4.2 Pgs. 143-171 Flashcards
List the physical properties of light and the
aspects of visual perception that these properties influence. (p. 143)
Physical Properties of Light —
Form of electromagnetic radiation that travels as a wave.
1.) Amplitude —
Wave height
2.) Wavelength —
Distance between peaks
3.) Purity
How varied the mix of wavelengths is
Aspects of visual perception that these perperties influence –
- ) Amplitude — Brightness
- ) Wavelength — Color
- ) Purity — Saturation
Figure 4.6, 4.7
Describe the path of a ray of light as it travels through the various structures of the eye to the point of most-effective focus.
Describe nearsightedness and
farsightedness. (pp. 143-147)
Describe the path of a ray of light as it travels through the various structures of the eye to the point of most-effective focus.
Cornea — “window” lets light in.
Irismuscle that modulates how much light is allowed into the eye
pupil — the opening in the middle of the iris that helps regulate light
Lens — focuses the light into an upside down image on the retina
Close — Fat
Far — Flat
Retina — part of the central nervous system that contains rods and cones which are light receptor cells that detect light. Thh uh e retina also processes the image.
Rods -
Peripheral, Needs less light, can’t see color, less sharp image.
Cones —
In the middle of the eye. The fovea is the the spot of the eye with only cones. needs more light, can see color, sharper image.
Nearsightedness —
Can see up close but not far away.
Farsightedness. (pp. 143-147) —
Can see distance but not up close.
Explain the function of rods and
cones.
Describe their distribution in the retina. (pp. 146-147)
Rods --
Can’t see color, better than cones in low light, less sharp image
Cones --
Can see color, worse than rods in low light, sharper image.
Distribution in the Retina --
Rods - periphery
Cones - center; fovea
Describe the role of rods and cones
in adaptation to darkness and light. (p. 147)
Dark Adaptation — the process in which eyes become more sensitive to light in low illumination.
The Role of Rods and Cones in adaptation to darkness and light –
Cones adapt to darkness quickly but hit their limit quickly.
Rods adapt to darkness slower but, over time, will be capable of much better sight in dim lighting.
Describe the processing of visual information within the retina,
with special focus on the concepts of
receptive fieldsand
lateral antagonism. (p. 148)
The Processing of Visual Information within the retina –
light from the lense is absorbed by the retina. The light is detected by a cells receptive field. In circular fields with a center-surround arrangement, light hitting the center of the field has an excitatory effect and light hitting the surround of the field has an inhibitory effect, a concept known as lateral antagonism. Thus, the retinal cell’s receptive field uses lateral antagonism to highlight contrast in order to perceive useful information.
Describe the routing of signals from the eye to the brain. (p. 149) 4.2.4 b
The Routing of Signals from the Eye to the Brain – figure 4.14
axons from the optic disk, forming the optic nerves, travel to the optic chiasm — the point at which the optic nerves from the inside half of each eye cross over and then project to the opposite half of the brain. After reaching t ugh e optic chiasm, the optic nerve fibers diverge along two pathways:
1.) The first pathway projects into the thalamus. Here, The visual signals are processed by the Lateral geniculate nucleus (LGN) and then distributed to areas in the occipital lobe that make up the primary visual cortex.
1.) Based on which layer of LGN they synapse in, visual information travels along two more subdivisions. The first is called the magnocellular channel. The magnocellular channel processes brightness.
2.) the Parvocellular channel processes color.
These channels engage in parallel processing — simultaneously extracting different information from the same input.
- ) The second pathway branches to the midbrain. It goes to an area in the midbrain called the superior colliculus before traveling to the thalamus and continuing as if path 1.
- 2nd path for coordinating sensory input with visual input.
Describe Hubel and Weisel’s work on information processing in the visual cortex? (pp. 149-152) 4.2.4 C
Hubel and Weisel –
1962, 1963
Nobel Prize winning research demonstrated that there were various types of specialized cells in the primary visual cortex that respond to different stimuli. They did this by measuring the rate at which action potentials were fired while shown various stimuli. The cell have been characterized as feature detectors — neurons that respond selectively to very specific features of more complex stimuli.
What is visual agnosia?
How may it be explained?
What is prosopagnosia? (p. 152)
Visual Agnosia –
Inability to recognize objects.
How it may be explained:
Damage somewhere along the visual pathway that handles information.
Prosopagnosia –
Inability to recognize familiar faces.
Describe the McCollough effect. (pp. 152-153)
The McCollough effect –
Figure 4.17
A well-know after-image phenomenon that differs from other after image phenomenon because it is contingent on not color and pattern.
Definesubtractive colour mixing
and
additive colour mixing
, and give examples of each. (pp. 153-154)
Subtractive Color Mixing –
Example –
Additive Color Mixing –
Example –
Describe the trichromatic and opponent process theories of colour vision.
What evidence indicates that both theories are required to explain colour vision?
What are complimentary colours, and
why are these discussed when the opponent-process theory of colour vision is discussed in the textbook? (pp. 154-156)
Trichromatic and Opponent Process Theories –
Evidence indicating both theories are required to explain color vision –
Complementary Colors –
These are discuused when the opponent-process theory of color vision is discussed in the textbook because
Definecolour-blindness.
Describe the effects of gender on colour-blindness.
Are most people who are colour-blind completely blind to differences in colours?
Explain. (p. 155)
Color-Blindenss -- Effects of Gender on Color-Blindness -- Are poeple who are colorblind completely blind to differences in colors? --
Do colours have an effect on our behaviour?
Why?
What effect does red clothing have when a woman wears it?
What effect does a red moving object produce? (pp. 156-157)
Do colors have an effect on our behavior? Why? When a woman wears red clothing, it has the effect of A red moving object has the effect of
What is a reversible figure?
What is a perceptual set?
What is inattentional blindness? (pp. 157-159)
Reversible Figure -- Perceptual Set -- Inattentional Blindness --
Describe the process of feature analysis as it relates to the perception of shape and form.
Definebottom-up processingand
top-down processing.
Definesubjective contours. (pp. 159-160)
The Proces of Feature Analysis: Bottom-up Processing -- Top-Down Processing -- Subjective Contours --
