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Chapter 6: Vision 6.1 Multiple Choice 1) After suffering brain damage ________, Mrs. R was unable to ________. A) from a stroke; recognize common objects B) from a bullet wound to the brain; speak fluent French. C) to the right hemisphere; carry on a social conversation. D) during a car accident; make movements with her right hand. E) during a bar fight; work on a farm. Answer: A 2) An implication of the perceptual difficulties suffered by Mrs. R is that A) consciousness is a general property of the brain. B) impaired motor function is usually noted with impaired sensory function. C) words are not perceived as objects. D) the rostral portions of the brain are organized for sensory function. E) the caudal portions of the brain are organized for motor function. Answer: C Rationale: Sensory receptors are specialized for the detection of physical stimuli. 3) Sensory receptors are specialized for the A) detection of physical stimuli. B) induction of movement of a limb. C) detection of specific chemicals released from other neurons. D) detection of internal—but not external—stimuli. E) All of the above are correct. Answer: A 4) A sensory receptor is a variant of a A) neuron B) axon terminal C) stem cell D) motor neuron E) muscle fiber Answer: A 5) Which of the following is true of the process of sensory transduction? A) Receptors show action potentials to external stimuli. B) The intensity of an external stimulus is related to the firing rate of the receptor. C) Receptors convert an external energy into graded changes in receptor membrane potential. D) Most receptors show an action potential when stimulated with an external stimulus. E) Transduction refers to the speed at which a sensory message travels toward the brain. Answer: C Rationale: Sensory receptors convert an external energy into graded changes in receptor membrane potential. 6) Which of the following is true of the process of sensory transduction? A) Transduction refers to the speed at which a sensory message travels toward the brain. B) An external energy induces changes in muscle fiber contractions. C) The intensity of an external stimulus is related to the firing rate of the receptor. D) Most receptors show an action potential when stimulated with an external stimulus. E) Sensory cell receptor potentials directly control the release of neurotransmitters. Answer: E Rationale: Sensory cell receptor potentials directly control the release of neurotransmitters. 7) The physical stimulus for human vision is A) infrared radiation with a wavelength between 760 and 790 nanometers. B) all wavelengths of light. C) ultraviolet radiation with a wavelength of 180–350 nanometers. D) electromagnetic radiation with a wavelength between 380 and 760 nanometers. E) electromagnetic radiation with a wavelength between 100 and 400 meters. Answer: D 8) Human can detect wavelengths of light between the ________ rays and the ________ rays. A) X-; gamma B) X-; ultraviolet C) gamma; ultraviolet D) ultraviolet; infrared E) infrared; radar Answer: D 9) A human can detect wavelengths of light that are between ________ and ________ nm. A) 100; 200 B) 100; 380 C) 200; 380 D) 380; 760 E) 760; 980 Answer: D 10) The perceptual color attribute of ________ corresponds to that of light wavelength. A) saturation B) brightness C) hue D) intensity E) contrast Answer: C 11) The intensity of a light stimulus corresponds to A) brightness. B) saturation. C) hue. D) color. E) threshold. Answer: A 12) A normal human exposed to a light stimulus that contains an equal number of all wavelengths will report a perception of A) purple. B) a rainbow of colors. C) black. D) white. E) a fuzzy set of alternating black and white bars. Answer: D Rationale: A normal human exposed to a light stimulus that contains an equal number of all wavelengths will report a perception of white. 13) Variation in the ________ of a light will result in variation in the perception of ________. A) wavelength; saturation B) saturation; brightness C) wavelength; brightness D) intensity; purity E) wavelength; hue Answer: E 14) A light stimulus that is composed of only one wavelength would be said to exhibit A) reduced saturation. B) decreased brightness. C) hue. D) purity. E) reduced contrast. Answer: D 15) Purity is to wavelength saturation as intensity is to A) hue. B) brightness. C) fuzziness. D) apparent hue. E) spatial frequency. Answer: B Rationale: Purity is to wavelength saturation as intensity is to brightness. 16) Hue is to wavelength as saturation is to A) brightness. B) intensity. C) concentration. D) purity. E) threshold. Answer: D Rationale: Hue is to wavelength as saturation is to purity. 