Color vision and adaptation
1
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?
2
Color vision
3
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 psychological
attributes 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 the
sum of the luminances of the components.
4
Newton's prism experiment
(1672 at age 29)
red
red
orange
yellow
green
blue
indigo
violet
5
Wavelength in meters
8
10
AC circuits
6
10
Wavelength in Nanometers
104
Broadcast
band
2
10
700
orange
1
10
-2
10-4
10
Radar
600
-6
yellow
green
Infrared rays
The visible spectrum
500
blue
Ultraviolet rays
10
red
-8
10
-10
10
-12
indigo
X rays
400
violet
Gamma rays
10
-14
Image by MIT OpenCourseWare.
6
Image removed due to copyright restrictions.
Please see lecture video or the C.I.E. chromaticity diagram from 1931.
7
The color circle
Y
hue
Hue
R
G
Saturation
B
Image by MIT OpenCourseWare.
8
The color circle
Image removed due to copyright restrictions.
Please see lecture video or Figure 3 of Derrington, Andrew M., John Krauskopf,
et al. "Chromatic Mechanisms in Lateral Geniculate Nucleus of Macaque." The
Journal of Physiology 357, no. 1 (1984): 241-65.
9
Major theories of color vision
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Young-Helmholtz theory
There are three types of broadly tuned color receptors. The color
experienced 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 antagonistic
pairs, with the third pair being black and white.
Earlier Leonardo da Vinci: "Of different colors equally perfect, that will appear most
excellent 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.
11
Basic physiology of color processing
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Image removed due to copyright restrictions.
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.
Labeled blue cones
contain calcium-binding
protein calbindin-D28k
13
Image removed due to copyright restrictions.
Please refer to lecture video.
14
Since only one out of eight cones is blue, the
spatial resolution of the blue cones is lower
15
The absorbtion spectra of photorecptors
16
The absorbtion spectra of photorecptors
Image removed due to copyright restrictions.
Please see lecture video or Figure 2 of Dartnall, H. J. A., J. K. Bowmaker,
et al. "Human Visual Pigments: Microspectrophotometric Results from the
Eyes of Seven Persons." Proceedings of the Royal Society of London. Series
B. Biological Sciences 220, no 1218 (1983): 115-30.
Microspectrophotometry
How much light of various
wavelengths is absorbed
by single cones and rods
17
MIDGET SYSTEM
PARASOL SYSTEM
or
Neuronal response profile
OFF
ON
time
ON
OFF
18
Midget and blue/yellow systems
cones
H
ON
OFF
OFF
ON
ON
OFF
ON
OFF
ON
OFF
bipolars
A
IPL, OFF
IPL, ON
ON
OFF
Green ON and OFF
ganglion cells
YELLOW
BLUE
Yellow/blue
ganglion cell
BLUE
YELLOW
Blue/yellow
ganglion cell
ON
OFF
Red ON and OFF
ganglion cells
19
Color selectivity in the LGN
20
Response to Different Wavelength Compositions in LGN
Blue ON cell
Yellow ON cell
90
90
135
135
45
45
Spikes per Second
180
10 20 30 40 50 60
225
0
180
315
20 40 60 80 100
225
270
Red ON cell
90
90
135
135
45
10
225
20
30
315
270
315
270
Green OFF cell
180
0
40
0
45
180
10 20 30 40 50
225
maintained discharge rate
0
315
270
21
Major classes of midget cells in primate retina
Red ON
Red OFF
Green ON
Green OFF
Blue ON
Yellow ON
22
The effects of lesions
on color vision
23
Coronal section of monkey LGN
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.
24
25
Image by MIT OpenCourseWare.
Color discrimination
26
Color Discrimination
100
90
80
Percent Correct
70
60
50
40
30
20
10
0
NORMAL
V4
PLGN
NORMAL
MLGN
Seneca, V4, PLGN and MLGN lesions
Image by MIT OpenCourseWare.
27
Color discrimination with varied color saturation
Low saturation
Higher saturation
28
Color saturation discrimination
Image removed due to copyright restrictions.
