ANALYSIS OF THE POSTNATAL-GROWTH OF VISUAL-CORTEX

Development and growth of V1 begins during embryogenesis and continues postnatally. The growth of V1 has direct implications on the organiza tion of features such as the retinotopic map and the pattern of visual cortical columns. We have examined the postnatal growth and two-dimen sional shape of V1 in macaque monkeys, cats, and rats. The perimeter, area, and anterior-posterior length of V1 were measured from unfolded and flattened sections from neonatal and adult animals from each of th ese species. Although there were substantial differences in the overal l amount of postnatal growth, from 18% in macaque monkeys to more than 100% in cats, in all three species the shape of V1 did not change dur ing development. Thus, growth of the mammalian visual cortex is well d escribed as an isotropic expansion, so the layout of the global featur es, such as the arrangement of ocular dominance columns and the retino topic map, does not need to change during development. Furthermore, qu antification of the shape confirms the observations that there is a si milar; egg-like oval shape to the visual cortex of these mammalian spe cies.