From https://testbankgo.eu/p/Test-Bank-for-Sensation-and-Perception-9th-Edition-by-Goldstein
CHAPTER 2: THE BEGINNINGS OF PERCEPTION
Chapter Outline
I. Preview Questions
II. Starting at the Beginning
III. Light and Focusing
A. Light: The Stimulus for Vision
1. Electromagnetic spectrum
2. Wavelength and visible light
3. Photons
B. The Eye
1. Pupil
2. Cornea
3. Lens
4. Retina
5. Rods and cones
6. Optic nerve
C. Light is Focused by the Eye
1. Light waves bent by cornea and lens
2. Accommodation increases lens focusing power
a. Demonstration: Becoming aware of what is in focus
b. Accommodation and the near point
D. Loss of Accommodation with Increasing Age
1. Presbyopia
2. Solutions
E. Myopia (Nearsightedness)
1. Refractive and axial myopia
2. Solutions
a. Glasses and contact lenses
b. LASIK surgery
F. Hyperopia (Farsightedness)
IV. Receptors and Perception
A. Transforming Light Energy into Electrical Energy
1. Transduction begins at the receptors
a. Role of the outer segment for rod transduction
i. Opsin and retinal
b. Isomerization results in electrical signal
i. Psychophysical evidence (Hecht et al, 1942)
ii. Physiological evidence (Enzyme cascade)
B. Adapting to the Dark
1. Distribution of rods and cones
a. Macular degeneration
b. Retinitis pigmentosa
c. Blind spot
i. Demonstration: Becoming aware of the blind spot
ii. Demonstration: Filling in the blind spot
2. Measuring the dark adaptation curve
a. Method: Measuring the dark adaptation curve
3. Overall dark adaptation curve
4. “Mythbusters” test why pirates wore eyepatches
5. Measuring cone adaptation
6. Measuring rod adaptation
a. Rod monochromats
b. Rod-cone break
7. Visual pigment regeneration
a. Retinal and opsin rejoin
b. Rushton: Time measurement of regeneration
c. Detached retina shows importance of pigment regeneration
C. Spectral Sensitivity
1. Spectral sensitivity curves
2. Method: Measuring a spectral sensitivity curve
a. Rods most sensitive to 500 nm
b. Cones most sensitive to 560 nm
c. Perceptual consequence: Purkinje shift
3. Rod and cone absorption spectra
a. Explains difference between rod and cone curves
b. Evidence for three types of cones
V. “Test Yourself 2.1"
VI. Electrical Signals in Neurons
A. Structure of Neurons
1. Cell body
2. Dendrites
3. Axon
4. Illustrated example of an action potential
B. Recording Electrical Signals in Neurons
1. Method: The setup for recording from a single neuron
C. Basic Properties of Action Potentials
1. Propagated response
2. Stimulus intensity affects rate of firing
3. Refractory periods and rate of firing
4. Spontaneous activity
D. Chemical Basis of Action Potentials
1. The role of ions
2. The role of permeability
3. Phases of the action potential
4. The role of the sodium-potassium pump
E. Transmitting Information Across a Gap
1. Synapse
2. Neurotransmitters
3. Response at the receptor site
a. Excitation/depolarization
b. Inhibition/hyperpolarization
VII. Neural Convergence and Perception
A. Retinal anatomy
1. Receptors
2. Bipolar cells
3. Ganglion cells
4. Horizontal and amacrine cells
5. Neural convergence
6. Differences between rod and cone convergence
a. Signals from rods converge more than signals from cones
b. Many foveal cones have no convergence
B. Convergence Causes the Rods to Be More Sensitive Than the Cones
1. Illustrated example of rod convergence and increased sensitivity
2. Illustrated example of cone “private lines” and decreased sensitivity
C. Lack of Convergence Causes the Cones to Have Better Acuity Than Rods
1. Visual acuity – ability to see details
2. Demonstration: Foveal versus peripheral acuity
VIII. Something to Consider: Early Events are Powerful
A. Hubble Space Telescope Faulty Lens and “Eyeglasses”
B. Electromagnetic Energy and Visual Pigments Affect Vision
IX. Developmental Dimension: Infant Visual Acuity
A. Method: Preferential Looking
B. Infant Perception of Details
C. Rod and Cone Development
X. “Test Yourself 2.2”
XI. Think About It Exercises
XII. Key Terms
XIII. Media Resources: Virtual Lab/Companion Website
Learning Objectives
At the end of the chapter, the student should be able to:
1. Discuss how the electromagnetic spectrum is related to vision.
2. Describe how the cornea and lens focus the image on the retina.
3. Discuss why the near point is used as a measure of presbyopia.
4. State the difference between myopia and hyperopia, and treatments for both.
5. Describe the role of visual pigments in transduction.
6. Describe the method for measuring dark adaptation, and the overall results.
7. Discuss the differences between the distribution of the rods and the cones.
8. Name two visual conditions that differentially affect the rods and the cones
9. Explain why the “blind spot” exists, and why we are not usually aware of it.
10. Describe the method for isolating the rod and cone components of the dark adaptation curve, and the results for each.
