Development of cytochrome oxidase blobs in visual cortex of normal and visually deprived cats

Cytochrome oxidase (CO) blobs are central to our understanding of the colum nar organization and parallel pathways in primate and cat visual cortex. In primates, development of blobs and their relationship with other columnar features of the visual cortex begins pre-natally, before visual experience. In kittens, the supragranular layers differentiate post-natally, after eye opening, raising the possibility that visual experience may influence the development of blobs in cat V1. We have examined the development of blobs i n unfolded and flattened sections through the visual cortex of normally rea red, dark reared, monocularly deprived and binocularly deprived kittens. Bl obs were found in superficial layers of V1 of normally reared kittens as ea rly as 2 weeks of age, although at this age the overall GO staining in V1 w as lighter than in V2. By 6 weeks of age the blobs were adult-like. A patch y pattern of CO staining was also found in V2 of young kittens but not in a dults. Visual experience was not necessary for expression of the blobs and monocularly deprived kittens had well developed blobs, indicating that stro ng Y cell drive is not necessary for the development of blobs in cat V1. CO blobs appear in kitten V1 very early in post-natal development and their e xpression is independent of visual experience, suggesting that they may be an intrinsic feature of V1 organization.