Post on 18-May-2018
Color vision and adaptation
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Central questions about color vision and adaptation:
1. What are the basic facts and laws of color vision?
2. What are the major theories of color vision?
3. How is color processed in the retina and the LGN?
4. How is color processed in the cortex?
5. What is the nature of color blindness?
6. How is adaptation achieved in the visual system?
7. What are afterimages?
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Color vision
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Basic facts and rules of color vision
1. There are three qualities of color: hue, brightness, saturation
2. There is a clear distinction between the physical and psychologicalattributes of color: wavelength vs. color, luminance vs. brightness.
3. Peak sensitivity of human photoreceptors:S = 420nm, M = 530nm, L = 560nm, Rods = 500nm
4. Grassman's laws:1. Every color has a complimentary which when mixed properly yields gray.2. Mixture of non-complimentary colors yields intermediates.
5. Abney's law:The luminance of a mixture of differently colored lights is equal to thesum of the luminances of the components.
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Newton's prism experiment(1672 at age 29)
red
yellowgreenblue
orange
indigoviolet
red
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red
orang
yello
green
blue
indigo
violet
AC circuits
Broadcastband
Radar
Infrared rays
Ultraviolet rays
X rays
Gamma rays
Wavelength in meters
Wavelength in Nanometers
The visible spectrum
108
106
104
102
10-2
10-4
10-6
10-8
10-10
10-12
10-14
700
600
500
400
1 e
w
Image by MIT OpenCourseWare. 6
Image removed due to copyright restrictions.
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Please see lecture video or the C.I.E. chromaticity diagram from 1931.
hue
Saturation
Y
B
RG
Hue
The color circle
Image by MIT OpenCourseWare.
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The color circle
Image removed due to copyright restrictions.
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Please see lecture video or Figure 3 of Derrington, Andrew M., John Krauskopf,
et al. "Chromatic Mechanisms in Lateral Geniculate Nucleus of Macaque." TheJournal of Physiology 357, no. 1 (1984): 241-65.
Major theories of color vision
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Young-Helmholtz theory
There are three types of broadly tuned color receptors. The colorexperienced is a product of their relative degree of activation.Problems: Fails to explain Grassman's laws.
Hering's theory
Theory of color opponency based on the observation that red and green as well as blue and yellow are mutually exclusive. The nervous system probably treats red/green and blue/yellow as antagonisticpairs, with the third pair being black and white.
Earlier Leonardo da Vinci: "Of different colors equally perfect, that will appear mostexcellent which is seen near its direct contrary...blue near yellow, green near red:because each color is seen, when opposed to its contrary, than to any other similar to it.
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Basic physiology of color processing
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Image removed due to copyright restrictions.
Labeled blue cones
contain calcium-bindingprotein calbindin-D28k
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Please see lecture video or Figure 1 of De Monasterio, F. M., E. P. McCrane, et al."Density Profile of Blue-sensitive Cones Along the Horizontal Meridian of Macaque
Retina." Investigative Ophthalmology & Visual Science 26, no. 3 (1985): 289-302.
Image removed due to copyright restrictions.
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Please refer to lecture video.
Since only one out of eight cones is blue, the spatial resolution of the blue cones is lower
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The absorbtion spectra of photorecptors
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The absorbtion spectra of photorecptors
Image removed due to copyright restrictions.