17) The bony cavities of the skull that contain the eyes are the A) orbits. B) optic disks. C) optic sinuses. D) conjunctivae. E) optic ossicles. Answer: A 18) The human eye is composed of a number of layers of tissue. The outermost layer is the A) cornea. B) sclera. C) lens. D) retina. E) vitreous humor. Answer: B 19) A tear in the muscles that connect the orbits with the sclera would be expected to A) reduce the diameter of the pupil. B) impair movements of an eye. C) change the rate of eye blinking. D) impair the ability of a person to blink to an air puff. E) dilate the pupil. Answer: B Rationale: The membrane that lines the eyelids and attaches to the eye around the cornea is called the conjunctiva. 20) The membrane that lines the eyelids and attaches to the eye around the cornea is called the A) sclera. B) vitreous humor. C) conjunctiva. D) cornea. E) iris. Answer: C 21) The amount of light entering the eye is regulated by the size of the A) conjunctiva. B) lens. C) sclera. D) pupil. E) optic orbits. Answer: D 22) The function of the pupil is to A) control the amount of light that enters the eye. B) control eye movements as one tracks a moving object. C) focus light onto the retina. D) invert the visual image on the retina. E) amplify the intensity of light that is passed through the vitreous humor. Answer: A Rationale: The function of the pupil is to control the amount of light that enters the eye. 23) The function of the lens is to A) control the amount of light that enters the eye. B) control eye movements as one tracks a moving object. C) focus light onto the retina. D) invert the visual image on the retina. E) amplify the intensity of light that is passed through the vitreous humor. Answer: C Rationale: The function of the lens is to focus light onto the retina. 24) The process of accommodation involves A) the hardening of the lens as one ages. B) the contraction of the ciliary muscles to constrict the pupil. C) the contraction of the ciliary muscles to dilate the pupil. D) the lens becoming smaller as one ages. E) changes in the shape of the lens to focus on near or distant objects. Answer: E 25) Collectively, the rods and cones are known as A) photoreceptors. B) optotectors. C) the fovea. D) ganglion cells. E) vitreous humor. Answer: A 26) The reason for a "blind spot" in the visual field is that A) rods are less sensitive to light than are cones. B) blood vessels collect together and enter the eye at the blind spot. C) the lens cannot focus all of the visual field onto the retina. D) retinal cells die with age and overuse, resulting in blind spots. E) there are no photoreceptors in the retina where the axons exit the eye. Answer: E 27) Rods are to cones as A) color vision is to night vision. B) acuity in the dark is to acuity in the day. C) excellent acuity is to poor acuity. D) fovea is to periphery. E) brightness is to purity. Answer: B Rationale: Rods are to cones as acuity in the dark is to acuity in the day. 28) A key function of rod photoreceptors is to A) detect colors. B) detect fine details in the visual field. C) detect light under low levels of illumination. D) detect light under high levels of illumination. E) detect the texture of the visual scene. Answer: C Rationale: A key function of rod photoreceptors is to detect light under low levels of illumination. 29) A disease that attacks the photoreceptors of the retinal periphery would be expected to A) impair night vision. B) disrupt color vision. C) impair eye movements. D) impair vision for fine detail. E) diminish our ability to perceive depth. Answer: A Rationale: A disease that attacks the photoreceptors of the retinal periphery would be expected to impair night vision. 30) The optic disk is the location on the retina A) where the cones are most densely packed. B) where the rods are most densely packed. C) that has the best visual acuity. D) where axons leave the eye and join the optic nerve. E) at which neural signals begin to diverge laterally. Answer: D 31) A disease that attacks the photoreceptors of the fovea would be expected to A) impair night vision. B) disrupt color vision. C) impair eye movements. D) impair vision for detection of movement. E) produce blurry images. Answer: B Rationale: A disease that attacks the photoreceptors of the fovea would be expected to disrupt color vision. 