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Biopscyhology > Vision - Chapter 5 > Flashcards

Vision - Chapter 5 Flashcards

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1
Q

Trichromatic Theory of Colour Vision was created by who?

A
  • Young & Helmholtz
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2
Q

What is the Trichromatic Theory of Colour Vision

A

Colour is perceived through the relative rates of response by three kinds of cones, each one maximally sensitive to a different set of wavelengths.

This ratio of responses among the three cones determines a perception of a specific colour.

The perception depends on the frequency of response in one cell relative to the frequency of another cell.

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3
Q

What type of cells allows for colour vision?

A

Cone cells

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4
Q

Where are colour vision cells located?

A

In and around the Foveal

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5
Q

What are photopigments?

A

Chemicals (11 cis retinal and opsin) in rod and cone cells that are released by light and modifying the photopigments into wavelengths

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6
Q

How is colour vision possible?

A

Colour vision results from electromagnetic radiation (wavelengths) that are detected by our cones.

wavelengths range from shortest to longest

any colour is the result of mixing 3 wavelengths

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7
Q

What is the range of colours from the longest wavelength to the shortest?

A

shortest to longest ROY G. BV

red> orange> yellow> green> blue> violet>

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8
Q

What is the visual field?

A

the part of the world you see in your peripheral vision before you see colour

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9
Q

What is the negative colour afterimage?

A

It is the replacement of a colour after overexposure with the opposite colour in the wavelength

it requires the full context of colour

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10
Q

What are the three theories of Colour Vision?

A

Trichromatic theory

Opponent Process theory

Retinex theory

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11
Q

What is the Opponent-Process Theory of Colour Vision

A

In response to negative afterimage

Colour is perceived on a continuum of opposites

red is opposite to green
yellow to blue
white to black

a fatigued response to overexposure in one colour results in the visualization of a second colour

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12
Q

Opponent-Process Theory of Colour Vision was created by

A

Hering

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13
Q

Retinex Theory

A

A response to the failure of other theories to explains colour consistency

The cortex compares information from the various retina. Brightness and perceived colour are determined by comparing light reflected by the object itself and adjacent surfaces.

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14
Q

What is colour consistency

A

the ability to recognize colour despite changes in ambient light

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15
Q

Who proposed the Retinex Theory

A

Land

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16
Q

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

A

If you were overexposed to yellow object then looked at a picture of a similar white object it would appear blue.

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17
Q

What is color vision deficiency (color blindness)

A

colour vision deficiency is a genetic condition.

It is the inability to specific wavelengths of colour.

colour blindness is the inability to see any colour other than black and white - it is rare.

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18
Q

When a television set is off, its screen appears gray. When you watch a program, parts of the screen appear black, even though more light is actually showing on the screen than when the set was off. What accounts for the black perception?

A

According to the retinex theory the black experience arises by contrast with the other brighter areas. The contrast occurs by comparison within the cerebral cortex.

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19
Q

Colour perception

A

is dependent on both the wavelength of light from a given spot but also the light from surrounding areas (Context).

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20
Q

What is the process for processing visual images in the brain?

A

light>rods/cones>Horizontal cells>Inhibitory contact with bipolar cells - amacrine and ganglia cells

ganglia cell axons> join to form optic nerve

Optic nerve splits axons at the optic chasim- 1/2 to right/1/2 to left hemisphere

Optic nerve ganglia) >communicate with lateral geniculate nucleus (in thalamus), superior colliculus in Perinteal lobe and Hypothalamas

Lateral geniculate nucleus communicates with the > visual cortex (posterior of occipital lobe)

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21
Q

What is LATERAL INHIBITION?

A

Lateral inhibition heightens contrast and emphasizes the borders of objects by the reduction of activity in one neuron yet activating neighbouring neurons in the retina.

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22
Q

How does lateral inhibition work?

A

Rod/cone receptors in the retina are stimulated by light

exciting both a horizontal and primary bipolar cell

Horizontal cell inhibits the primarily bipolar cell but excites bipolar cells lateral to the primary bipolar cell.

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23
Q

What are photoreceptors

A

They are the rod and cone cells at the back of the retina that receive light

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24
Q

What is a receptive field?

