Chapter 23 112. The idea of a "critical period" in neural development is supported by experiments in which a. increases in weight or neuronal complexity of rat brains follow exposure of the animal to an "enriched" environment. b. eyes of ADULT salamanders are removed, and reinserted upside down, resulting in an upside-down visual field. c. eyes of kittens are sutured shut either at birth or after 2 months of life, with different effects on the physiology of the visual cortex. d. the cerci of a cricket are cut off after each molt, and the morphology of the giant interneurons in the adult is studied. 113. The time during development after which nervous systems have a sharply reduced sensitivity to disturbances in sensory input is called the a. critical period. b. neonatal period. c. deterministic period. d. specificity period. 114. In the development of the nervous system, a "critical period" is the period a. after which environmental factors can influence neural development. b. during which environmental factors can influence neural development. c. during the life of an animal when programmed cell death takes place. d. before which no neural synapses can be formed. 115. In the visual cortex of cats, ocular dominance "columns" or "slabs" are a. cells which receive input only from the dominant eye. b. cells which receive input only from the eye whose movement is controlled by the dominant hemisphere. c. cells which respond physiologically exclusively from one eye only. d. alternate layers of cells which receive input primarily from the right or the left eye. 116. The PHYSIOLOGICAL effect of unilateral eye suture (from birth to 6 mos) on the visual cortex of cats is a. a reduction in number of cells responding to light input from the closed eye. b. a reduction in number of cells responding to light input from the open eye. c. greater competition between right and left eyes for access to individual cortical cells. d. a reduction in binocularly driven cells, but not monocularly driven ones from either eye. 117. The properties of simple and complex cells in the visual system appear to develop and emerge primarily in accordance with the cells' a. pre-programmed connectivity. b. environmentally determined connectivity. c. both of the above. d. none of the above. 118. Suturing shut BOTH eyes of a kitten from birth to three months of age results in ____ß of the RETINAS of both eyes. a. strong disturbances in both the physiology and the anatomy b. strong disturbances in the physiology, but none in the anatomy c. strong disturbances in the anatomy, but none in the physiology d. no significant disturbances in either the physiology or the anatomy (No #119) 120. Suturing shut ONE eye of a kitten from three to six months of age results in a. strong disturbances in both the physiology and the anatomy of the visual cortex. b. strong disturbances in the physiology, but none in the anatomy of the visual cortex. c. strong disturbances in the anatomy but none in the physiology of the visual cortex. d. no significant disturbances in either the physiology or the anatomy of the visual cortex. 121. Suturing shut both eyes of a kitten from THREE to SIX months of age results in ____ß of the visual cortex. a. strong disturbances in both the physiology and the anatomy. b. strong disturbances in the physiology, but none in the anatomy. c. strong disturbances in the anatomy, but none in the physiology. d. no significant disturbances in either the physiology or the anatomy. 122. Placing a translucent covering (one that allows the passage of light, but not form) over the eye of a kitten for two weeks starting at age two weeks a. has no effect on vision in the adult cat in either eye. b. renders the retina of that eye unresponsive to light stimuli (i.e., blind). c. prevents the normal degeneration of the lateral geniculate nucleus on that side of the brain. d. none of the above. 123. One general conclusion that can be drawn from studies of the effects of the eye occlusion, suturing or other interference with visual system is that neurons (in the visual cortex at least) a. require binocular form input (stimulation) in order to develop or keep their proper synaptic connections. b. require only light in order to form their proper connections. c. require only form input (i.e., not just diffuse light, but lines or edges) in order to form their proper connections. d. do not show significant differences in the stimuli to which they respond if they are exposed exclusively to a horizontal or vertical visual environment. (No #12´-125) 126. The amount of surface area of the somatosensory cortex of a mammal that is devoted to a particular region of skin can expand after the loss or denervation of an adjacent part of the skin. This statement is a. true, but only for newborn animals within the first two weeks of life. b. false, because the organization of the somatosensory cortex is fixed at birth and cannot change even slightly after birth. c. true in at least some adult mammals like certain monkeys. d. false, because the amount of somatosensory cortex devoted to a particular region of skin only decreases as the animal ages. 127. Young rats raised in an "enriched" environment a. show an ability to learn mazes faster than controls, but show no differences in brain development. b. show an ability to learn mazes faster than controls, as well as an increase to cortex weight relative to the rest of the brain. c. show no ability to learn mazes faster than controls, but do show an increase in cortex weight relative to the rest of the brain. d. show neither an ability to learn mazes faster than controls, nor any differences in brain development. 128. Some morphological and physiological effects of an enriched physical environment manifest themselves on the brain a. only in young (immature) animals. b. only in males. c. only in females. d. in all animals, even mature ones. 129. The effect on the vertebrate brain of an enriched (physically and visually complex) environment is a. increased structural complexity and size of the cortex. b. none; i.e., there is no difference from the brain of a animal living in an enriched environment. c. a decrease in size of the entire cerebellum. d. a decrease in cortical size, weight and structural complexity. 130. The effect on the vertebrate brain of a simple environment (lacking in physical and visual diversity) is a. increased structural complexity and size of the cortex. b. none; i.e., there is no difference from the brain of an animal living in an enriched environment. c. a decrease in size of the entire cerebellum. d. a decrease in cortical size, weight and structural complexity.