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Brain and Behaviour > Chapter 5 - Vision > Flashcards

Chapter 5 - Vision Flashcards

1
Q

How do you see an object?

A

You see an object when it omits or reflects light that stimulates receptors that transits information to your brain.

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2
Q

What did Johannes Muller discover?

A

The law of specific nerve energies - whatever excites a particular nerve establishes a special kind of energy unique to that nerve.

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3
Q

What is the law of specific energies?

A

Whatever excites a particular nerve establishes a special kind of energy unique to that nerve.

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4
Q

What do sensory neurons rely on?

A

Frequency of coding

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5
Q

How does light flow to a receptor?

A

Light enters the brain through the pupil, is then focused by the lens and cornea (not adjustable) and projected onto the retina. The retina is lined with visual receptors.

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6
Q

How does light travel from receptors to the brain?

A

Messages go from receptors to bipolar cells which send messages to ganglion cells which axons join together and travel back to the brain.

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7
Q

What are amacrine cells?

A

They get information from bipolar cells and send it to other bipolar, amacrine and ganglion cells.

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8
Q

What is a blind spot?

A

Point where ganglion axons join to form the optic nerve where no receptors are.

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9
Q

What is the fovea?

A

The point of eye specialised for detail (i.e. reading). The fovea receptors connect to a single bipolar cell which connects to a single ganglion cell with an axon to the brain. These are called midget ganglion cells as they are so small.

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10
Q

What are midget ganglion cells?

A

The ganglion cells that connect bipolar cells that are connected to fovea receptors. They are so small.

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11
Q

What are rods?

A

Rods are abundant in the periphery. They respond to faint light but not useful in daylight as bright light bleaches them.

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12
Q

What are cones?

A

Cones are abundant in and near the fovea. They are useful in bright light and are essential for colour vision.

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13
Q

What are photopigments?

A

Rods and cones contain photopigments. Photopigments are chemicals that release energy when struck by light. They consist of 11-cis-retinal bound to proteins called opsins. Light converts 11-cis-retinal to all-trans-retinal-releasing energy that activates secondary messengers in the cell.

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14
Q

What do photopigments consist of?

A

They consist of 11-cis-retinal bound to proteins called opsins.

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15
Q

What wavelengths do we perceive light as?

A

We perceive light with a short wavelength (400nm) as violet and longer (700nm) as red.

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16
Q

What is the trichromatic theory of colour vision?

A

Young-Helmholtz theory - we perceive colour through the relative rates of response by three kinds of cones, each one minimally sensitive to a different set of wavelengths. Blue, red and green cones. Blue is distributed evenly but is the least common. Red and green are haphazardly distributed.

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17
Q

What is the Young-Helmholtz theory?

A

The trichromatic theory of colour vision - we perceive colour through the relative rates of response by three kinds of cones, each one minimally sensitive to a different set of wavelengths. Blue, red and green cones. Blue is distributed evenly but is the least common. Red and green are haphazardly distributed.

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18
Q

What is the opponent-process theory?

A

We see colours in terms of opposites.

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19
Q

What is the retinex theory?

A

The cortex compares information from various parts of the retina to determine brightness and colour for each area.

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20
Q

What is colour blindness?

A

People fail to develop one type of cone or an abnormal type of cone.

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21
Q

Where does the optic nerves meet?

A

At the optic chiasm where half the axons from each eye cross to the opposite side of the brain.

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22
Q

Where does information from the nasal sie of the eye go to?

A

Information from the nasal side of each eye crosses to the contralateral side.

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23
Q

Where do most ganglion cells go to?

A

The lateral geniculate nucleus - part of the thalamus.

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24
Q

Where is the lateral geniculate nucleus

A

Thalamus.

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25
Q

What does the lateral geniculate nucleus do?

A

It sends axons to other parts of the thalamus and the visual cortex.

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26
Q

What is lateral inhibition?

A

When a receptor is excited, it sends an excitatory signal to the bipolar cell and the horizontal cell. The horizontal cell spreads wide and has an inhibitory effect. The horizontal cell inhibits the cell beside the bipolar cell creating a contrast.

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27
Q

What does a horizontal cell do?

A

The horizontal cell spreads wide and has an inhibitory effect. The horizontal cell inhibits the cell beside the bipolar cell creating a contrast.

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28
Q

What is the receptive field of a ganglion cell like?