Microspectrophotometry
How much light of various wavelengths is absorbedby single cones and rods
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Please see lecture video or Figure 2 of Dartnall, H. J. A., J. K. Bowmaker,et al. "Human Visual Pigments: Microspectrophotometric Results from theEyes of Seven Persons." Proceedings of the Royal Society of London. Series
B. Biological Sciences 220, no 1218 (1983): 115-30.
MIDGET SYSTEM PARASOL SYSTEM
ON OFF ON OFF
Neuronal response profile
time
or
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Green ON and OFF ganglion cells
Red ON and OFF ganglion cells
cones
Midget and blue/yellow systems
OFF OFF bipolars
H
A
ON
OFFON
OFF ONOFF OFF
IPL, OFFIPL, ON
ON OFF ONON
Blue/yellow ganglion cell
BLUEYELLOW
Yellow/blue ganglion cell
YELLOW BLUEON OFF
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Color selectivity in the LGN
20
30 400
45
90
135
180
225 315
270
50 40 60 800
45
90
135
180
225 315
270
Spikes per Second
Response to Different Wavelength Compositions in LGNBlue ON cell Yellow ON cell
20 1006010 20
200
45
90
135
180
225 315
270
10 20 30 400
45
90
135
180
225 315
270maintained discharge rate
10
Green OFF cell Red ON cell
5030 40
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Major classes of midget cells in primate retina
Red ONRed OFFGreen ONGreen OFFBlue ONYellow ON
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The effects of lesions on color vision
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Coronal section of monkey LGN
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Image removed due to copyright restrictions.
Please refer to lecture video or Figure 4a of Schiller, Peter H., and Edward J.Tehovnik. "Visual Prosthesis." Perception 37, no. 10 (2008): 1529.
Image by MIT OpenCourseWare.25
Color discrimination
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100
90
80
70
60
50
40
30
20
10
0NORMAL PLGN NORMAL MLGNV4
Perc
ent C
orre
ct
Seneca, V4, PLGN and MLGN lesions
Color Discrimination
Image by MIT OpenCourseWare.
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Low saturation Higher saturation
Color discrimination with varied color saturation
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Color saturation discrimination
Image removed due to copyright restrictions.
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Please refer to lecture video or Schiller, Peter H. "The Effects of V4 and MiddleT emporal (MT) Area Lesions on Visual Performance in the Rhesus Monkey."Visual Neuroscience 10, no. 4 (1993): 717-46.
Perception at isoluminance
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DEPTH FORMTEXTURE MOTION
DEPTH FORMTEXTURE MOTION
At isoluminance vision is compromised
DEPTH FORMTEXTURE MOTION
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Texture, Motion and Stereo
Image removed due to copyright restrictions.
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Please refer to lecture video or Figure 3, 4 of Schiller, Peter H., Nikos K.Logothetis, et al. "Parallel Pathways in the Visual System: Their Role inPerception at Isoluminance." Neuropsychologia 29, no. 6 (1991): 443-41.
Neuronal responses at isoluminance
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MAGNO CELLS
400
200
200
200
200
200
400
400
400
400
R/G
4.2
2.7
1.7
1.1
0.7
Num
ber o
f Spi
kes
Image by MIT OpenCourseWare. 34
The response of a group of magnocellular LGN cells to color exchange
Isoluminant color grating
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Luminance grating
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Chrominance
Luminance
Percent color contrast
Percent luminance contrast
Spik
es p
er se
cond
Spik
es p
er se
cond
40
20
0
40
20
0
0
0 0 0 0
0 0 01600
1600 1600 1600 1600
1600 1600 1600 ms
ms
2
2
4
4
8
8
16
16
Image by MIT OpenCourseWare. 37
Responses of an MT cell to luminance and chrominance differences
0 1450
50
25
00 1450 0 1450
50
25
00 1450 0 1450 0 1450 0 1450
0 1450
2 4 8 16
2 4 8 16
Chrominance
Percent color contrast
Percent luminance contrast
Luminance
Spik
es p
er se
cond
Spik
es p
er se
cond
ms
ms
Image by MIT OpenCourseWare.
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Responses of an MT cell to luminance and chrominance differences
Color blindness and tests for it
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Color blindness
1. Incidence: males: 8/100 in whites, 5/100 in asians, 3/100 in africans females: frequency 10 times less
2. Types: protanopes: lack L cones deuteranopes: lack M cones tritanopes: lack S cones
3. Color tests: Ishihara plates Farnsworth-Munsell Hue Test Dynamic computer test (City University Dynamic Color Vision Test)
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Ishihara plate #2. Do you see an 8 or a 3?
