurs on the macula as age increases

A

macula degenerates - loss of central vision

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19
Q

what is the role of the fovea

A

site of sharpest vision

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20
Q

why does the fovea have sharp vision

A

contains lots of photoreceptor cells

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21
Q

what is the role of photoreceptor cells

A

convert light to neural signals

process of transduction

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22
Q

what is another name of the blind spot

A

optic disk

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23
Q

what is surface interpolation

A

perceived surface and fill in gaps of blind spot

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24
Q

what is sclera and its function

A

white of eye

protective tissue layer

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25
Q

what percentage of nerve fibres make up the fovea

A

50%

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26
Q

which region of the eye is densely packed with cones

A

fovea

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27
Q

what is the function of the blood vessels at the side of the fovea

A

reduce distortion of light

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28
Q

why is light distorted when it enters the human eye

A

human retina is inside out hence why black spots occur

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29
Q

is light distored in octupus

A

no because their retina is the right way round

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30
Q

what is choroid and its function

A

tissue between retina and sclera

provides oxygen and glucose to retina cells

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31
Q

what is the reflective tissue in nocturnal animals

A

tapetum lucidum

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32
Q

why does red eye occur from camera flash

A

flash reflected from blood in choroid

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33
Q

how is a blind spot filled

A

info from receptor is used to fill gap from blind spot

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34
Q

state 3 layers which compose the retina

A

photoreceptors
bipolar cells
retinal ganglion cells

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35
Q

state the two types of photoreceptors

A

rods and cones

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36
Q

why do stars seem to disappear at night

A

few roads in the fovea

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37
Q

state the follow characteristics of rods

  1. lighting
  2. type of vision
  3. level of convergence, sensitivity and acuity
A 
rods = scotopic 
operate in dim lighting 
peripheral vision 
high levels of convergence 
poor acuity 
high sensitivity
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38
Q

what is the term used to describe people with 3 cones

A

trichomats

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39
Q

state the following characteristics of cones

A 
cones= phototopic 
operate best in good lighting
central vision 
poor sensitivity 
low convergence 
high acuity
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40
Q

state the 3 types of cones

A

red
blue
green

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41
Q

define phototopic and which type of photoreceptor it links to

A

phototopic = vision in daylight or bright light

CONES

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42
Q

Define scotopic and which type of photo receptor it links to

A

scotopic = vision in dim light

RODS

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43
Q

what effect does more photoreceptors have on colour

A

more photoreceptors means better colour resulting power

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44
Q

which type of lighting is rhodosin active in

A

bright lihght

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45
Q

what effect does active rhodosin have

A
  1. cyclic GMP broken down
  2. sodium channel close
  3. cell becomes hyper polarised
  4. glutatmate release decreases
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46
Q

what effect occurs when rhodosin is not active in the dark

A
  1. sodium channels open
  2. cell becomes depolarised
  3. number of rods increase
  4. glutamate release increases
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47
Q

define deuteranamoly

A

partial loss of green colour vision

becomes harder to distinguish between red and green

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48
Q

what percentage of men and women experience colour blindness

A

.5% women

8% men

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49
Q

define colour blindness

A

altered sensitivity in cones or absence of cones

50
Q

what is the function of bipolar cells

A

process input from photoreceptor cells

51
Q

what do interneurons aid bipolar cells to do

A

allows low level signal processing of input from the photoreceptors

52
Q

describe the process of input and output of info in vision

A

input to photoreceptors
bipolar cells
retinal ganglion cells
output

53
Q

what is the function of ganglion retinal cells

A

facilitate detection of edges of images

54
Q

what cells are retinal ganglion cells linked up to

A

bipolar cells

55
Q

what is the basis for edge detection in retinal ganglion cells

A

maximise contrast to detect edges

56
Q

what colour does a single photoreceptor detect

A

greyscale

57
Q

what can 2-3 photoreceptors do

A

detect the difference between wavelength and intensity

58
Q

where was lateral inhibition first observed

A

horse shoe crab

59
Q

what is the ommatidia

A

large visual receptors

60
Q

define lateral inhibition

A

lateral inhibition is the capacity of an excited neuron to reduce the activity of its neighbors

61
Q

what effect does lateral inhibition cause in mach bands

A

causes contrast enhancement

62
Q

what is the link between light and firing intensity

A

amount of firing is proportional to light intensity

63
Q

what effect do sideways projections have as a result of lateral inhibition

A

inhibit activity of neighbour

64
Q

what is the hermann grid

A

white spots of light appear when not looking at target zone

65
Q

what causes the effects of the hermann grid

A

lateral inhibition

66
Q

why do the white squares appear in the hermann grid illusion

A

white squares appear at intersection when foveated

surrounded by more active receptor fields

67
Q

what is the process that occurs when eyes foveate

A
  1. light intensity projected to photoreceptors

2. retinal ganglion cells pass info on to form output

68
Q

what do horizontal cells do?