32) A unique feature of the retinal circuitry is that A) rods send signals through cones which then activate the ganglion cells. B) light must pass through the circuitry in order to stimulate the photoreceptors. C) the rods are packed together at the center of the retina. D) there are more cones than rods in the retina. E) photoreceptors do not influence the activity of surrounding nerve cells. Answer: B Rationale: A unique feature of the retinal circuitry is that light must pass through the circuitry in order to stimulate the photoreceptors. 33) The optic nerve is formed by axons that arise from the ________ retinal cells. A) ganglion B) photoreceptor C) horizontal D) amacrine E) bipolar Answer: A 34) The human retina contains about ________ rods and about ________ cones. A) 60 million; 3 million B) 9 million; 120 million C) 32 million; 320 million D) 120 million; 6 million E) 160 million; 3 million Answer: D 35) The ________ cell is interposed in the pathway between the photoreceptors and the ganglion cells. A) multipolar B) horizontal C) bipolar D) amacrine E) unipolar Answer: C 36) Lateral interactions between adjacent photoreceptors, bipolar cells, and ganglion cells are carried out by the ________ cells. A) amacrine B) ventral C) multipolar D) unipolar E) A and B are correct. Answer: E 37) Photopigments are located within the A) lamellae membranes of the outer segments. B) inner membrane of bipolar cells. C) ganglion cells. D) amacrine cells. E) lamellae membranes of the inner segments. Answer: A 38) When a photopigment is exposed to light, the pigment A) turns a rosy pink. B) is released from the axon terminal. C) degrades into an opsin and a retinal. D) joins an opsin with a retinal. E) undergoes a change in electrical charge. Answer: C 39) Photopigments are molecules that consist of A) two peptides and a sugar molecule. B) an opsin and a retinal. C) a steroid ring. D) two fatty acid chains. E) a carbon ring and a phenyl ring. Answer: B 40) Visual information from the retina is carried by ________ to the ________. A) short axon fibers; optic chiasm B) ganglion cell axons; thalamic medial geniculate nucleus C) axons from bipolar cells; thalamic medial geniculate nucleus D) ganglion cell axons; thalamic dorsal lateral geniculate nucleus E) ganglion cell axons; striate cortex Answer: D 41) Which of the following is true of the thalamic dorsal lateral geniculate nucleus (LGN)? A) Each layer of the LGN receives information from both eyes. B) The LGN is comprised of six similar layers. C) The inner four layers of the LGN are termed the parvocellular layers. D) The outer four layers of the LGN are termed the magnocellular layers. E) The cell bodies of the inner two layers of the LGN are larger than those of the outer four layers. Answer: E 42) The parvocellular and magnocellular layers of the dorsal lateral geniculate nucleus A) may belong to different visual systems. B) analyze the same kind of information from the visual field. C) are connected to the nasal and temporal halves of the retina, respectively. D) receive input from the contralateral and ipsilateral halves of the visual field, respectively. E) analyze acuity and spatial frequency, respectively. Answer: A 43) Three distinct sets of layers in the lateral geniculate nucleus first receive input from the A) bipolar cells. B) horizontal cells. C) ganglion cells. D) photoreceptors. E) amacrine cells. Answer: C 44) Another term for the primary visual cortex is A) area 51. B) the striate cortex. C) the opercular cortex. D) the calcarine cortex. E) the chiasmic cortex. Answer: B 45) The manner in which visual information is carried from the retina to the cortex results in A) information from the temporal ganglion cells projecting to the opposite hemisphere. B) information from the nasal ganglion cells projecting to the ipsilateral hemisphere. C) information from one side of the visual field being transmitted to the opposite hemisphere. D) visual information remaining on the same side of the brain from retina to cortex. E) information from each retina directly reaching both sides of the visual cortex. Answer: C Rationale: The manner in which visual information is carried from the retina to the cortex results in information from one side of the visual field being transmitted to the opposite hemisphere. 