the visual system. figure 6.1 a cross-sectional view of the human eye klein/thorne: biological...
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Figure 6.1 A cross-sectional view of the human eyeKlein/Thorne: Biological Psychology© 2007 by Worth Publishers
Vision = Perception of Light
• Light– Particles– Waves
• To humans, light = waves between 380-760 nanometers long
• Other wavelengths are visible to other animals
Figure 6.9 The electromagnetic spectrumKlein/Thorne: Biological Psychology© 2007 by Worth Publishers
Figure 6.3 Cellular organization of the retinaKlein/Thorne: Biological Psychology© 2007 by Worth Publishers
The Retina
Figure 6.4 The convergence of rods and cones onto ganglion cellsKlein/Thorne: Biological Psychology© 2007 by Worth Publishers
Rods and Cones
Cones and Rods
RODS• Helps you see in the
dark (more sensitive to light)
• Not good for seeing color
• Not good for seeing details
CONES• Most active when
there is a lot of light• Helps you see color• Helps you see fine
details
Figure 6.1 A cross-sectional view of the human eyeKlein/Thorne: Biological Psychology© 2007 by Worth Publishers
Fovea: Super sharp vision
Primary Visual Cortex
• Also known as the striate cortex• First stage of processing for visual information
Blindsight
• Damage to occipital lobe
• Person is able to respond to an object even though not consciously aware of seeing it
• Most often associated with object that is moving
The Case of D.B.
• Right occipital lobe removed• Things that are in left visual field are never
perceived• Therefore, D.B. had no awareness of seeing
things in left visual field• But…
– Could reach for things in left visual field– Could differentiate vertical line from horizontal or
diagonal line– Could differentiate letters “X” and “O”
Alternative explanation
Dorsal stream• Where
• Control of behavior
Ventral stream• What
• Conscious perception
Visual Agnosia
• Cannot name an object they see
• But can identify object if presented in a different mode (e.g., touch)
• Can see features of object but cannot integrate
Young-HelmholtzTrichromatic Theory
• Three different types of color receptors• Each type is sensitive to different color
– Red– Green– Blue or violet– Fig. 6.26
Young-HelmholtzTrichromatic Theory
• The color that you see is the result of a mixture of activity of each type of color receptor• E.g., yellow = activation of green and red fibers
• Research suggests that there are in foact three types of cones
Hering’s Opponent Process Theory
• Perception of color is based on pairs of complementary colors
• Red-Green, Yellow-Blue, Black-White
• For example: cells signal the color red by being hyperpolarized, and signal green by being depolarized
Hering’s Opponent Process Theory
• Perception of color is based on pairs of complementary colors
• Red-Green, Yellow-Blue, Black-White
• For example: cells signal the color red by being hyperpolarized, and signal green by being depolarized
Opponent Process Theory
• Research has also found support for opponent process theory: – E.g., there are cells that are activated by red
and inhibited by green, and vice ersa