Colour Vision 1 + 2 Flashcards
1
Q
What are the problems with perception?
A
- The environment
- The reality
- The sensory system of the brain
2
Q
What is an example of a challange that comes with perception?
A
If there is a vast amount of information in the environment, it is tough for the brain to perceive all the information at once.
The greater the stimuli, the harder it is.
3
Q
Cognitive resources are ___ ___, which are quickly ___.
A
scarcely, limited, depleted
4
Q
Give two examples of visual records within the visual system.
A
- Vison is not rich in detail, eye movements are goal-directed.
- Mental imagery used the same brain areas as teh visual perception system.
5
Q
Eye movement are goal-directed meaning ___.
A
That vision is not a passive process.
6
Q
Name three types of ganglion cells.
A
- Midget cells.
- Bistratified.
- Parasol cells.
7
Q
What is the purpose of midget cells?
A
Midget cells are a type of ganglion cell, they project to the parvocellular layers of the lateral geniculate nucleus.
8
Q
Where are midget cells found?
A
They are found in the ganglion layer of the retina.
9
Q
What colour channel are the midget cells responsible for?
A
The red-green colour channel.
10
Q
What colour channel are bistratified cells responsible for?
A
The blue-yellow colour channel.
11
Q
Where are bistratified ganglion cells found?
A
They are found in the ganglion layer of the retina.
12
Q
What are two kinds of bistratified ganglion cells.
A
13
Q
Where are parasol cells located?
A
In the ganglion cell layer in the retina.
14
Q
What is another name for parasol cells?
A
M-cells.
15
Q
Define vision perception.
A
Vision perception is the brains’ ability to receive, interprut and act upon visual stimuli.
16
Q
What are the seven elements that perception is based on?
A
- Visual descrimination.
- Visual memory.
- Visual-spatial relationships.
- Visual form constancy.
- Visual sequential memory.
- Visual figure/ground.
- Visual closure.
17
Q
Define visula discrimination.
A
Visual discriminatio is the ability to distinguish from one shape from another.
18
Q
Define visual memory.
A
Visual memory is the ability to remember a specific form when it is removed from your visual field.
19
Q
Define visual-spatial relationships.
A
Visual-spatial relationships is the ability to recognise forms that are the same but different in a different spatial orientation.
20
Q
Define visual form constancy.
A
Visual form constancy is the ability to discern similiar forms that are the same but may be different in size, colour, or spatial orientation and to consistantly match the similar form.
21
Q
Define visual sequenctial memory.
A
Visual squential memory is the ability to recall two to seven items in a sequence with vision occluded.
22
Q
Define visual figure/ground.
A
Visual figure/ground is the ability to discern forms when camouflaged or partially hidden.
23
Q
Define visual closure.
A
Visual closure is the ability to recognise familiar forms that are only partially completed.
24
Q
What are the six layers of the lateral geniculate nucleus.
A
- Magnocellular
- Magnocellular
- Parvocellular
- Parvocellular
- Parvocellular
- Parvocellular
25
What are M-cells?
M-cells are neurons located within the adina magnocellular layer of the lateral geniculate nucleus of the hypothalamus.
26
What are P-cells?
P-cells are neurons located within the parvocellular layers of the lateral geniculate nucleus of teh thalamus.
27
What are K-cells?
K-cells are neurons with a small cell body located in the konicellular layer of the lateral geniculate nucleus (the part between the six layes).
28
What is the V1, V2, V3, V4, V5 selective for?
They are selective for the following:
* Orientation.
* Colour.
* Binocular disparity.
* Motion direction.
29
What does the visual system: V1 selective for?
It is involved in:
* Colour contrast.
* Achromatic contrast.
* Ocular dominance columns.
* Orientation columns.
30
What is binocular disparity?
Binocular disparity refers to the difference in image location of an object seen by the left and right eyes resulting from the eyes’ horizontal separation (parallax).
31
What are the visual processing streams and anatomical pathways?
Dorsal and ventral
Magnocellular and parvocellular
Stimulus attributes:
* M: motion, depth: larger
* P: form, colour: smaller
32
Why is there connectivity between the processing streams and anatomical pathways?
For:
* Efficient communication
* Integration of information
33
What pathway does the object discrimination task refer too?
*(Ungerleider and Mishkin, 1983)*
The 'what pathway.'
34
What pathway does the landmark discrimination task refer too?
*(Ungerleider and Mishkin, 1983)*
The 'where pathway'.
35
Perceptions are an ___ process and they imform us about ___ aspects of our \_\_\_.
active, important, environment.
36
Representations of objects are \_\_\_, in a layered way, by ___ sub-systems.
constructed, specialised.
37
Visual perception is special as it ___ \_\_\_ about ___ objects.
conveys messages, distant
38
Perceptions aid ___ as they enable us to take ___ and ___ when it comes to spotting predators, food, or healthy mates.
survival, decisions, actions
39
Why do we need colour vision and what is it?
