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color vision > 1 > Flashcards

1 Flashcards

1
Q

in prism, most refrangible ray-

least-

A

most-deep violet

least-deep red

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2
Q

T/F: Newton was correct to think you can’t make white light by mixing other colors?

A

False, Huygens showed you can (make white light w/ 2 monochrom lights)

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3
Q

what is newton’s color circle?

A

7 colors: connect 2 colors falls in center of 2; center of circle is white; purple is not on there (violet is not purple) bc not a monochromatic color

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4
Q

metamers?

A

2 colors that look the same but have diff spectral comp.

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5
Q

until late 1700 ppl believed color was a property of light, then who came up w/ what idea?

A

george palmer, involv in phys; made art daylight w/blue glass yellow light=white light

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6
Q

who was the first person to say the trichromacy is in our visual system and light is a cont wavelength?

A

Young;

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7
Q

Dalton thought his color def was due to what?

A

pigmented med in his eye

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8
Q

who figured out complementary colors?

A

helmholtz; 2 comp colors=white

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9
Q

whose idea was it that any monochrom light can be made by using 3 primaries in right proport?

A

maxwell

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10
Q

first to talk about color opp?

A

hering (trichromatic theory=young and helmholtz)

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11
Q

what are the photopig/abs wavelengths for rods and 3 cones?

A

rods-507nm
s cone-cyanolabe 420
m cone-chlorolabe 530
l cone-erythrolabe 560

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12
Q

2 techniques used to measure abs spectra?

A

1) reflection densitometry: bleached retina reflects more light than non-bleached; diff in reflectance before and after bleach
2) microspectrophotometry: for single cone, diff between incident light and measured light

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13
Q

where is photopig in rods vs cones?

A

rods: sep discs
cones: cont membrane that contain it
IS synapses: spherules-rods, pedicles-cones

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14
Q

photopigment mol active when bound w/

A

11 cis retinal

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15
Q

what is isomerization?

A

photon abs by 11 cis retinal then changes to form all trans retinal (has to go thru retinal cycle to get back to 11 cis and be active again)

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16
Q

There is about a __ log unit difference in luminance for wavelength det in our vis syst?

A

16 log unit

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17
Q

First to notice difference in visual perception under different illumination conditions? what colors appear brighter in day vs night?

A

Purkinje; day=red, night=blue

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18
Q

single rod contains ~how much rhodopsin? entire retina?

A

Single rod : Contains about 10^7 rhodopsin molecules

Entire retina: Contains about 10^15 rhodopsin molecules

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19
Q

T/F: scotopic spectral sens function coincides with the rhodopsin absorption spectrum?

A

true very similar overlap

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20
Q

what is the Photochromatic Interval?

A

The difference between the scotopic and photopic spectral sensitivity function
-Scotopic peak ~505nm
-Photopic peak ~555nm
Scotopic is about 100 times more sensitive than the photopic

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21
Q

what is the Principle of Univariance:

A

once a photon is absorbed by a photopigment, the identity of the photon’s wavelength is lost.

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22
Q

2 pathological conditions with just one photopigment:

A

1) Rod monochromatism: Only rods in retina

2) S-cone monochromatism: Only s-cones in retina

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23
Q

T/F: when you have 2nd photopigment it’s possible to tell diff bw wavelengths ind of light intensity

A

true;
The ratios between the responses of the 2 photopigments remain constant no matter the intensity of the wavelengths
The visual system used ratio information to discriminate between wavelengths

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24
Q

what is Grassmann’s Law of Scalar Invariance:

A

If the intensity of one half is changed by k, then the two fields can by matched by changing the intensity on the other half by k
Aka – if you increase the intensity of both field by the same amount, the metamarism is not disrupted – we still have metameric colors

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25
Q

what is Grassmann’s Law of Additivity?

A

If a light is added to one of the fields, then the two fields can be matched by adding the same light to the other half
Aka – if we add the same light on both the top and bottom field – we still have metameric colors

26
Q

Mixing lights causes more wavelengths to be ______

A

Mixing lights causes more wavelengths to be reflected

  • Each light adds wavelengths to the mixture
  • Additive color mixtures
27
Q

what are Subtractive color mixtures?

A

Only wavelengths that are not absorbed by BOTH pigments will be reflected and will give the new color to the mixture of the photopigments

  • Mixing pigments causes fewer wavelengths to be reflected
  • Each pigment subtracts wavelengths from the mixture
28
Q

what is the rec field of a neuron?

A 
Receptive Field (RF) of a neuron in the visual system is the area that influences the neural activity of the cell 
Ex. The RF of a single photoreceptor is their outer segment aperture
29
Q

what is the function of horizontal cells?

A

Connect cones with different cones

  • Each horizontal cell is connected to 7-36 cones – depending on the retinal eccentricity
  • control cone input to bipolar cells
  • Respond greatly to spatial and temporal changes
30
Q

h1 vs h2 horizontal cells:

A

H1 receive input mainly from both L and M-cones

H2 receive input mainly from S-cones, but also from L and M-cones

31
Q

midget bipolar cells: input? description

A
  • input from single L cone in center and multiple M cones in surround
    (or single M cone in center and L cone in surround)
    -Smaller at the central retina (fovea)
    -At larger eccentricities – receive input from more than one L- or M-cone (but always from the same cone type)
32
Q

diffuse bipolar cells: input? description

A

Input from L and M cones
NO COLOR/Magnocellular pathway
No spectral differences because input is received from both L and M in center and surround

33
Q

S bipolar cells: input? description

A

Input from S-cone in center and L and M cones in surround

34
Q

what are the 3 diff rod to bipolar cells interactions?

