Postnatal development of cat area 17: areal growth and tangential shape

Purpose. During the first few weeks of postnatal development the layers (if the kitten visual cortex differentiate and the anatomical features related to functional columns begin to emerge. Although, many aspects of the anatomical organization of visual cortex appear mature by 6 weeks ot age, little is known about the tangential growth of area 17 during postnatal development. We have measured the tangential extent of area 17 during postnatal development (1 week - adult) to determine the areal growth and 2D shape of the primary visual cortex. Methods- Tangential sections from unfolded and flattened visual cortex were examined from kittens (12 hemispheres) and adult cats (18 hemispheres). Sections were stained such that the border of area 17 was easily distinguished and the 2 dimensional area, anterior posterior length, and the shape were quantified. Results. In the adult, the average size of area 17 is 4.0 cm (range 2.9-3.8cm ). At 1 week of age the extent of primary visual cortex is approximately half the si/e of the adult. Growth is rapid over the first 6 weeks reaching 80% of adult size at the end ot this period, and attains adult si/e at approximately 12 weeks of age. During this developmental period the overall 2D shape of primary visual cortex remains the same. Conclusions. During the first six weeks of postnatal development in the kitten there is substantial areal growth of area 17 and when measured this crowth was found to be isotropic.