* Colour is about communication.
* About object segregation.
* Perceptual words depend on the beholder which also depends on the species. Humans are trichromats.
* There is no such thing as color, it is a construct that is based on physics, e.g., sunlight hitting an object and generating a colour by reflecting it (‘what pathway’). If the individual has stored knowledge, they decide what to do with it.
40
Name the three different cones.
S, M, and L cones.
41
Where does S cones lay?
They lay on a specific chromosome.
42
What does S-cones stand for?
Short wavelength cone.
43
What does M-cones stand for?
Medium wave-length cone.
44
What does L-cones stand for?
Long wavelength cone.
45
What are S-cones mediated by? and what chromesome?
They are mediated by a gene on the band called q38 on the chromosome 7.
46
What are M-cones mediated by? and what chromesome?
M-cones are mediated on the X chromosome on a band called q28 (q = long arm).
47
What is the percentages/ratios of the cones in the fovea?
Typically there are twice as many L-cones as M-cones and S-cones only make up around 5% (the structure is random).
48
What is a complex cell?
A cell type of the visual cortex that responds best to a light stimulus of a particular shape anywhere in its receptive field; its receptive field cannot be mapped into fixed excitatory and inhibitory zones
49
What is a cone?
A type of retinal receptor that contributes to color perception
50
What is the dorsal stream?
The dorsal stream is the visual path in the parietal cortex, sometimes known as the where or how pathway
51
What is the lateral geniculate nucleus?
A thalamic nucleus that receives incoming visual information.
52
What is the primary visual cortex area: V1?
An area of the cortex responsible for the fi rst stage of visual processing.
53
Define prosopagnosia.
An impaired ability to recognize or identify faces.
54
What is a cone?
A type of retinal receptor that does not contribute to color perception.
55
What is a saccade?
A saccade is the ballistic movement of the eyes from one fixation point to another.
56
What is the secondary visual cortex area: V2?
It is an area of the visual cortex responsible for the second stage of visual processing
57
What is a bipolar cell?
A bipolar cell is a type of neuron in the retina that receives input directly from the receptors.
58
Why does negative colour afterimage occur?
It occurs as a result of staring at a coloured object for a prolonged length of time and then looking at a white surface, the image is seen as a negative image, with a replacement of red with green, green with red, yellow and blue with each other, and black and white with each other.
59
Define ppponent-process theory.
The idea that we perceive colour in terms of opposites.
60
What is the ventral stream?
The ventral stream is visual paths in the temporal cortex that are specialised for identifying and recognising objects; the "what" pathway.
61
What is visual agnosia?
Visual agnosia is an inability to recognise objects despite otherwise satisfactory vision.
62
What is a simple cell?
A type of visual cortex cell that has a receptive field with fixed excitatory and inhibitory zones.
63
What is the V3 area?
The area of the secondary association cortex of the visual cortex - recognises moving shapes.
64
What is the V4 area?
An area of the visual cortex particularly important for colour constancy and visual attention.
65
What does V5 area detect?
It detects motions.
66
What are the six different steps/stages of the visual pathway?
1. Optic nerve.
2. Optic chasim.
3. Optic tract.
4. Lateral geniculate nucleus.
5. Optic radiations.
6. Primary visual cortex.
67
What does the posterior parietal cortex do?
It keeps track of the position of the body relative to the world.
68
What is the prestriate cortex?
The band of tissue in the occipital lobe that surrounds the primary visual cortex and contains areas of secondary visual cortex.
69
What is the inferotemporal cortex?
A cortex of the inferior temporal lobe, in which is located an area of secondary visual cortex.
70
What is the inferotemporal cortex involved in?
It is involved in object recognition.
71
Define trichromatic theory?
Colour perception occurs through the relative rates of response by the three kinds of cones. Each cone is maximally sensitive to a different set of wavelengths.
72
Afterimage phenomenon may be closely related to ___ \_ \_\_\_, which allows a rapid series of pictures to portray motion. This is the basis of animation & cinema.
persistence of vision
73
What does red-green deficity result from?
It results from the long- & medium-wavelength cones having the same photopigment.
74
What is topographical mapping?
Nearby parts of visual space are represented at nearby anatomical locations in the primary visual cortex (V1)
75
The LGN also controls how much of the signal actually gets to the cortex. It provides "\_\_\_ \_\_\_" function, i.e., has internal inhibitory circuits that can selectively turn individual signals off and regulate exactly which visual information is passed through to the cortex.
gate keeper
76
Some people with damage to V1 show \_\_\_, an ability to respond to visual stimuli that they report not seeing. So, awareness may be occurring prior to V1.
blindspot
77
What is the secondary visual cortex?
