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Neuroscience > Vision > Flashcards

Vision Flashcards

1
Q

Scotopic vision lacks both the ____ and _____ of photopic vision

A

Detail

Colour

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2
Q

Which out of photopic and scotopic vision has the greatest colour and detail?

A

Photopic

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3
Q

Two key properties of sensory systems

A

Feature detection

Adaptation

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4
Q

The transformation of electromagnetic radiation to neural impulses is known as

A

Transduction

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5
Q

What is transduction in relation to vision?

A

Electromagnetic radiation (light) –> neural impulses

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6
Q

The electromagnetic spectrum is made up of

A

Wavelengths visible to humans

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7
Q

Transduction, generally speaking, is

A

Conversion of one form of energy to another

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8
Q

Iris

A

Contractile tissue that regulates light input

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9
Q

How does the iris adjust light input?

A

By adjusting pupil size

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10
Q

What is pupillary light reflex?

A

Pupillary contraction/dilation controlled by light entering the eye

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11
Q

What does the iris muscle/pupil do in darkness?

A

Iris relaxes

Pupil delates

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12
Q

If the pupil dilates, does more or less light enter the eye?

A

More

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13
Q

Iris muscle relaxes & pupil dilates

Sensitivity – >

Acuity –>

A

Improves

Decreases

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14
Q

If the pupil gets smaller, ______ light enters the eye

A

Less

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15
Q

Iris muscle constricts and pupil gets smaller

Sharpness –>

Acuity –>

A

Improves

Improves

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16
Q

Tradeoff between _____ and ______

A

Acuity

Sensitive

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17
Q

Light

In darkness, each point projects to a larger area. These areas…

A

Overlap

Create blurring

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18
Q

Light

In lightness, less light is able to enter the eye. Each point projects to…

A

A smaller and more discrete area

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19
Q

Light

In lightness, less light is able to enter the eye. Each point projects to a smaller area. As a result,

A

There is less blurring

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20
Q

Where is the cornea situated?

A

Front of the eye

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21
Q

What does the cornea do?

A

Focuses incoming light

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22
Q

Where is the lens found?

A

Behind the pupil

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23
Q

Behind each pupil is a lens, which focuses incoming light on the….

A

Retina

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24
Q

Each lens is held in place by suspensory ligaments called

A

Zonules

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25
Q

The lens can change shape to change the focal distance of the eye, a process called

A

Accommodation

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26
Q

Accommodation is

A

Where the lens changes shape

Changes focal distance

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27
Q

Focusing

When we direct our gaze at something near, the tension

A

Holding each lens in place is adjusted by ciliary muscles

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28
Q

Focusing

If the lens is rounder, it reduces the….and creates a….

A

Focal distance

Sharper image

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29
Q

Focusing

What does the lens look like if focal distance is reduced and the image is sharper?

A

Rounder

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30
Q

Focusing

What does the lens look like at its weakest/thinnest?

A

Flatter

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31
Q

Focusing

What does the lens look like when focal distance is INCREASED to create a sharper image for distant objects?

A

Flatter

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32
Q

The retina contains a layer of….

A

Photoreceptive cells

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33
Q

The photoreceptive cells of the retina convert light into

A

Neural signals

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34
Q

What is found at the centre of the retina?

A

Macula

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35
Q

In the macula, there is a high concentration of….

A

Photoreceptor cells

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36
Q

What is the site of our sharpest vision?

A

Fovea

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37
Q

What is found at the centre of the MACULA?

A

Fovea

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38
Q

Age-related macular degeneration is the loss of

A

Central vision

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39
Q

Where is the highest concentration of photoreceptor cells found?

A

Macula

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40
Q

When you fixate on something, you are positioning it on the..

A

Fovea

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41
Q

Fovea

Rods/cones

A

Cones

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42
Q

Fovea

What is found on the fovea?

A

High density of cones

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43
Q

Fovea

How is distortion minimised?

A

Blood vessels/other cells displaced to the side

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44
Q

Why is it difficult to see things when you focus on them in darkness?

A

Fovea –> responsible for focusing

Only cones on the fovea

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45
Q

The blind spot is a…

A

Gap in the receptor layer

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46
Q

Blind spot

To minimise this problem, the brain uses…

A

Completion

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47
Q

What is completion?

A

Information provided by the receptors around the blindspot are used to fill the gap

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48
Q

Instead of extracting all visual information, the visual system extracts….