46) The ________ pathways are important for the synchronization of locomotor activity to the light-dark cycle in rats. A) retino-geniculate-cortical B) retino-spinal C) retino-pretectal D) retino-hypothalamic E) retino-cerebellar pathway Answer: D 47) Select the correct sequence for processing of information in the primary visual pathway. A) retina → dorsal lateral geniculate (DLG) → striate cortex B) retina → striate cortex → extrastriate cortex → inferior temporal cortex C) retina → DLG → inferior temporal cortex → amygdala D) DLG → retina → striate cortex → primary visual cortex E) DLG → frontal cortex → amygdala → extrastriate cortex Answer: A 48) A microelectrode is inserted into a neuron within the primate visual system. Various stimuli are presented to the eyes and changes in firing rate are recorded from this visual system neuron. The part of the visual field to which a neuron responds is termed the A) magnocellular visual system. B) parvocellular visual system. C) striate response field. D) tuning curve. E) receptive field. Answer: E 49) Which of the following is an explanation for the higher acuity of the visual system at the fovea, relative to the periphery of the retina? A) A foveal ganglion cell may receive information from a single photoreceptor, whereas a peripheral ganglion cell may receive information from multiple photoreceptors. B) The fovea contains only rods which are directly connected to the ganglion cells. C) The foveal photoreceptor cells contain more photopigment per cell. D) Peripheral photoreceptors are more likely to be damaged by prolonged light exposure. E) Peripheral photoreceptors require greater activation in order to provoke a visual response. Answer: A Rationale: An explanation for the higher acuity of the visual system at the fovea, relative to the periphery of the retina is that a foveal ganglion cell may receive information from a single photoreceptor, whereas a peripheral ganglion cell may receive information from multiple photoreceptors. 50) Retinal ganglion cells of the "ON" type described by Kuffler A) fire randomly to light and dark conditions. B) record an excitatory burst of potentials to a light placed within a circular center. C) show suppressed numbers of potentials to a light placed within a circular center. D) show an increased number of potentials when a light was placed onto a ring surrounding the center. E) show a change in response rate to movement. Answer: B Rationale: Retinal ganglion cells of the "ON" type described by Kuffler record an excitatory burst of potentials to a light placed within a circular center. 51) The primate retina contains A) two photopigments. B) three photopigments. C) one type of cone and three types of rods. D) only cones. E) only rods. Answer: B 52) A selective advantage conferred by color vision is the A) ability to detect a dark spot moving on a white background. B) capacity to sense depth in the visual scene. C) ability to detect very faint lights in the distance. D) capacity to detect texture gradients in the visual scene. E) ability to distinguish ripe from unripe fruit. Answer: E Rationale: A selective advantage conferred by color vision is the ability to distinguish ripe from unripe fruit. 53) In ________, a combination of yellow and blue ________ will form the color green. A) color mixing; lights B) pigment mixing; lights C) the trichromatic theory; afterimages D) pigment mixing; pigments E) the opponent-process system; dyes Answer: D Rationale: In pigment mixing, a combination of yellow and blue pigments will form the color green. 54) People with the form of color blindness known as deuteranopia A) lack "red" cones. B) have poor visual acuity. C) have "red" cones filled with "green" photopigment. D) have "green" cones filled with "red" photopigment. E) have color pigments within their rods. Answer: D 55) Which of the following is true of most color-sensitive ganglion cells? A) The cells are not organized in a center-surround fashion until this information reaches the thalamus. B) The ganglion cells respond to pairs of primary colors such as red-green or blue-yellow. C) These ganglion cells receive information from certain rods in the periphery of the retina. D) These cells also code for the relative brightness of colors. E) Each is tuned to one of the 12 primary colors. Answer: B 56) The fact that we experience the color green after viewing a red object would be taken as support for the A) notion that the retina contains three types of photopigments. B) importance of color mixing in the visual system. C) opponent-process theory of color vision. D) idea that the visual system performs an algebraic summation of lights to generate a color perception. E) trichromatic theory of color vision. Answer: C Rationale: The fact that we experience the color green after viewing a red object would be taken as support for the opponent-process theory of color vision. 