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Dark rearing in the cat: Effects on visuomotor behavior and cell growth in the dorsal lateral geniculate nucleus
Author(s) -
Kalil Ronald
Publication year - 1978
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901780304
Subject(s) - darkness , cats , geniculate , biology , lateral geniculate nucleus , sensory deprivation , anatomy , nucleus , neuroscience , visual cortex , medicine , sensory system , botany
The morphological and behavioral effects of complete binocular deprivation were studied by rearing cats from birth in total darkness. Nineteen animals were sacrificed immediately upon removal from the dark at intervals that ranged from 3 to 16 weeks. Measurements of cell sizes in the dorsal lateral geniculate nucleus revealed that dark rearing affects cell growth in two stages. During the first three months of dark rearing the growth rate of geniculate cells is reduced, and a maximum size difference between cells from light reared control animals and dark reared cats is seen at 12 weeks. However, during the fourth month of deprivation, geniculate cells recover from the effects of dark rearing, and grow to essentially normal size by 16 weeks. In a separate set of experiments, cats were removed from the dark at 8, 12 and 16 weeks, and given normal visual experience for as long as one and one‐half years. Lateral geniculate neurons in these animals were also normal in size. These results indicate that the effects of dark rearing on cell growth in the lateral geniculate nucleus are significant, but transitory, since they can be reversed either by long term deprivation, alone, or by exposure to normal levels of illumination. Behavioral experiments were performed to study the influence of dark rearing upon visually guided avoidance, jumping, placing, and following. After 8, 12 and 16 weeks of dark rearing, cats appear blind when first examined, and fail each of the behavioral tests. Within four weeks, however, visuomotor behavior recovers almost completely. Visual field perimetry testing was also carried out, and the results indicate that orientation is not reliably affected by periods of dark rearing less than 12 weeks in duration. However, 16 week dark reared animals show visual field defects, which persist for several months, and suggest that only the nasal hemiretina is used for orientation. Since the dark reared cats which showed deficits in orientation also demonstrated a pronounced convergent strabismus, it is proposed that misalignment of the visual axes may be directly responsible for the behavioral impairment.