A

It has a circular centre with an antagonistic doughnut-shaped surround (i.e. the outside might inhibit the cell).

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29
Q

What are parrocellular neurons?

A

Small cell bodies and small receptive fields that are mostly in or near the fovea.

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30
Q

What are magnocellular neurons?

A

Larger cell bodies and receptive fields that are spread evenly throughout the retina.

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31
Q

What are koniocellular neurons?

A

Small cell bodies but occur throughout the retina.

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32
Q

Where does information from the lateral geniculate nucleus go?

A

To the primary visual cortex in the occipital cortex (area V1) or the striate cortex.

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33
Q

What is a simple cell?

A

A receptive field with fixed excitatory and inhibitory zones. The more light that shines in excitatory zone the more the cell responds.

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34
Q

What are complex cells?

A

Responds to a pattern of light in a particular orientation anywhere within receptive field.

35
Q

What are end-stopped or hypercomplex cells?

A

Has an inhibitory zone at one end of bar-shaped receptive field.

36
Q

What do neurons in area V1 detect?

A

They detect spatial frequencies rather than bars or edges.

37
Q

How do cells with similar properties group together?

A

Cells with similar properties group together in the visual cortex in columns perpendicular to the surface.

38
Q

What does area V1 do?

A

The primary visual cortex (area V1) sends information to the secondary visual cortex (area V2) which processes the information further and sends it to additional areas.

39
Q

What is the ventral stream?

A

It identifies and recognises objects through the temporal cortex. (what stream)

40
Q

What is the dorsal stream

A

It identifies the importance of movement through the parietal cortex. (where/how stream)

41
Q

What happened with Women DF?

A

Carbon monoxide poising resulted in damage to the pathways between the visual cortex and temporal cortex. Was impaired at recognising faces, identifying shape and orientation of objects and reading.

42
Q

What happened with JS?

A

Damage to temporal lobe. Was impaired at recognising faces, identifying shape and orientation of objects and reading.

43
Q

What does the inferior temporal cortex do?

A

Responds to meaningful objects.

44
Q

What is visual agnosia?

A

An inability to recognise objects despite satisfactory vision. Results from damage to temporal cortex.

45
Q

What part of the brain responds to pictures of places?

A

Parahippocampal cortex.

46
Q

What part of the brain responds to pictures of faces?

A

Fusiform gyrus.

47
Q

What is prosopagnosia?

A

Impaired ability to recognise faces.

48
Q

What is Area V4 important for?

A

Recognising colour

49
Q

What are the medial temporal cortex and Area V5 and the medial superior temporal cortex important for?

A

Motion perception. Areas MT and MST mainly receive input from the magnocellular path which detects patterns including movement over the visual field. The magnocellular path is colour insensitive.

50
Q

What do medial temporal cells detect?

A

Acceleration or deceleration and absolute speed. They also detect photos of movement.

51
Q

What does MST do?

A

Responds to expansion, contraction, or rotation of a large visual scene.

52
Q

What is motion blindness?

A

The ability to see objects but impairment at seeing whether they are moving, or if so, how fast and in what direction.

53
Q

What are saccades?

A

Voluntary eye movements. Area MT is suppressed during these.

54
Q

The one additional feature that hypercomplex cells have that complex cells do not is that:

A

hypercomplex cells have a strong inhibitory area at one end of its receptive field.

55
Q

If a kitten is reared in an environment consisting entirely of horizontal lines, the visual cortex becomes:

A

sensitive to almost nothing but horizontal lines.

56
Q

Infants with cataracts need to have surgical repair:

A

as early as possible.

57
Q

The lateral geniculate nucleus is part of the:

A

Thalamus

58
Q

Magnocellular cells are to ____ as parvocellular cells are to ____.

A

Movement; colour

59
Q

____ are chemicals that release energy when struck by light.

A

Photopigments.

60
Q

People with motion blindness probably have suffered damage to the:

A

Middle-temporal cortex

61
Q

The primary visual cortex is also known as the:

A

Striate cortex

62
Q

The name of the point at which the optic nerve leaves the retina is called the:

A

Blind spot

63
Q

A person with damage to V1, but not V4, would be able to perceive:

A

Motion, but not shape or colour

64
Q

Cutting the left optic nerve in front of the optic chiasm would result in blindness in ____.