57) A person who suffers from protanopia would be said to A) have poor visual acuity. B) confuse yellow with blue. C) lack "blue" cones. D) have "red" cones filled with "green" photopigment. E) perceive a blue sky as green in color. Answer: D 58) Research by Hubel and colleagues indicate that neurons of the ________ show responses to ________ of the visual field. A) lateral geniculate nucleus; moving bars of light in the center B) retinal periphery; color stimuli C) striate cortex; points of light and darkness D) retina; points of light and darkness E) striate cortex; specific features Answer: E Rationale: Research by Hubel and colleagues indicate that neurons of the striate cortex show responses to specific features of the visual field. 59). Which of the following is true of striate cortex (ST)? A) ST is comprised of four layers. B) ST is located within the temporal lobe. C) ST is comprised of six layers. D) ST is comprised of axons but not cell bodies. E) ST is devoted to analysis of auditory information. Answer: C 60) A complex cell located within the striate cortex would be most activated by a A) line moving perpendicular to its orientation. B) stationary line placed at the edge of the field. C) dark, stationary circle. D) black dot that moved erratically around the visual field. E) set of fuzzy parallel lines of low spatial frequency. Answer: A 61) Imagine that you are looking at a bronze cast depicting the face of Mick Jagger and a second cast showing the face of Casper the Ghost. Which of the following statements would be true of the spatial frequencies represented in these casts? A) Mick's face contains mostly low-frequency elements. B) Mick's face contains many high-frequency elements. C) Casper's face would be an example of an image made fuzzy because it lacks low-frequency information. D) Casper's face contains much higher frequency information. E) Mick's wrinkles represent low-frequency features. Answer: B Rationale: Imagine that you are looking at a bronze cast depicting the face of Mick Jagger and a second cast showing the face of Casper the Ghost. Mick's face contains many high-frequency elements. 62) The perception of depth cue that is provided by input from both eyes is termed A) atmospheric haze. B) relative retinal size. C) perspective. D) stereopsis. E) color vision. Answer: D 63) Retinal disparity is necessary for A) depth perception. B) stereopsis. C) red-green color vision. D) brightness sensitivity. E) blue-yellow color vision. Answer: B 64) Cells located within the cytochrome oxidase blobs of striate cortex play a key role in A) color vision. B) pattern discrimination. C) line orientation. D) analyzing retinal disparity. E) producing depth perception. Answer: A 65) Which of the following is a binocular cue for depth perception? A) perspective B) relative retinal size C) retinal disparity D) relative apparent movement E) loss of detail due to atmospheric haze Answer: C 66) Information from the red and green ganglion cells is transmitted through the ________ layers of the LGN to the ________ of the striate cortex. A) magnocellular; cytochrome oxidase blob regions B) parvocellular; inter-blob regions C) magnocellular; inter-blob regions D) koniocellular; cytochrome oxidase blob regions E) parvocellular; cytochrome oxidase blob regions Answer: E 67) The neurons from the parvocellular and magnocellular layers of the primate lateral geniculate send their information to layer(s) ______ of the striate cortex. A) 1 B) 2A C) 3B D) 4C E) 5–6 Answer: D 68) The central region of a module of the primary visual cortex that is revealed by a stain for the mitochondrial enzyme cytochrome oxidase is termed a(n) A) extra-blob region. B) blob. C) ganglion cell. D) simple cell. E) complex unit. Answer: B 69) Most neurons between the blob regions of a striate cortex module are sensitive to all of the following EXCEPT A) retinal disparity. B) orientation. C) color. D) spatial frequency. E) movement. Answer: C 70) Imagine that a scientist has discovered a nerve toxin that selectively destroys the columns of neurons that lie within the blob regions of striate cortex modules. Which of the following would you expect to be most profoundly impaired by this toxin? A) movement sensitivity B) orientation sensitivity C) depth perception D) color vision E) texture perception Answer: D Rationale: Assuming that a nerve toxin can selectively destroy the columns of neurons that lie within the blob regions of striate cortex modules, one would expect color to be most profoundly impaired by this toxin. 