1 Physics 1230: Light and Color Lecture 14: The retina and brain, image signal processing. Reading : Chap. 9,10 Color perception. Exam 4 cancelled : Exam extra credit assignment will be due Wed. at 5PM Extra credit to improve exam scores! Final HWs : Due today, Tuesday, 5PM
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Physics 1230: Light and Color
Lecture 14: The retina and brain, image signal
processing.
Reading: Chap. 9,10 Color perception.
Exam 4 cancelled: Exam extra credit
assignment will be due Wed. at 5PM
Extra credit to improve exam scores!
Final HWs: Due today, Tuesday, 5PM
The remaining lectures:
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• Ch. 7 (Retina and visual perception),
• Ch. 9 & 10 (color & color perception).
We
are
here
Ch. 7 – Visual Perception
• Parts of the visual processing system
• Lightness and brightness
• Retinal processing: Lateral inhibition
• Hermann grid
• Receptive field
• Motion illusion
• Craik O‟Brien illusion &
simultaneous lightness contrast
• Other optical illusions
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We
are
here
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The Retina: Detecting the light and processing the images
Has 108 nerve endings to detect image
rods, for high sensitivity (night vision)
cones, for color and detail, 7 million
optic nerve = 106 transmission lines
fovea, region of best vision (cones)
The retina and optic nerves are recognized as actually
parts of the brain (like your olifactory bulb in the nose).
They start development IN the brain and migrate…
More nerves in your retina than some creatures
have in their entire brains. Processing Power.
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Rods and cones
• Rhodopsin, a photochemical, responds to lightIt is destroyed and reformed.Signal goes to a synapse, a gap between nerve cells
• There are 3 kinds of cones for 3 colors
red, green, blue (more later).
A great deal is understood about how the
individual cells of the retina receive light, respond
to light, and transmit signals.
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Rods and cones
We will skip Most of cellular detail BECAUSE…
Example: Rhodopsin and photosensitivity
Photo-responsive membrane
protein is known in atomic detail
Light drives a change in
molecular shape.
Opens/closes membrane
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Does our understanding of the individual rods, cones,
and other cells of the retina do much to explain this?:
(A) Creitanly (B) Myaby Not Mcuh
We need to understand how NETWORKS of
cells WORK TOGETHER to let us perceive.
Layers of the retina
9Light
Layers of the retina
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Layers of the
retina are
CROSS
Connected
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a, The rods (R) and cones (C) convey visual information to the ganglion cells (G) through the bipolar cells (B). Horizontal cells (H)
allow lateral connections between rods and cones. Amacrine cells (A) allow lateral connections between bipolar and ganglion cells.
The optic nerve is formed from the axons of all the ganglion cells. A subset of ganglion cells (MG cells) also detects light directly; for
this, they require the photopigment melanopsin, as now confirmed1, 2, 3. b, Light, via melanopsin, causes changes in Ca2+ levels in
MG cells9 (a fluorescent Ca2+ indicator was used here). Counterintuitively, light passes through the transparent ganglion layer to
reach the rods and cones.
From the following article:Neurobiology: Bright blue times