A

The left eye

65
Q

Once within the cerebral cortex, the magnocellular pathway continues as a pathway sensitive to:

A

Movement

66
Q

The receptive field of a receptor is the:

A

point in space from which light strikes the receptor.

67
Q

The ability to recognize that a door maintains its shape even though the shape of the image on the retina is changing is known as:

A

Shape constancy

68
Q

According to the opponent-process theory, under what circumstances would you perceive a white object as blue?

A

If you stared at a bright yellow object for a minute or so and then looked at a similar white object, it would appear blue.

69
Q

Where does the optic nerve start and where does it end?

A

It starts with the ganglion cells in the retina. Most of its axons go to the lateral geniculate nucleus of the thalamus; some go to the hypothalamus and superior colliculus.

70
Q

When light strikes a receptor, does the receptor excite or inhibit the bipolar cells? What effect does it have on horizontal cells? What effects does the horizontal cells have on bipolar cells?

A

The receptor excites both the bipolar cells and the horizontal cell. The horizontal cell inhibits the same bipolar cell that was excited plus additional bipolar cells in the surround.

71
Q

If light strikes only one receptor, what is the net effect (excitatory or inhibitory) on the nearest bipolar cell that is directly connected to that receptor? What is the effect on bipolar cells to the sides? What causes that effect?

A

It produces more excitation than inhibition for the nearest bipolar cell. For surrounding bipolar cells, it produces only inhibition. The reason is that the receptor excites a horizontal cell, which inhibits all bipolar cells in the area.

72
Q

As we progress from bipolar cells to ganglion cells to later cells in the visual system, are receptive fields ordinarily larger, smaller, or the same size? Why?

A

They become larger because each cell’s receptive field is made by inputs converging at an earlier level.

73
Q

What are the differences between mango cellular and parvocellular systems?

A

Neurons of the parvocellular system have small cell bodies with small receptive fields, are located mostly in and near the fovea, and are specialised for detailed and colour vision. Neurons of the magnocellular system have large cell bodies with large receptive fields, are located in all parts of the retina, and are specialised for perception of large patterns and movement.

74
Q

What do cells within a column of the visual cortex have in common?

A

They respond best to lines in the same orientation. Also, they are similar in their preference for one eye or the other, or both equally.

75
Q

What is a feature detector?

A

It is a neuron that detects the presence of a particular aspect of an object, such as a shape or a detection of movement.

76
Q

What is the effect of closing one eye early in life? What is the effect of closing both eyes?

A

If one eye is closed during early development, the cortex becomes unresponsive to it. If both eyes are closed, cortical cells remain somewhat responsive for several weeks and then gradually become more sluggish and unselective in their responses.

77
Q

What early experience would cause a kitten or human child to lose stereoscopic depth perception?

A

If the eye muscles cannot keep both eyes focused in the same direction, the developing brain loses the ability for any neuron in the visual cortex to respond to input from both eyes. Instead, each neuron responds to one eye or the other. Stereoscopic depth perception requires cells that compare the input from the two eyes.

78
Q

What causes astigmatism?

A

Astigmatism results when the eyeball is not quite spherical. As a result, the person sees one direction of lines more clearly than the other.

79
Q

Suppose someone can describe an object in detail but stumbles and fumbles when trying to walk toward it and pick it up. Which is probably damaged, the dorsal path or the ventral path?

A

The inability to guide movement based on vision implies damage to the dorsal path.

80
Q

For what items does the brain have specialised areas for perceiving?

A

The temporal cortex has specialised areas for perceiving places, faces and bodies, including bodies in motion.

81
Q

The ability to recognise faces correlates with the strength of connections between which brain areas?

A

The ability to recognise faces correlates with the strength of connections between the occipital face area and the fusiform gyrus.

82
Q

What is colour constancy? What areas is important for it?

A

Area V4. It is the ability to recognise the colour of an object despite changes in the lighting.

83
Q

When you move your eyes, why does it not seem as if the world is moving?

A

Neurons in areas MT and MST respond strongly when an object moves relative to the background and not when the object and background move in the same direction at the same speed.

84
Q

Under what circumstances does someone with an intact brain become motion blind, and what accounts for the motion blindness?

A

People become motion blind shortly before and during a saccade (voluntary eye movement), because of suppressed activity in area MT.

Brain and Behaviour (10 decks)

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