71) The modules of primary visual cortex project their information mostly to A) the amygdala. B) the frontal cortex. C) the auditory association cortex. D) the primary motor cortex. E) the extrastriate cortex. Answer: E 72) In thinking of the pathways taken by visual information within the association cortex, the dorsal stream projects to the ________ and is involved in ________. A) temporal association cortex; object form B) parietal association cortex; the analysis of where an object is located in space C) primary motor cortex; object texture D) parietal association cortex; the analysis of object identity E) inferior temporal cortex; the analysis of where an object is located in space Answer: B 73) In thinking of the pathways taken by visual information within the association cortex, the ventral stream projects to the ________ and is involved in ________. A) parietal association cortex; the analysis of "where" an object is located in space B) temporal association cortex; object color C) primary motor cortex; object texture D) parietal association cortex; the analysis of object identity E) inferior temporal cortex; deciding on the "what" of an object Answer: E 74) Which of the following is NOT a function of the human magnocellular visual system? A) movement perception B) perception of large objects C) brightness perception D) color vision E) perception of retinal disparity Answer: D 75) Tasks that involve identification of an object would be expected to activate neurons of the ________, while tasks that identify the location of an object would activate the ________. A) area V5; area V1 B) frontal cortex; parietal cortex C) ventral stream; dorsal stream D) parietal cortex; frontal cortex E) dorsal stream; ventral stream Answer: C Rationale: Tasks that involve identification of an object would be expected to activate neurons of the ventral stream, while tasks that identify the location of an object would activate the dorsal stream. 76) Area V4 of primate extrastriate cortex is critical for the analysis of A) color. B) color constancy. C) form. D) object texture. E) movement. Answer: B 77) The neurons of area ______ are important for the analysis of color. A) TEO B) V8 C) V7 D) MT+ E) V4 Answer: E 78) Area V6 of human extrastriate cortex is critical for the analysis of A) color and the memory of color. B) depth perception. C) movement. D) object texture. E) form. Answer: A 79) Which of the following is true of achromatopsia? A) It is produced by damage to area V2 of medial frontal cortex. B) The blindness is complete for object form as well as object color. C) The condition impairs current color perception, but not color recall. D) It is produced by damage to area V8 of the visual association cortex. E) The condition improves depth perception. Answer: D Rationale: Achromatopsia is produced by damage to area V8 of the visual association cortex. 80) Cerebral achromatopsia refers to A) seeing the world as shades of one color. B) a symptom of Balint's syndrome. C) a loss of color vision. D) seeing the world as shades of red and green. E) a difficulty in scanning the visual scene. Answer: C 81) Neurons of the inferior temporal cortex respond best to A) moving spots. B) specific 3D objects. C) lines. D) coarse textures. E) sine wave gratings. Answer: B 82) The inability to perceive or identify a stimulus via a particular sensory modality is A) agnosia. B) prosopagnosia. C) insomnia. D) aphagia. E) amnesia. Answer: A Rationale: The inability to perceive or identify a stimulus via a particular sensory modality is termed agnosia. 83) Damage limited to the fusiform region of the right hemisphere would be expected to impair the recognition of A) movement of objects through space. B) fruits and vegetables. C) faces. D) object location. E) color. Answer: C Rationale: Damage limited to the fusiform region of the right hemisphere would be expected to impair the recognition of faces. 84) Prosopagnosia is A) an inability to distinguish colors. B) the inability to recognize a particular face. C) usually accompanied by achromatopsia. D) a difficulty in recognizing objects by texture cues. E) a problem in linking remote memories with new memories. Answer: B 85) Transcranial magnetic stimulation of the ______ will impair _______. A) extrastriate body area; recognition of body parts B) parahippocampal place area; perception of spatial maps C) lateral optic area; natural scene perception D) fusiform face area; body part recognition E) PPA; perception of spatial maps Answer: A Rationale: Transcranial magnetic stimulation of the extrastriate body area will impair recognition of body parts. 