11. Explain how visual pigment regeneration is related to dark adaptation.
12. Describe the difference in spectral sensitivity curves between rods and cones.
13. Define the Purkinje shift, and discuss how spectral sensitivity curves explain this phenomenon.
14. Identify the key components of neurons.
15. Describe the method involved in recording from a single neuron.
16. Define propagated response, and discuss how this is related to measuring activity in a single neuron.
17. Understand how the “refractory period” and “spontaneous activity” are important concepts in understanding the action potential.
18. Describe how electrical signals in a neuron are created, using the terms “ions,” “resting potential,” “action potential,” “permeability” and “selective permeability.”
19. Describe the process of synaptic transmission.
20. Discuss the difference between excitatory transmitters and inhibitory transmitters.
21. Differentiate depolarization and hyperpolarization.
22. Discuss why inhibition exists.
23. Describe what convergence is, and the difference in convergence between the rods and cones.
24. Explain why convergence results in greater sensitivity.
25. Define visual acuity.
26. Identify the difference in acuity between foveal and peripheral vision.
27. Explain why the lack of cone convergence results in greater acuity.
28. Discuss the challenges to testing infant perception.
29. Describe the methods used to test infant visual acuity.
30. Discuss how visual acuity develops over the first year of life.
Chapter Overview/ Summary
Chapter 2 begins with a discussion of the early stages of vision, specifically, how visible light is transformed by the major structures of the eye and receptors. Visible light (400 nm to 700 nm) is structured by the environment and reflected into the eye. The cornea and the lens focus the image on the retina. The lens accomplishes this by the process of accommodation, increasing the focusing power of the lens when viewing near objects. As we age, accommodation becomes more difficult, a condition called presbyopia. Two additional vision problems, myopia and and hyperopia, are described. After the visual image reaches the retina, transduction is accomplished by rods and cones. Exactly how transduction occurs in the rods and cones is then summarized. The visual pigment molecules are composed of opsin and retinal. The retinal reacts to light, by changing shape (a process called isomerization), which results in transduction. Physiological studies showed that isomerizing one visual pigment molecule results in the enzyme cascade, causing a sequence of chemical reactions within the receptor. The role of photopigments in the receptors are then discussed. The rods and cones are different in several ways: their shape, the location of each type on the retina, and overall number of each in the human eye. As rods and cones have distinct functions, they also can be associated with different disorders in vision: macular degeneration is a condition that destroys foveal cones; and retinitis pigmentosa primarily destroys the peripheral rods. Where there are no receptors (where the optic nerve leaves the eye), a blind spot exists. Rods and cones also differ in their adaptation to the dark, achieving maximum sensitivity at different times. Rushton showed that these times correspond to the time needed for pigment regeneration. Spectral sensitivity is also dependent on characteristics of the visual pigment, specifically, the absorption spectrum. A demonstration of the difference in spectral sensitivity for rods and cones is the Purkinje shift – enhanced perctption of short wavelengths during dark adaptation. After transduction, visual information is represented via an electrical signal. The electrical signal begins at the receptor and travels through the nerve to the brain where it synapses with neurons. The major parts of a neuron are listed, and the receptors are discussed as a specific type of neuron. The role of microelectrodes in recording neural activity is described. The details of how electrical signals are transmitted are discussed next. Four basic properties of action potentials are discussed: (1) the action potential is a propagated response; (2) changes in stimulus intensity increases rate of firing, not the size of the action potential; (3) refractory periods occur, providing an upper limit to firing rate; and (4) neurons have spontaneous activity, even when no stimuli are presented. A detailed discussion of the action potential follows including the role of sodium, chlorine, and potassium ions in the conduction of the electric signal. The values of the resting potential and how these change during the action potential are provided, as well as the role of permeability and selective permeability in the process. Communication between neurons occurs at the synapse: neurotransmitters are released across the synapse, and taken into the receptor sites. The change in the voltage of the postsynaptic neuron depends on the amount of excitation and inhibition it receives from the presynaptic neurons. Goldstein then describes differences in the transfer of information from rods and cones. He begins with the concept of convergence, then demonstrates the resultant trade-off between sensitivity and acuity. Convergence (as occurs with the rods) leads to greater sensitivity, but decreased acuity. “Direct lines” (as occurs with the foveal cones) leads to decreased sensitivity, but greater acuity. The final portion of the chapter details the challenges, methods, and results of research on infant perceptual development. Testing infant perceptual capabilities can be difficult as infants are non-verbal and because they act like infants. Therefore, methods like preferential looking (PL) and visual evoked potentials have been devised to assess infant visual capacities. Using these techniques, it has been determined that acuity progresses from about 20/400 - 20/600 at 1 month to full acuity after 1 year. The major reason for this is that the retinal cones and cortical cells have to develop. Contrast sensitivity functions, in which contrast is used to determine the sensitivity to seeing gratings, show that sensitivity to higher frequencies develop over the first three months, so fine details are only perceived from after 3 to 6 months.