Image is in public domain. 41
Image removed due to copyright restrictions.
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Please refer to lecture video or adapted from Figure 1 from Barbur, J. L., A. J. Harlow, et al.
"Insights into the Different Exploits of Colour in the Visual Cortex." Proceedings of the Royal
Society of London. Series B: Biological Sciences 258, no. 1353 (1994): 327-34.
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Farnsworth - Munsell color test
Arrange in hue order
Four rows of 20 each
farnsworth munsell color test online45
Adaptation
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Basic facts about adaptation
1. Range of illumination is 10 log units. But reflected light yields only a 20 fold change (expressed as percent contrast).
2. The amount of light the pupil admits into the eye varies over a range of 16 to 1. Therefore the pupil makes only a limited contribution to adaptation.
3. Most of light adaptation takes place in the photoreceptors.
4. Any increase in the rate at which quanta are delivered to the eye results in a proportional decrease in the number of pigment molecules available to absorb those quanta .
5. Retinal ganglion cells are sensitive to local contrast differences, not absolute levels of illumination.
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IPL
amacrine
AII
OPL
rods
ON OFF ONbipolars
ON OFFganglion cells
to CNS
Hcone horizontal
receptors
pigment epithelium
incoming light
photo-
cones
receptors
pigment epithelium
photo-
conesrods
ON OFFganglion cells
H
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IPL
OPL
ON OFF bipolars
ON OFFganglion cells
to CNS
Hcone horizontal
receptors
pigment epithelium
incoming light
photo-
cones
pigment epithelium
Effective connections under light adapted conditions
ON OFF
incoming light49
IPL
OPL
receptorsphoto-
pigment epithelium
AII
ON
rods
amacrine
ON OFF
to CNS
ON OFF
Effective connections under dark adapted conditions
incoming light50
400
300
200
100
0-5 -4 -3 -2 -1 0
Dis
char
ge ra
te (s
pike
s/se
c) 0-1-2-3-4-5backgroundlog cd/m2
Test flash (log cd/m2)
Image by MIT OpenCourseWare.
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Response of a retinal ganglion cell at various background adaptation levels
The after-effects of adaptation
stabilized images afterimages
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PERCEPTION AND SYSTEM RESPONSE BEFORE AND AFTER ADAPTATION
Image removed due to copyright restrictions.
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Please refer to lecture video or Schiller, Peter H., and Robert P. Dolan. "VisualAftereffects and the Consequences of Visual System Lesions on their Perceptionin the Rhesus Monkey." Visual Neuroscience 11 no. 4 (1994): 643-65.
hue
Saturation
Y
B
RG
Hue
Image by MIT OpenCourseWare.
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off axis
57
saturation
hue
58
Photograph removed due to copyright restrictions.
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Please refer to lecture video or see John Sadowski's big Spanish castle illusion.
Image removed due to copyright restrictions.
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Please refer to lecture video or see John Sadowski's big Spanish castle illusion.
Summary:1. There are three qualities of color: hue, brightness, and saturation.
2. The basic rules of color vision are explained by the color circle.
3. The three cone photoreceptors are broadly tuned.
4. Color-opponent midget RGCs form two cardinal axes, red/green and blue/yellow.
5. The midget system is essential for color discrimination.
6. The parasol cells can perceive stimuli made visible by chromiance but cannot ascertain color attributes.
7. Color is processed in many cortical areas; lesion to any single extrastriate structure fails to eliminate the processing of chrominance information.
8. Perception at isoluminance is compromised for all categories of vision.
9. The most significant aspects of luminance adaptation occur in the photoreceptors.
10. Afterimages are a product of photoreceptor adaptation and their subsequent response to incoming light. 61
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9.04 Sensory SystemsFall 2013
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