A

Is a group of photoreceptors that are excited or inhibited based on the pattern of light being received. Therefore there are excitatory receptive fields and Inhibitory receptive fields

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25
What cells are excited in the excitatory or "on-centre" Receptor fields
When light hits the centre of a group of cells in a receptor field, those cells are excited while the surrounding cells are inhibited
26
What cells are excited in the inhibitory or "off-centre" Receptor fields
When light hits the area around the centre of a group of cells in a receptor field, those cells receiving light are excited while the cells in the centre are inhibited
27
How many categories of Ganglion cells are there and what are they called
3 categories Parvocellular neurons Magnocellulare neurons Koniocellular neurons
28
What is a Parvocellular neuron?
located in or close to the fovea, they are small cells with small receptive field. They detect visual detail and colour
29
What is a Magnocellular neuron?
Located equally throughout the retina they are large cells that detect movement and patterns
30
What is a koniocellular neuron?
Located equally throughout the retina, they are small cells - they have several functions
31
Lateral Genicular nucleus
located in the Thalamus - most ganglion axons of the eye connect to the lateral genicular nucleus. Similar to the receptive fields of the ganglia they have both excitatory and inhibitory centres
32
What is V1 and where is it located
V1 is the primary visual cortex located at the posterior of the occipital lobe. It is responsible for conscious vision and real, imagined or dreamt visual images.
33
What is blindsight
the ability to navigate objects in the world after damage to the V1. There is no conscious sight.
34
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?
They become larger because each cell’s receptive field is made by inputs converging at an earlier level.
35
What are the differences between the magnocellular and parvocellular systems?
Parvolcellular systems are comprised of small cells located in and around the fovea and are responsible for seeing detail and color. Magnocelluar systems are cells located somewhat equally throughout the retina and are responsible for detecting movement and patterns.
36
Continuous flash suppression
a procedure where one sees a flashing object in one eye and a steady object in the other eye - resulting in the conscious viewing of the flashing image and unconscious viewing of the steady image.
37
If you were in a darkened room and researchers wanted to “read your mind” just enough to know whether you were having visual fantasies, what could they do?
Researchers could use fMRI, EEG, or other recording methods to see whether activity increased in your primary visual cortex.
38
What is an example of an unconscious response to visual information?
blindsight -someone can point toward an object or move the eyes toward the object, despite insisting that he or she sees nothing.
39
What shape are receptive cells in the retina and lateral genicular nucleus?
Circular
40
What shape are the receptive cells in the occipital lobe?
Bar shaped
41
Hubel and Weisel discovered how many types of receptor cells are there in the occipital lobe and what are did they called them?
There are 3 types of cells 1) simple cells - respond to colour and detail 2) complex cells - respond to movement and patterns 3) end-stopped or hypercomplex cells - respond to movement and patterns
42
What are the characteristics of the simple cell in the occipital lobe?
Small cell - Located in V1 of visual cortex has a receptive field with fixed excitatory and inhibitory location of a stimuli. Therefore responds to a stimulus in only one fixed location is a simple cell more light in the excitatory zone, = cellular responds. more light in the inhibitory zone = less the cellular responds. More simple cells respond to horizontal or vertical orientations than to diagonal.
43
What are the characteristics of the complex cell in the occipital lobe?
Medium sized - Located in V1 & V2 or visual cortex A complex cell responds to a pattern of light in a particular orientation. Therefore responds equally stimuli throughout a large area Response to movement and patterns
44
What are the characteristics of the end-stopped cell in the occipital lobe?
Large sized Similar to complex responds to patterns and movement. Except the outlying areas of the bar has an inhibitory response
45
How are cells organized within the visual cortex?
Cells with similar properties (i.e. they process similar information) are organized in columns perpendicular to the surface of the visual cortex.
46
How could a researcher determine whether a given neuron in the visual cortex is simple or complex?
First identify a stimulus and present the stimulus in several locations. If the cell responds strongly in only one location, it is a simple cell. If it responds in several locations, it is a complex cell.
47
What do cells within a column of the visual cortex have in common?
They respond best to lines in the same orientation. They are also similar in their preference for one eye or the other, or both equally.
48
What is the waterfall illusion and what does it demonstrate?
If you stare at a waterfall for a time and then look away, the objects next to the waterfall appear to flow upward. Demonstrates Feature detectors and works because prolonged exposure to a given visual feature decreases sensitivity to that feature, as if it fatigued the relevant detectors.
49
What is a feature detector cell and what does it require?
feature detector cells are neurons wthat detects the presence of a particular aspect of an object, such as a shape or a direction of movement. They require feedback from other cortical areas of the brain. A top down process that reorganizes activity in the Primary visual cortex (V1)
50
Why do most visual researchers believe that neurons in V1 detect spatial frequencies rather than bars or edges?
because most cortical neurons respond best to a particular spatial frequency and hardly at all to other frequencies