The area of the visual cortex that receives signals for analysis of motion, shape, position, etc. Different regions are responsible for different types of classification and analysis.
78
What is the ventral stream?
The ventral stream is the area in which information is relayed from the V2 to the secondary temporal cortex.
79
What is the dorsal stream?
The dorsal stream is the area in which information is relayed from the V2 to the secondary parital cortex.
80
What two pathways make up the ventral stream?
The magnocellular and parvo-cellular pathways .
81
What pathway is the ventral stream? 'What' or 'Where'?
What
82
What causes visual agnosia?
Caused by damage to pattern pathway from the V1 to inferior temporal cortex (i.e., ventral stream).
83
What are three visual pathways in cerebral cortex?
1. Parvocellular neuron pathway.
2. Magnocellular neuron pathway.
3. A mixed pathway.
84
What is the parvocellular pathway sensitive to?
Details of shapes.
85
What is the magnocellular pathway sensitive to?
Movement.
86
What is the mixed pathway sensitive to?
Brightness and colour.
87
Describe anomalous trichromacy.
Limited discrimination, but still contains all three photopigments.
88
Describe deurteranomolous trichromacy.
Sensitivity spectrums hifted to longer wavelengths. Green weak. Requires more green to match.
89
Describe tritanomaly.
Inherited blue-yellow wavelength spectrum shift. More rare.
90
Describe monochromatism.
Rare condition of not being able to distinguish colours. They only have one retinal cone or lack all cone function/rod monochromat.
91
Describe protanope.
Red deficient/lack erythrolabe - sensitivity reduced in the higher wavelengths.
92
Describe deuteranope.
Green deficient/lack chlorolabe.
93
Who are most likely to have red/green colour defects?
* Males.
* Bilateral and stable.
94
What is the cause of acquired blue/yellow colour defects?
Outer retinal disease
95
What is the cause of acquired red/green colour defects?
Inner retina/optic nerve or visual pathway abnormalities, asymmetric or unilateral, progressive.
96
What does the Ishihara test for?
Red/Green colour deficiency only.
97
What tests are available for colour vision in practice?
Ishihara and the city colour vision test (city university test)
98
What does the City test for?
All colour vision problems.
99
Talk through the Ishihara plates...
1. The test starts with a demonstration plate - which can be seen by all.
2. 2nd is the transformation plates - a different number will be seen by patients with red/green deficiency compared to normals.
3. We then progress onto a vanishing plate set - meaning that only normal colour vision patients will see a number.
4. Hidden plates are then seen - no number for normal colour vision but red/green deficiency will see a number.
5. Diagnostic plates follow - these are to differentiate between red / green deficiency (deu and pro).
6. Finally we have the tracing plates which can only be seen by those with colour deficiency (red/green) and can be done by tracing the lines... OR there may ONLY be a line for those with normal colours, and none / the wrong line for colour deficiency.
100
What is the rarest type of colour deficiency?
Monochromacy - extremely unlikely. No colour perception at all, and often have to wear sunglasses in normal lighting conditions.
101
What is red/green colour blind?
Deutranopia and protanopia.
102
What is red/green colour deficiency?
Red/green colour deficiency is the term used for anyone who has deutranomoly or protanomoly.
103
## Footnote
What are the colour vision problem types (i.e. colours etc...)
* Protanopia - no ability for red.
* Protanomoly - reduced red.
* Deutranopia - no ability for green.
* Deutranomoly - reduced geen. (most common)
* Tritanopia - no ability for blue.
* Protanomoly - reduced ability for blue.
104
What is the most common type of colour vision problem?
Deutranomolous (anomolous deutranopia) which accounts to around 5% of the 8% of colour blind men.
105
What is the max absorption wavelength for long, medium and short?
(between 400-600 nm)
* Long: 560 nm
* Medium: 530 nm
* Short: 420 nm
106
Which are FALSE about the Trichromatic Theory? (Pick 2)
A) Colour is determine by the magnitude and ratio of stimulation of L, M, S cones
B) Each photoreceptor does not determines colour
C) If only one cone present can still descriminate based on wavelength
D) If only one cone present, you can discriminate between stimulus based on intensity and percent absorbed
E) Absorption and Neural effects are both dependent on wavelength
C) and E) are FALSE
Can not descriminate color on the basis of wavelength if only one type of cone present
E) Neural effect is independent of wavelength. response is inside the photoreceptor (hyperpolarization).
107
How did trichomats come about?
There was a duplication of the L-cone and one of them mutated to becomes the M-cone.
108
How much of their genome does L and M-cones share?
Around 98%.
109
Describe intergenic recombination.
Causes dichromacy.
The genes misalign because they are so similar, they recombin and end up with no M-cones.
110
Describe intragenic recombination.
Causes anomalous trichromacy
Teh genes misalign, tehy recombine with half (approx) of each gene and from a hybrid gene instead of an M.
