Color Vision

1
Color Vision
Sang Wook Hong
2
Neural Pathway of Color Processing
Color Appearance local and global processing
Color Binding
3
Neural Pathway of Color Processing
Color Appearance local and global processing
Color Binding
4
Neural Signals from Retina
5
Neural Pathway for Color Processing
Parallel Processing Hypothesis Livingstone
Hubel (1987)
V4 color
MT
Retinal ganglion cells
Parvocellular color selective low temporal
resolution low contrast sensitivity high
spatial resolution
Depth
form
LGN
color
Depth
form
form
color
Primary visual cortex
form
Depth
1
color
color
color
2 3
form
form
4A
Visual area 2
movement
4B
Magnocellular color blind high temporal
resolution high contrast sensitivity low
spatial resolution
4C
5
6
6
LGN Projection
7
Neural Signals in V1
8
Neural Signals in V1
Landisman TSO (1999)
9
Neural Signals in V1
Conway (2001)
10
Neural Signals in V2
Moutoussis Zeki (2002)
11
Neural Signals in V4
Zeki Marini (1998)
12
Neural Pathway of Color Processing
Color Appearance local and global processing
Color Binding
13
Chromatic Induction

• Color appearance of a light can be altered in
  the presence of a surrounding light. This
  phenomenon is referred to as chromatic induction.

• Chromatic contrast The color of the light
  appears to change in a direction away from the
  color of the surrounding light

• Chromatic assimilation The color of the light
  appears to change in a direction toward the color
  of the surrounding light

14
Chromatic Contrast
15
Chromatic Assimilation
CHROMATIC ASSIMILATION
CHROMATIC ASSIMILATION
16
Chromatic Assimilation
CHROMATIC ASSIMILATION
CHROMATIC ASSIMILATION
17
Induction from Patterned Backgrounds
Monnier Shevell (2003, 2004)
18
Induction from Patterned Backgrounds
Monnier Shevell (2003, 2004)
19
S-cone Center-Surround Receptive Field
S
-S
BACKGROUND CONDITION
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Local Global Processing
21
Local Global Processing
22
Local Global Processing
Hourglass Structure
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Experimental Setup
Test Surround 15cd/m2
Comparison Surround 15cd/m2
Test Square 20cd/m2
11 min
Comparison Square
1.9?
5.5?
5.5 ?
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Experimental Setup
Test Surround 15cd/m2
Comparison Surround 15cd/m2
Inducing Bars 20cd/m2
1.9?
5.5?
5.5 ?
25
Results
Surround chromaticities
Obs. S.X.
s S/(LM)
l L/(LM)
26
Results
Surround chromaticities
s S/(LM)
l L/(LM)
27
Results
Surround chromaticities
s S/(LM)
l L/(LM)
28
Neural Pathway of Color Processing
Color Appearance local and global processing
Color Binding
29
Fundamental Question
Is binding necessary?
30
Separate Processing Hypothesis
Livingstone Hubel (1987)
Retinal ganglion cells
Parvocellular color selective low temporal
resolution low contrast sensitivity high
spatial resolution
LGN
Magnocellular color blind high temporal
resolution high contrast sensitivity low
spatial resolution
31
Separate Processing Hypothesis
Livingstone Hubel (1987)
V4 color
MT
Retinal ganglion cells
Parvocellular color selective low temporal
resolution low contrast sensitivity high
spatial resolution
Depth
form
LGN
color
Depth
form
form
color
Primary visual cortex
form
Depth
1
color
color
color
2 3
form
form
4A
Visual area 2
movement
4B
Magnocellular color blind high temporal
resolution high contrast sensitivity low
spatial resolution
4C
5
6
32
Separate Processing Hypothesis
Physiological support for Specific Color Pathway

• A large concentration of color opponent cells in
  the CO blobs in V1
• Livingstone Hubel (1984)

• A concentration of color opponent cells in thin
  CO-bands in V2
• Hubel Livingstone (1987), Tso, Roe Gilbert
  (2001)

• Cerebral achromatopsia
• Zeki (2003)

33
Combined Processing Hypothesis
Multi-selective cells

• The same concentration of color opponent cells
  in all CO-bands in V2
• Gegenfurtner, Kiper Fenstemaker (1996)

• Color selective cells are tuned also to
  orientation
• Kiper, Fenstemaker Gegenfurtner(1997)

• Most color-luminance cells in V1 are tuned also
  to orientation
• Johnson, Hawken Shapley (2001)

• Orientation selective cells in V1 are also
  sensitive to chromatic variation
• Friedman, Zhou von der Heydt (2003)

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Multi-selectivity and Color Perception
If the response is 5 spikes/sec, then
35
Incorrect Binding
Illusory Conjunction (Treisman Schmidt, 1982)