51
What is the course of visual development in People?
visual properties are formed in utero as a result of spontaneous activity in the retina. These properties are fine tuned with visual experience after birth.
52
What is binocular input
Input in both eyes
53
What happens if one eye is deprived of stimulation from birth
synapses in the visual cortex become unresponsive in the deprived eye once open the eye does not respond to it. If deprevation is later in life the response to the deprived eye is weakened.
54
What happens if both eyes are deprived of stimulation from birth
If both eyes are closed, cortical cells remain somewhat responsive for several weeks and then gradually become sluggish and unselective in their responses.
55
What is a sensitive period?
It is a time when experiences have a particularly strong and enduring influence. For aspects of visual experience the sensitive period ends with the onset of certain chemicals that stabilize synapses and inhibit axonal sprouting. However Cortical plasticity is greatest in early life, but it never ends.
56
What is stereoscopic depth perception?
It is the comparison of inputs from both eyes.
57
What is retinal disparity?
the discrepancy between what the left and right eyes see.
58
What is strabismus or lazy eye?
a condition in which the eyes do not point in the same direction. Both eyes are active, but they do no send the same message.
59
What is one possible treatment fo Strabisums (lazy eye)?
Video games
60
What early experience would cause a kitten or human child to lose stereoscopic depth perception?
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.
61
What happens if human infants are exposed mainly to vertical or horizontal lines instead of both equally?
They become more sensitive to the kind of line they have seen.
62
What is astigmatism? a blurring of vision for lines in one direction (e.g., horizontal, vertical, or one of the diagonals), caused by an asymmetric curvature of the eyes.
a blurring of vision for lines in one direction (horizontal, vertical, or one of the diagonals).
63
What causes astigmatism?
an asymmetric curvature of the eyes.
64
If an infant is born with dense cataracts on both eyes and they are surgically removed years later, how well does the child see at first?
The child can see enough to identify two objects as thesame or different, but the child doesn’t understand what the visual information means
65
What is the order of connections from receptors to visual cortex?
Receptors—bipolar cells—ganglion cells—lateral geniculate—visual cortex
66
Axons from the nasal half of the retina go to the ___ hemisphere of the brain. Axons from the temporal half of the retina go to the ___ hemisphere of the brain.
contralateral . . . ipsilateral
67
When light strikes a receptor, the effect is to ___ the bipolar cells and ___ the horizontal cells. The horizontal cells___ the bipolar cells.
excite . . . excite . . . inhibit
68
If light strikes one receptor, the net effect is to ___ the nearest bipolar cell and ___ other bipolar cells to the side because of the contributions from ___ cells.
excite . . . inhibit . . . horizontal
69
Suppose light strikes the retina in a circle, surrounded by dark. Which bipolar cells will show the greatest response, and which will show the least?
Bipolars connected to the receptors just inside the circumference of the circle respond most. Those connected to receptors just outside the circumference respond least.
70
As we progress from bipolar cells to ganglion cells to later cells in the visual system, what happens to the size of receptive fields?
They become larger.
71
In contrast to parvocellular neurons, magnocellular neurons are more sensitive to ______.
movement
72
If you were in a darkened room and researchers wanted to know whether you were having visual fantasies (without asking you), they could measure activity in which brain area?
The primary visual cortex
73
What is meant by blindsight
Some people with damage to the primary visual cortex accurately guess the location or other properties of objects they say they don’t see
74
How could a researcher determine whether a given neuron in the visual cortex is simple or complex
If it responds to a stimulus in just one location, it is a simple cell. If it responds in several locations, it is a complex cell.
75
What do cells within a column of the visual cortex have in common?
They respond best to lines in the same orientation.
76
What is the evidence that certain types of feature detectors operate in the human visual cortex
After you stare at a waterfall or other steadily moving display, you see stationary objects as moving in the opposite direction.
77
What early experience is necessary to maintain binocular input to the neurons of the visual cortex?
Cortical cells must usually receive simultaneous input from the two eyes.
78
Why is it important to correct astigmatism early?
The visual cortex becomes more sensitive to the lines it sees best.
79
If someone is born with dense cataracts on both eyes, and the cataracts are removed years later, which of these aspects of vision remains permanently impaired?
Motion perception and depth perception
80
How does the brains visual system operate on a need-to-know basis
Different parts of your brain receives input from different aspects of an object including shape, colour, distance and movement. There are at least 80 brain areas that contribute to vision in different ways.
81
What is the secondary visual cortex (V2)
V2 is located in front of V1 (which is at the posterior of the occipital lobe). V2 receives information from V1 and returns information to V1.
82
What is the ventral stream?
The ventral stream runs through the temporal cortex and is responsible for recognizing and identifying objects
83
What is the dorsal stream?
The dorsal stream runs through the parietal lobe and supports visually guided movements
84
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?
in the dorsal stream

Biopscyhology (1 decks)

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