Date post: | 22-Dec-2015 |
Category: |
Documents |
Upload: | helena-butler |
View: | 236 times |
Download: | 1 times |
Color Vision
Topic 4: Anatomical and Physiological Basis of Color Vision
Happy Valentine!
Outline
• Anatomy of human eye• Retinal Circuitry
Anatomy of Human Eye
http://www.youtube.com/watch?feature=player_detailpage&v=Z8asc2SfFHMb
Retinal Circuitry
Photoreceptors
Rods• 100 million, rich in periphery• Highly sensitive, operating at
dim lights• Poor spatial, temporal vision• Poor color vision
Cones• 8 million, rich in fovea• Less sensitive, operating at
bright light• Good spatial, temporal vision• Good color vision
Photoreceptors
ScotopicRods alone
PhotopicCones alone
MesopicRods & Cones
Stockman & Sharpe 2006, Based on Design of Hood & Finkelstein, 1986
Rod and Cones (Dark-Adaptation Curve)
Rods and Cones (Increment Threshold)
Rods and Cones
Rods and Cones
Rods and Cones
Ganglion Cells
How they do what they do
Ganglion cells receive chemical messages from retinal interneurons which they turn into electrical messages to send to the brain visual centers.
This is done through induced membrane currents, when neurotransmitters start a response of either excitatory or inhibitory ganglion cells
Different Types of Ganglion Cell Types/Responses
ON-cell: respond with impulses to transient bursts of light during the whole time light is being used as a stimulus
OFF-cell: respond with impulses when light is turned off, for the whole time there is no light
Receptive Field
Color Selective Ganglion Cells
• Red ON/Green OFF• Red OFF/Green ON• Green ON/Red OFF• Green OFF/Red ON
Ganglion Cells
Ganglion Cells
Questions• When we are in a pitch black room, and then turn the lights on,
what part of our eye makes our eyes squint? Which part in our eye is the most sensitive to light?
• Is there a way to perceive the blind spot on the retina, or does our brain fill it in with perceptions from the other eye? How big is this blind spot?
• Does the thickness of the central retina contribute to why it does not show as much of the outside world as the peripheral retina?
• Why are the cells in the sensory layer of the retina arranged the way they are? Wouldn't it make more sense to have the rods and cones be closest to the lens since having the light pass through the ganglion and bipolar cells would scatter the light, decreasing the quality of images we see?
Questions
invertebrates vertebrates