Please refer to lecture video or Schiller, Peter H. "The Effects of V4 and Middle
Temporal (MT) Area Lesions on Visual Performance in the Rhesus Monkey."
Visual Neuroscience 10, no. 4 (1993): 717-46.
29
Perception at isoluminance
30
At isoluminance vision is compromised
DEPTH
FORM
TEXTURE
MOTION
DEPTH
FORM
TEXTURE
MOTION
DEPTH
FORM
TEXTURE
MOTION
31
Texture, Motion and Stereo
Image removed due to copyright restrictions.
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 in
Perception at Isoluminance." Neuropsychologia 29, no. 6 (1991): 443-41.
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Neuronal responses at isoluminance
33
The response of a group of magnocellular LGN cells to color exchange
MAGNO CELLS
R/G
400
200
4.2
400
Number of Spikes
200
2.7
400
200
1.7
400
200
1.1
400
200
0.7
Image by MIT OpenCourseWare.
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Isoluminant color grating
35
Luminance grating
36
Responses of an MT cell to luminance and chrominance differences
Spikes per second
Chrominance
40
20
0
0
1600 0
1600 0
1600 0
1600 ms
Percent color contrast
2
4
8
16
Spikes per second
Luminance
40
20
0
0
1600 0
1600 0
1600 0
1600 ms
Percent luminance contrast
2
4
8
16
Image by MIT OpenCourseWare.
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Responses of an MT cell to luminance and chrominance differences
Spikes per second
Chrominance
50
25
0
0
1450
0
2
1450
0
4
1450
1450 ms
0
8
16
Percent color contrast
Spikes per second
Luminance
50
25
0
0
1450
2
0
1450
0
4
1450
8
1450 ms
0
16
Percent luminance contrast
Image by MIT OpenCourseWare.
38
Color blindness and tests for it
39
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)
40
Ishihara plate #2. Do you see an 8 or a 3?
Image is in public domain.
41
Image removed due to copyright restrictions.
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.
42
43
44
Farnsworth - Munsell color test
Arrange in hue order
Four rows of 20 each
farnsworth munsell color test online
45
Adaptation
46
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.
47
pigment epithelium
cones
rods
photoreceptors
OPL
cone horizontal
H
ON
OFF
bipolars
ON
IPL
AII
ON
OFF
amacrine
ganglion cells
incoming light
to CNS
48
Effective connections under light adapted conditions
pigment epithelium
cones
photoreceptors
OPL
cone horizontal
H
ON
OFF
bipolars
IPL
ON
OFF
ganglion cells
incoming light
to CNS
49
Effective connections under dark adapted conditions
pigment epithelium
rods
photoreceptors
OPL
ON
ON
OFF
IPL
AII
ON
incoming light
OFF
amacrine
to CNS
50
Response of a retinal ganglion cell at various background adaptation levels
400
background
log cd/m2
Discharge rate (spikes/sec)
300
-5
-4
-3
-2
-1
0
200
100
0
-5
-4
-3
-2
Test flash (log cd/m2)
-1
0
Image by MIT OpenCourseWare.
51
The after-effects of adaptation
stabilized images
afterimages
52
PERCEPTION AND SYSTEM RESPONSE BEFORE AND AFTER ADAPTATION
Image removed due to copyright restrictions.
Please refer to lecture video or Schiller, Peter H., and Robert P. Dolan. "Visual
Aftereffects and the Consequences of Visual System Lesions on their Perception
in the Rhesus Monkey." Visual Neuroscience 11 no. 4 (1994): 643-65.
54
Y
hue
Hue
R
G
Saturation
B
Image by MIT OpenCourseWare.
55
off axis
57
hue
saturation
58
Photograph removed due to copyright restrictions.
Please refer to lecture video or see John Sadowski's big Spanish castle illusion.
59
Image removed due to copyright restrictions.
Please refer to lecture video or see John Sadowski's big Spanish castle illusion.
60
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 Systems
Fall 2013
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