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 orange yellow green blue indigo violet
5 Wavelength in meters
108 AC circuits 106 Wavelength in Nanometers
104 Broadcast band red 102 700
1 orange
Radar -2 10 600 yellow
10-4 Infrared rays green -6 10 The visible spectrum 500
Ultraviolet rays blue 10-8 indigo -10 10 X rays 400 violet
10-12 Gamma rays
10-14 6 Image by MIT OpenCourseWare. 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
G R 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
10 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
12 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
ON OFF ON OFF
time 18 Midget and blue/yellow systems
cones
H
ON OFF ON OFF ON OFF ON OFF ON OFF bipolars
A IPL, OFF IPL, ON
YELLOW BLUE ON OFF BLUE YELLOW ON OFF
Green ON and OFF Yellow/blue Blue/yellow Red ON and OFF ganglion cells ganglion cell ganglion cell 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 45 135 45 Spikes per Second
0 0 180 10 20 30 40 50 60 180 20 40 60 80 100
225 315 225 315
270 270
Green OFF cell Red ON cell 90 90
135 45 135 45
180 0 180 0 10 20 30 40 10 20 30 40 50
225 315 225 315 maintained discharge rate 270 270 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
70
60
50
40 Percent Correct Percent
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 DEPTH DEPTH FORM FORM FORM TEXTURE TEXTURE TEXTURE MOTION MOTION 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.
32 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
200
2.7
400
200 1.7 Number of Spikes 400
200 1.1 400
200
0.7
Image by MIT OpenCourseWare. 34 Isoluminant color grating
35 Luminance grating
36 Responses of an MT cell to luminance and chrominance differences
Chrominance
40
20
0 Spikes per second 0 1600 0 1600 0 1600 0 1600 ms Percent color contrast 2 4 8 16
Luminance
40
20
0 Spikes per second 0 1600 0 1600 0 1600 0 1600 ms Percent luminance contrast 2 4 8 16
Image by MIT OpenCourseWare. 37 Responses of an MT cell to luminance and chrominance differences
Chrominance
50
25
Spikes per second 0 0 1450 0 1450 0 1450 0 1450 ms
2 4 8 16 Percent color contrast
Luminance
50
25
Spikes per second 0 0 1450 0 1450 0 1450 0 1450 ms
2 4 8 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 rods cones
photo- receptors
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
photo- receptors
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
photo- receptors
OPL
ON OFF ON
IPL AII ON OFF amacrine
incoming light to CNS
50 Response of a retinal ganglion cell at various background adaptation levels
400
300 background log cd/m2 -5 -4 -2-3 -1 0
200 Discharge rate (spikes/sec) rate Discharge 100
0 -5 -4 -3 -2 -1 0 Test flash (log cd/m2)
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
G R 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 MIT OpenCourseWare http://ocw.mit.edu
9.04 Sensory Systems Fall 2013
For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.