DARK-REARING FAILS TO AFFECT THE BASAL DENDRITIC FIELDS OF LAYER-3 PYRAMIDAL CELLS IN THE KITTENS VISUAL-CORTEX

The development of the cat's visual cortex is incomplete at birth and is influenced by the cat's early visual experience. We have previously demonstrated that the basal dendritic fields of layer 3 pyramidal cel ls grow substantially during the first 5 weeks after birth and that st ripe-rearing affects their orientation. In this paper we determined th e effects on these dendritic fields of visual deprivation (dark-rearin g) during the first 3 months of life. The visual cortices of both norm ally reared and dark-reared cats were impregnated by the Golgi method, sectioned in the tangential plane and counterstained. The basal dendr itic fields of completely impregnated pyramidal cells from layer 3 wer e drawn with the aid of a camera lucida, and compared in terms of numb er and length of primary dendrites, branching, size, elongation, and d istribution of dendritic field orientations. Surprisingly, we observed no significant differences in any parameter measured. Thus, although stripe-rearing can specifically alter the orientation of the dendritic fields of the layer 3 pyramidal cells, and dark-rearing has been show n by others to alter the size of layer 4 stellate cells, dark-rearing failed to affect the dendritic fields of layer 3 pyramidal cells.