A

inhibit other cells when activated

69
Q

where are on centre cells responsive to light

A

centre of receptive field

70
Q

in on centre cells what would happen to firing in periphery field

A

firing in periphery field would be off

no light in periphery field

71
Q

where are off centre cells response to light

A

periphery receptive field

72
Q

what is the function of off centre cells

A

respond with inhibition

73
Q

how do off centre cells maximise contrast

A

maximise firing between centre and periphery field

centre surround difference

74
Q

what occurs to neighbours which experience high levels of inhibition

A

lower levels of firing due to inhibition from neighbours

75
Q

define receptive field

A

area of visual field where the visual stimulus can influence firing of neuron

76
Q

what kind of influences can the receptive field have on firing of the neuron

A

increase or decrease firing rate

77
Q

what did hubel and wiesel measure

A

3 layers of the retina geniculate striate pathway

78
Q

what are the 2 categories of neurons in the receptive field

A

simple cells and complex cells

79
Q

state characteristics of complex cells in the receptive field

A
  1. role in depth perception
  2. rectangualr receptive field
  3. binocular
80
Q

what do complex and simple cells respond best to

A

responsive best to straight line stimuli

81
Q

what type of receptors do simple cells have

A

antagonistic on and off receptors

82
Q

what type of organisation is the primary visual cortex composed of

A

corticol organisation made up of functional vertical columns

83
Q

what is needed for scene analysis

A

higher receptive field properties

84
Q

what is the perceptual binding problem

A

different stimuli are processed in different corticol areas

85
Q

what does V2 process

A

shape characteristic

86
Q

what is the function of V3

A

motion and depth perception

87
Q

what is the function of V4

A

colour and form perception

88
Q

what is the function of v5

A

motion perception

89
Q

where does info in the dorsal stream travel to

A

parietal lobe

90
Q

what type of info travels in the dorsal stream

A

process spatial locations

91
Q

what type of info and where does the info travel in the ventral system

A

object identity and scene analysis info travel to temporal lobe

92
Q

define visual agnosia

A

able to see object but can’t define or recognise it

93
Q

what is prosopagnosia

A

can’t recognise faces

94
Q

which brain region is damaged in prosopagnosia

A

fusiform face area

95
Q

what is visual neglect

A

people unaware of existence of part of their visual field

96
Q

define blindsight

A

person is conciously blind but retain visual ability or awareness

97
Q

what is meant by columnar organisation in vision

A

neural signals flow from simple to complex receptive fields

specific hierachy

98
Q

what is the horizontal electrode track

A

orientation of neurons at tip - shift systematically

99
Q

what vision function is the horizontal electrode track linked with

A

spatial location of receptive field

100
Q

which type of track are V1 neurons linked with

A

vertical electrode track

101
Q

where is the vertical electrode track grouped in

A

functional vertical columns

102
Q

define vergence

A

movement of image further away or closer to eyes

103
Q

what are projections to brain stem nuclei responsible for

A

responsible for visual reflexes eg. accomodation, vergence and pupil control

104
Q

where does the left visual field project to

A

right visual cortex

105
Q

where does the retino tectal pathway project to and what does it control

A

project to superior colliculus to orientate head and eyes

106
Q

what is another name for the superior colliculus

A

optic tectum

107
Q

what are the neurons in the superior colliculus sensitive to

A

luminate change

108
Q

what is the role of the retino-geniculate pathway

A

provide input to identify objects and scene analysis

109
Q

what are parvocellular cells and what are their function

A

small cell bodies

responsive to colour and stationary objects

110
Q

what are magnocellular cells and what is their role

A

large cell bodies

responsive to luminate change - on off movement

111
Q

which photoreceptor provide input for M and P cells

A 
cones = input for P cells 
rods = input for M cells
112
Q

what is the role of the lateral geniculate nucleus

A

thalamic relay for M and P channels

113
Q

what is retinotopic mapping proportional with

A

activity in the retina

114
Q

what is the activity in the retina disporportional to

A

disproportional to activity in visual cortex

115
Q

what does the right visual field project to

A

left primary cortex

116
Q

what does contralateral projections mean

A

projections from left visual field would go to right cortex

117
Q

what type of projections does the temporal hemiretina have

A

one way = ipsilateral

118
Q

what type of projections does the nasal hemiretina have

A

contralateral

119
Q

where does info that is projected contralaterally seperate

A

optic chiasm to superior colliculus and visual cortex

120
Q

state the key findings of hubel and wiesel

A
  1. receptive field is smaller in fovea than periphery
  2. receptive field has both excitory and inhibitory area
  3. receptive field is circular and monocular

PSY219 NEURO (14 decks)

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