86) What brain region is most important for perception of movement in monkeys? A) Area V5 in the extrastriate cortex. B) The cells within blobs of the cortical modules. C) Area TEO in the inferior temporal cortex. D) Area TE in the inferior temporal cortex. E) Area V8 Answer: A 87) The analysis of complex visual perception as one moves through an environment is referred to as A) optic flow. B) motion parallax. C) motion from form. D) controlled flow. E) form from motion. Answer: A 88) Temporary inactivation of an area in the human cortex that is analogous to area V5 in the primate brain would be expected to A) improve facial recognition. B) impair perception of movement. C) alter color perception. D) impair facial recognition. E) impair object identification. Answer: B 89) According to Goodale, the key function of the dorsal visual stream is to A) recognize objects. B) integrate vision with language output. C) guide motor movements. D) integrate vision with audition. E) integrate the analysis of form and color. Answer: C Rationale: According to Goodale, the key function of the dorsal visual stream is to guide motor movements. 90) In the epilogue on case studies, Carlson argues that A) valid conclusions can only be drawn from groups of brain-damaged persons. B) brain modules can be proven to control individual behaviors. C) a case study involves the intensive study of disabilities noted in groups of people. D) brain damage is usually similar from case to case. E) certain case study results can be used to eliminate the role of a brain module in a specific behavior. Answer: E Rationale: In the epilogue on case studies, Carlson argues that certain case study results can be used to eliminate the role of a brain module in a specific behavior. 6.2 True-False 1) The visual disorder suffered by Mrs. R in the prologue is an example of visual agnosia. Answer: True 2) The wavelength of light determines the psychological dimension of hue. Answer: True 3) The fovea contains of an equal mixture of cones and rods. Answer: False 4) The primate retina contains 55 types of photoreceptors. Answer: True 5) The striate cortex refers to the primary visual cortex. Answer: True 6) There are fewer "blue" cones in the retina than "red" or "green" cones. Answer: True 7) The striate cortex is arranged in 6 major layers. Answer: True 8) A cell in the visual cortex that has a "complex" receptive field may serve as a movement detector. Answer: True 9) Sharp edges and fine detail contain low spatial frequencies. Answer: False 10) Neurons within the blob portion of the cortical modules are insensitive to color. Answer: False 11) Cells within a CO "blob" region of a module in striate cortex are sensitive to orientation, movement, and texture cues. Answer: False 12) The extrastriate cortex is also called the prestriate or circumstriate cortex. Answer: True 13) The parvocellular visual system receives information from "red" and "green" cones. Answer: True 14) The determination of the "what" of an object is a key function of the dorsal visual stream. Answer: False 15) People with visual agnosias have normal acuity, but are unable to recognize objects. Answer: True 16) Damage to the FFA impairs the recognition of facial features. Answer: True 17) Neurons in area V5 are sensitive to movement. Answer: True 18) TMS applied to area MT produces color blindness. Answer: False 19) Approximately 25% of human cerebral cortex is dedicated to the analysis of visual information. Answer: True 6.3 Short-Answer Essay 1) Explain what is involved in the process of sensory transduction. Answer: Physical stimuli such as light, sound pressure, or chemicals interact with specialized receptors in a sensory organ. These receptive neurons show graded changes in their membrane potentials in response to the occurrence of a physical stimulus. The transduction process in effect converts physical energy to a change in neuron electrical potential/action potentials. 2) Describe how the physical dimensions of light correspond to the psychological dimensions of light. Answer: Wavelength of light refers to the distance between successive light wave peaks and determines the hue (perceived color) of a light. The intensity of light corresponds to the psychological dimensions of brightness. Finally, purity refers to whether a light contains one or more wavelengths, and this corresponds to the dimension of color saturation. 3) Compare and contrast the visual functions of rods and cones. Answer: The retina of the eye contains the photoreceptors that transduce light. Rods are more common than are cones, which predominate within the central region of retina (the fovea). Color vision is mediated by cones. The ability to resolve fine detail is also a function of cones within the fovea. Rods can function in low light conditions. 4) Describe the primary visual pathway. Answer: Cells in the retina project through the optic chiasm to terminate in the dorsal lateral geniculate thalamic nucleus (LGN) and from there traverse to the striate cortex. 