A

Key information, e.g. edges/location

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49
Q

What is the sclera

A

White layer of eye

Tough/protective

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50
Q

What is the choroid (3)

A

Layer of tissue between retina/sclera

Contains many blood vessels

Provides oxygen/glucose to retina

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51
Q

When we get ‘red eye’ in pictures, what is it?

A

Flash reflected off blood in choroid

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52
Q

Why is the eye anatomy of vertebrates inverted?

A

Space saving solution

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53
Q

Three main layers of cells in the retina

A

Photoreceptors
Bipolar cells
Retinal ganglion cells

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54
Q

Two types of photoreceptors in the retina

A

Rods

Cones

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55
Q

Species active in the day tend to have

A

Cone-only retinas

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56
Q

Species active only at night tend to have

A

Rod-only retinas

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57
Q

Species tend to have differing rod/cone levels according to when they are most active. From this observation emerged…

A

Duplexity theory

58
Q

Rods are responsible for _____ vision

A

Scotopic

59
Q

Cones are responsible for ______ vision

A

Photopic

60
Q

Rods operate in ____ lighting

A

Low

61
Q

High convergence of rods, which means…

A

Poor acuity

Good sensitivity

62
Q

Theres only one type of rod –>

A

Monochromatic

63
Q

Darkness –> rhodopsin inactive –> (3)

A
  1. Na+ channels open
  2. Rod depolarised
  3. Release glutamate
64
Q

Lightness –> rhodopsin active –> (4)

A
  1. Na+ channels close
  2. Rod hyperpolarised
  3. No glutamate released
  4. Bipolar cell depolarised
65
Q

Blue cones –> ___ wavelength

A

Short

66
Q

Red cones –> _____ wavelength

A

Long

67
Q

A SINGLE photoreceptor provides only ______ information

A

Greyscale

68
Q

2 photoreceptors allow you to

A

Distinguish wavelength from intensity

69
Q

COLOUR is encoded by differential…

A

Activation of 2 or more photoreceptors

70
Q

Most people are trichomats, having

A

3 types of cone

71
Q

__% of men have colour vision deficiency

A

8%

72
Q

In most cases of colour blindness, it leads to….(2)

A

Altered sensitivity in one of the cones, or absence

73
Q

Majority of cones are crammed into the

A

Fovea

74
Q

Fovea

Full of rods/cones

A

Cones

75
Q

How many fixations are made by the eye per second?

A

3

76
Q

3 fixations are made by the eye per second. The visual system then…

A

Integrates this information to produce wide-angled, high acuity, coloured perception

77
Q

Bipolar cells process

A

Input from the photoreceptors

78
Q

What is the output of bipolar cells?

A

Retinal ganglion cells

79
Q

Bipolar cells allow _____ signal processing to occur in the retina

A

Low-level

80
Q

Bipolar cells allow low-level signal processing to occur, aided by

A

The interneurons

81
Q

Photoreceptors converge via ______ onto retinal ganglion cells

A

Bipolar cells

82
Q

Few-to-one convergence for _____

A

Cones

83
Q

Many-to-one convergence for ______

A

Rods

84
Q

Few-to-one convergence for cones, which maintains

A

Excellent resolution

85
Q

MACH bands illusions are mediated by

A

Horizontal cells

86
Q

Mach bands

The apparent change in lightness between bands is an illusion called

A

Lateral inhibition

87
Q

Two properties of light

A

Wavelength (colour)

Intensity (brightness)

88
Q

Binocular disparity is the

A

Difference in position of the same image on the two retinas

89
Q

Binocular disparity is greater for

A

Close objects

90
Q

Binocular disparity is least for

A

Distant objects

91
Q

For a bundle of retinal ganglion cell axons to leave the eye, there must be a gap in the receptor layer –>

A

Blind spot

92
Q

2 problems with an ‘inside out’ retina?

A

Distorted image

Blindspot

93
Q

A problem with the inside-out retina is that the image is distorted. Which part of the eye corrects this?

A

Fovea

94
Q

What is the Purkinje effect?

A

Visual effect –> see more blue colours in darkness

95
Q

Humans have a photooptic spectral sensitivity curve and

A

A scotopic spectral sensitivity curve

96
Q

The reason our vision doesn’t vanish every time we blink?