Demonstrations, Activities, and Lecture Topics
(1) Classroom Pinhole Camera: Prull and Banks (2005) have developed an outstanding demonstration to teach about the functioning of the eye. They created a “classroom-sized pinhole camera” to demonstrate pupil functioning, image inversion, and focusing (including myopia and hyperopia). Details can be found at:
Prull, M. W., & Banks, W. P. (2005). Seeing the light: A classroom-sized pinhole
camera demonstration for teaching vision. Teaching of Psychology, 32, 103-106.
(2) Online Tests for Visual Disorders: Free online eye “exams” for macular degeneration, myopia, and hypermyopia can be found online at the Optometric Eye Site. The St. Luke’s Cataract and Laser Institute website has a page entitled “Eye Q” which also contains the Amsler grid (can be printed) and information. For the test, the student would cover one eye and look at the fixation point. While doing this, they should see if the lines appear wavy or if portions of the grid are missing; either result would be a potential indicator of an abnormality.
(3) Visual Disorders: The topic of visual disorders always leads to numerous questions from students. Be prepared for questions about LASIK and other surgical treatments, macular degeneration, and astigmatism. The websites listed below contain information, photos, and animations on numerous disorders.
(4) Eye Models: For instructors with larger budgets, Denoyer-Geppert Science Company offers a range of eye models that provide students with “hands-on experience.” There is a less-expensive student version, and a more detailed and expensive “Giant Five-Part Eyeball.” “Rubin’s Eye and Vision Lab” also may be a good investment, in which you can change lenses to demonstrate focusing problems. These can be ordered from the website.
(5) Video Suggestion: Denoyer-Geppert also has a video series – “The Special Senses” – that covers some information presented in Chapter 2. The video reviews each sensory receptor (vision, hearing, smell, taste). For vision, there is discussion of the eyeball and the process of refraction.
(6) Interactive Class Demonstrations: There have been at least three articles that have addressed how to get the class directly and actively involved in simulating neural functioning. Some have been used for introductory psychology and physiological psychology, but certainly would be appropriate for this chapter. Here are the references for these three:
Bockoven, J. (2004). The pedagogical toolbox: Computer-generated visual displays, classroom demonstration, and lecture. Psychological Reports, 94, 967-975.
Hamilton, S. B., & Knox, T. A. (1985) The collossal neuron: Acting out physiological psychology. Teaching of Psychology, 12(3), 153-156.
Reardon, R.R., Durso, F.T., & Wilson, D.A.. (1994). Neural coding and synaptic transmission: Participation exercises for introductory psychology. Teaching of Psychology, 21(2), 96-99.
(7) 4) Evolution and Synapses: An interdisciplinary approach to neural functioning was addressed in a 2008 New York Times article on the relationship between evolution and synapse formation. The article is entitled, “Brainpower may lie in the complexity of synapses”.
(8) Preferential Looking and Confounds: A research method issue of experimenter effects can be highlighted by research involving the preferential looking technique. Goren, Sarty, and Wu (1975) reported that newborns preferred looking at “scrambled faces” than “unscrambled faces.” Maurer and Young (1983) were skeptical about the results, and replicated the study, with two important differences: (1) they put the infant in a baby seat, instead of the experimeter’s lap; and (2) made sure that the experimenter could not see the stimulus. These changes eliminated the preference for the scrambled faces. The implication is that the experimenters in the first study may have unintentionally influenced the infant’s looking behavior. The bottom line is that care must be taken in using these techniques when testing infants.