Age differences in central nervous effects of visual deprivation in the dog

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Abstract
Visual deprivation in dogs during the first 5 weeks of life resulted in marked structural, biochemical, and electrophysiological changes which were not apparent in dogs similarly treated between 5 and 10 weeks of age or for 5 weeks as adults. These findings are discussed in relation to the period of integration, when structuro‐functional relationships of neural elements begin to reach adult‐like levels of organization. It was postulated that lack of stimulation of a sensory modality during this period would result in arrested development of the system so treated. This hypothesis was partially supported; although there was complete visual deprivation, some neuronal and myelin development occurred independent of visual stimulation. Visual evoked potentials were markedly abnormal in the youngest age group only. The findings suggest a “sensitive” period in the pathodevelopmental sense; development of a particular system is retarded if stimulation is inadequate. This period corresponds to the period of integration when structuro‐functional organization of component systems of the central nervous system occurs.