111
What genes did a female carrier of anomalous trichromacy inherit?
They inherited the hybrid gene alongside the normal one.
112
Which cone photoreceptors contribute to brightness perception?
A. Long
B. Medium
C. Short
D. All of the above
D. All of the above
113
Describe the B-Y opponent colour channel and what color appears with more long/medium, short and balanced wavelengths.
(What wavelength receptors it recieves stimulation from, does it recieve input from an intermediate channel)
* Recieves stimulation from long, medium and short wavelength
* Long and medium wavelengths input into an intermediate channel (Yellow)
* Stimulate more long, medium wavelengths will look yellow
* Stimulate more short wavelength will look blue
* Stimulate balanced wavelength will look white
114
What are the signals organized in the Opponent Theory to form final colour perception?
(What happens to the R-G, B-Y signals? Is there a Color Mixing?)
* Final color perception is a combination of R-G and Y-B opponent channels
* There is no colour mixing at this stage. Purely a neural reponse
115
Interactions between medium and long wavelengths in the cone is completely a neural response. (i.e. No colour addition/subtraction) TRUE/FALSE?
TRUE
116
What role does the magnocellular visual pathway play in colour vision?
A. Luminance
B. Red-Green
C. Blue-Yellow
D. Recieves information from midget ganglion cells (cones)
E. Has opponent cells
A. Luminance
Magnocellular has no role in colour perception
117
What role does the parvocellular visual pathway play in colour vision? (Pick 3)
A. Luminance
B. Red-Green
C. Blue-Yellow
D. Receives information from midget ganglion cells (cones)
E. Has opponent cells
B. Red-Green
D. Receives information from midget ganglion cells (cones)
E. Has opponent cells
118
What role does the konio (small bistratified) gangion cells play in colour vision? (Pick 2)
A. Luminance
B. Red-Green
C. Blue-Yellow
D. Receives information from midget ganglion cells (cones)
E. Has opponent cells
C. Blue-Yellow
E. Has opponent cells
119
Where in the neural system does colour vision occur?
(Which part of the brain?)
- Primary Visual Cortex (Striate Cortex and V1)
120
What is cerebral chromatopsia?
(How does it occur, which part of the brain it affects, what is affected)
* Stroke damage near calcarine sulcus
* Affects colour perception
* Without cerebral function, no colour vision
121
Monochromats are unable to make wavelength based discriminations? TRUE/FALSE
TRUE
122
What test is used to measure individual differences in colour vision?
Rayleigh match.
123
124
What are colours dependant on?
They are dependant on context.
125
Temporal context is an example of what?
Chromatic adaptation.
126
Spatial context is an example of what?
Chromatic contrast.
127
What is colour good for?
Colour is good for providing individuals with information regarding objects, for example, what the object is made out of.
128
What do contextual effects contribute to?
Colour constancy.
129
Colour constancy maks colour a ___ signal ___ for recognising \_\_\_.
reliable, objects
130
Distinguish between the sensory and physical properties of colour.
SENSORY - hue, saturation, brightness.
PHYSICAL - wavelength, intensity (difference between peaks and troughs, brighter/darker).
131
What are 2 evolutionary functions of colour discrimination?
1. Detection.
2. Signalling.
132
What is the visible spectrum?
* 400-700nm.
* Short = blue.
* Long = red.
* White = mixture.
* Black = absence of light so no wavelength value.
133
What is meant by "chromatic" light?
* All the wavelengths.
* Selective reflection of light off of an object - some reflected more than others e.g. if blue is reflected most we see a blue object.
* We can represent this using REFLECTANCE CURVES.
134
What is meant by monochromatic and achromatic light?
* MONO = Light source only emits a single wavelength anyway.
* ACHROM = Light composition spread across visible spectrum i.e. object has no hue (white, black or grey).
135
How do we see colour in transparent objects?
SELECTIVE TRANSMISSION - creation of chromatic colour by selectively transmitting some wavelengths e.g. cranberry juice selectively transmits long wavelengths.
136
What is meant by an additive colour mix?
Happens when mixing lights - remember that white surfaces reflect all wavelengths. So, when lights superimposed on white wall we see all of their reflectance so we see white light/
137
When is colour vision possible?
* In dichromats i.e.those with 2 pigments (not possible with one).
* In trichromats a wider range of colours are able to be seen across the visible spectrum.
138
What is believed to be responsible for our colour constancy abilities?
* Chromatic adaptation - Prolonged exposure to tungsten light bleaches the long wavelength cone pigments (adaptation) so we have decreased sensitivity to long wavelengths and so less effect occurs.
* Effect of surroundings - Constancy is harder when surroundings are masked, works best when other colours visible (mechanism not certain yet).
* Memory - knowledge about an object's "usual" colour.
139