A

1) Rod-to-rod bipolar cell
2) Rod-to-cone bipolar cell through gap junctions with cones
3) Rod-to-cone ON and OFF bipolar cell

35
Q

Describe the 3 types of ganglion cells?

A

1) Midget
- input from midget bipolar
- Red-green
2) Parasol
- input from diffuse bipolar
- Achromatic
3) Small bistratified
- input from s-cone bipolar
- Blue-yellow

36
Q

3 attributes of color:

A

1) Hue
2) Saturation: vibrancy of the hue (desaturated color is a color that we added white to)
3) Luminance (brightness)

37
Q

There is a range (around ___nm?) that you can not match by adding three primaries – instead you need two primaries and one primary (the red) added to the testing field (“neg” red)

A

500nm

38
Q

what is the CIE rg Chromaticity Diagram?

Whatever falls on the solid curve is a ______?

A

curve represents the color space
-All the wavelengths (spectral lights) are plotted on the outer line “spectral locus”
Whatever falls on the solid curve is a monochromatic light

39
Q

The points: (0,0) (0,1) and (1,0) on CIE correspond to what?

A
  • (0,0) = 435.8nm - blue
  • (0,1) = 546.1nm – green
  • (1,0) = 700nm – red
40
Q

what is the white point on the CIE rg Chromaticity Diagram?

A

White point is at (0.33, 0.33)

  • known as equal energy white – we mostly use this one
  • not the only white point
41
Q

what is luminance on CIE rg Chromaticity Diagram?

A

-vector that is vertical to this plane

All the colors on the 2D color space plan have the same luminance

42
Q

T/F: o Any light that goes through white and ends on both sides of the spectral locus will show complementary colors

A

true

43
Q

what are cardinal directions on the CIE rg Chromaticity Diagram?

A

2 lines correspond to maximum activity of the color opponent cells (90 degrees apart)

44
Q

what are unique hues?

A

Hues that are neither blue or yellow, red or green
-Unique blue, green and yellow are spectral colors –
-monochromatic lights
Unique red falls on the line of purples – not monochromatic
**do not correspond with the cardinal axis/coincide with the max. activation of the cone-opponent cells

45
Q

what is hue cancellation?

A

Created by Hurvich and Jameson

  • technique used to derive the unique hue
  • crossing points are where the lights look neither reddish nor greenish and neither bluish nor yellowish
46
Q

what unique color has largest interobserver variability?

A

Unique green shows the largest inter-observer variability

47
Q

parvo and magno and konio project to what layer of LGN?

A

Parvo- and Magnocellular pathway project to 4C layer of VI

  • Parvocellular projects to sub-layer 4Cb
  • Magnocellular projects to sub-layer 4Ca
  • Koniocellular projects within the 4C also but difficult to identifiy because so few cells
48
Q

what are the 3 theories of color constancy?

A

1) chromatic adaptation-Normalizes the cones responses every time there is an overall change in illumination; o More cones in ora serrata then in mid-periphery
2) surroundings-fails w/o surrounding “keyhole effect”
3) memory

49
Q

new world monkeys: describe region and CV

A

• South and Central America
• On trees
• Color vision is intermediate between trichromatic and dichromatic
o Females – 2/3 trichromatic and 1/3 dichromatic
o Males – all are dichromatic
o New world monkeys have an extra cone (yellow) different from the L and M cones we have

50
Q

old world monkeys: describe region and CV

A
  • Africa and Asia
  • Humans
  • On the ground
  • Color vision is trichromatic
51
Q

The opsin gene for the short wavelength cones (blue) is located in chromosome __ (old/new world monkey)

A

7 (7q32)

52
Q

Genes that encode middle and long wavelength cones are encoded in chromosome ___ (old world monkey)

A

chromosome X (Xq28)

53
Q

In the New World monkeys the X chromosomes carry how many opsin genes?

A

In the New World monkeys the X chromosomes carries only one opsin gene - a single pigment gene

54
Q

what is the “locus control region”?

A

*Region in each chromosome that defines whether short or middle wavelength opsin gene will express in that particular PR
-Why we get random photoreceptor mosaic
(S. L and M cones expression)

55
Q

what are the 2 theories about CV evolut w/ monkeys?

A

1) world separated and old world monkeys followed different evolutionary route than the new world monkeys
- Due to some random process, a duplication occurred and they ended up having two opsin genes
- Another random process occurred and one opsin gene mutated and became a different wavelength gene
* *DNA sequencing revealed that the genome of the middle wavelength cones between the two lineages is so close -theory UNLIKELY

2) Old world monkeys have three genes and a crossover happens

56
Q

what property determine the spectral characteristics of the cones?

A

The amino acid sequence determine the spectral characteristics of the cones

  • L and M cone opsins show 98% similarity in amino acid sequence
  • S-cone opsin shows only 40% similarity with L and M-cone opsins
57
Q

Most common substitution with L and M cones:

A

Most common substitution is serine for alanine on exon 3

58
Q

T/F: Deuteranomalous observers can have nearly normal CV to almost as poor as a deuteranope

A

true:
• The spectral differences between L genes is greater than between M genes
o So deuteranomalous observers will have larger spectral separation in their two cones
o This results in better wavelength discrimination than protanomalous
what does this mean??

59
Q

what is the inh pattern of tritan defects?

A

Tritan deficiencies are autosomal dominant inherited

  • Need just one chromosome for CVD to be expressed
  • usually inc penny
60
Q

The most common cause of complete achromatopsia is a mutation in the _____ gene

A

mutation in the CNGB3 gene

gene encoding a certain protein for ion channels

61
Q

Most common CVD you will encounter is:

A

deuteranomly

color vision (1 decks)

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