A

Temporal intergration

97
Q

“Small jerky eye movements or flicks”

A

Saccades

98
Q

Saccades are critical for vision function because

A

The image will fade otherwise

99
Q

Breakthrough in visual transduction came with the discovery of

A

Rhodopsin (red pigment that absorbs light, extracted from rods)

100
Q

What happened to rhodopsin when it was exposed to intense light?

A

Bleached and lost ability to absorb light

101
Q

When was Rhodopsins ability regained?

A

Darkness

102
Q

What protein is the first step in rod-mediated vision?

A

Rhodopsin

103
Q

The absorption of rhodopsin is related to the ability

A

To view different light wavelengths

104
Q

Having subjects judge the relative brightness of different wavelengths is a way of measuring

A

Scotopic spectral sensitivity

105
Q

Most informative feature of any visual display?

A

Edges

106
Q

5 step process of transduction?

A

Light –> Photopigment –> Bipolar –> Ganglion –> Leave eye through optic nerve

107
Q

Light is converted into what signals?

A

Neural

108
Q

The process of adjusting lens configuration (to bring images into focus) is called…

A

Accommodation

109
Q

Binocular disparity is greatest for…

A

Close objects

110
Q

Visual system uses information provided by receptors around the blind spot, a process called

A

Completion

111
Q

A completion process

Visual system extracts info about edges and infers appearances of large surfaces…

A

Surface interpolation

112
Q

Involuntary eye movements (3)

A

Tremors
Drifts
Saccades

113
Q

What is the retina-geniculate striate pathway?

A

Retina –> primary visual cortex VIA LGN (thalamus)

114
Q

How many layers are there in the LGN?

A

6

115
Q

There are 6 layers in the LGN. What does each layer receive?

A

3 receive input from one eye

3 from the other

116
Q

Lateral inhibition is the finding that when…

A

A receptor fires, it inhibits its neighbours via lateral neural network

117
Q

When is lateral inhibition greatest?

A

When receptor is most intensely illuminated

118
Q

Hubel + Wiesel identified the

A

Receptive field of a visual neuron

119
Q

“The area of the visual field within which it is possible for a visual stimulus to influence firing of that neuron”

A

Receptive field

120
Q

Hubel + Wiesel found that all neurons were _______

A

Monocular

121
Q

Hubel + Wiesel found that all neurons were monocular. This means

A

Each neuron had a receptive field in one eye but not the other

122
Q

Light shone –> produces “on firing” or “off firing” this dependent on whether the cells were

A

Off centre

On centre

123
Q

On centre cells respond to

A

Light shone in central region

124
Q

On centre cells respond to light shone in the central region of receptive field with

A

On firing

125
Q

Off centre cells respond to

A

Light shone in periphery

126
Q

On and off centre cells respond best to

A

Contrast

127
Q

________ neurons are exceptions to the visual field rule (receptive cells).

A

Striate cortex neurons

128
Q

Striate cortex neurons fall into one of two classes:

A

Simple cells

Complex cells

129
Q

Simple cells - what is the receptive field?

A

On/off

Borders are straight lines

130
Q

How to simple cells differ from on/off centre cells?

A

Borders are straight lines rather than circles

131
Q

Complex cells respond to stimulus of

A

A particular ORIENTATION

132
Q

Binocular –> respond to stimulation of

A

Either eye

133
Q

Organisation of the primary visual cortex (2)

A
  1. Functional vertical columns

2. Neurons in same column respond to stimuli applied to same area of retina

134
Q

Colour constancy is a tendency for

A

An object to stay the same colour despite changes in wavelength

135
Q

FIRST STEP in the brain for visual processing?

A

Primary visual cortex

136
Q

Primary visual cortex is the first step in the brain for visual processing. After that, functions become more _____

A

Complex

137
Q

After the primary visual cortex, signals travel to the

A

Secondary visual cortex and visual association cortex

138
Q

After the secondary visual cortex –> output to 2 streams

A

Dorsal stream

Ventral stream

139
Q

Dorsal stream specialises in

A

Visual spatial perception, “where”

140
Q

Ventral stream specialises in

A

Visual pattern recognition, “what”

141
Q

Scotomas are caused by damage to the

A

Primary visual cortex

142
Q

“Ability of patients to respond to visual stimuli in their scotomas despite no conscious awareness”

A

Blindsight

Neuroscience (20 decks)

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