5) Explain the notion that neurons in striate cortex function as feature detectors. Answer: Cells in the striate cortex integrate information from a variety of visual cells in such a way that a cell may respond to visual stimuli that are more complicated than that of ganglion cells in the retina. An annular receptive field for each of a set of ganglion cells may report to a cell in the striate cortex in such a way that a bar of light that stimulates the center of each ganglion cell receptive field, causing the striate cell to fire. Stimuli that do not precisely stimulate the center fields of an array of ganglion cells would not stimulate the striate cortex cell. Different features (line, arc, circle) could be built up from different converging patterns to the striate cortex. 6) Define and explain what is meant by agnosia. Answer: The association cortex receives multiple streams of sensory information, which allows a human to use multiple modes to identify a stimulus. Your mother, for example, has a unique facial pattern, hair color, tone of voice, and odor. Damage to the association cortex can make it difficult for a person to recognize a stimulus, even though the person can still sense the stimulus. 7) Describe the role of the extrastriate cortex in the perception of movement. Answer: Neurons in area V5 respond to movement, whereas damage to this region impair the perception of movements. The medial superior temporal (MST) cortex is adjacent to area VT and plays a role in optic flow—the analysis of visual information as an observer moves toward an object. 8) Explain why Goodale argues that the actual function of the dorsal stream is "how" rather than "where." Answer: Goodale suggests that neurons in the posterior parietal cortex are involved in analyses that allow a person to locate an object in space and to judge the distance to the object as well as how to grasp or manipulate the object. 6.4 Essay 1) Explain the concept of a receptive field in the visual system and provide an example of this concept for a ganglion cell within the cat retina. Answer: Ganglion cells are the first cells in the visual system to show action potentials (APs), and it is possible to record the number of APs per unit time in a conscious animal while stimulating the retina with various lights. A receptive field is that portion of the visual field of the organism that responds to a light with a change in AP firing rate (increase/decrease). Ganglion cells in the cat show circular receptive fields. In some instances, the circular center responds with an increased firing rate when light is shown on the retina (ON response). Light shown on a ring around the center of such a cell would decrease the firing rate of the cell (OFF response). 2) Explain the organization of neurons into modules in the striate cortex. Specify which neurons respond to color, orientation, spatial frequency, movement, and retinal disparity. Answer: The striate cortex is organized into about 2500 modules, each containing about 150,000 neurons. Each module has two segments that surround a central region—termed a blob—that contains cells that stain positively for cytochrome oxidase. Cells within the blob receive information about color and low spatial frequencies. Cells outside the blob are sensitive to different orientations, movement, spatial frequency, and texture, but not color. Each neuron in the module receives information from the same region of the visual field. 3) Compare the anatomy and function of the dorsal and ventral streams. Answer: Visual information from primary visual is passed through a series of extrastriate cortex regions that modulate and integrate the information. From area V2, some signals ascend in a dorsal stream to visual association parietal cortex. The dorsal stream is involved in the analysis of spatial location. Other signals diverge from area V2 in a ventral stream that reaches the inferior temporal cortex. The ventral stream is involved in the perception of form. 4) Delineate the structure and functions of the magnocellular and parvocellular visual systems. Answer: The lateral geniculate nucleus of the thalamus (LGN) is organized into six layers. The inner two layers contain large cells (magnocellular), while the outer four layers are comprised of small cells. The magnocellular layers project to portions of the striate cortex that mediate visual processes other than color (e.g., form, movement, and depth). The parvocellular layers are involved in the perception of color and fine detail. Test Bank for Foundations of Behavioral Neuroscience Neil R. Carlson 9780205968091, 9780134639796, 9780205947997

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