A temporal continuity to the vertical organization of the human neocortex

Radial translaminar arrays of pyramidal cells-minicolumns-are a pervasive structural motif of placental mammalian neocortex, which are anticipated in the earliest stages of cortical development by the formation of ontogenetic cell columns comprising radial glial cells and associated radially migrating neurons. In the present study we examine the temporal continuity in these structures throughout development and aging. Computerized image analysis of micrograph Nissl-stained postmortem tissue produced estimates of the median free path through neuropil in the radial direction (parallel to pyramidal cell arrays) and in the tangential direction (parallel to the cortical surface). These data were modeled as a biphasic power law with respect to in utero development and postnatal age, multiplied by a decay factor. No significant change in the ratio of radial to tangential neuropil space was demonstrated in either the prenatal or postnatal sample population. Neuropil development follows a prenatal phase of cubic volumetric growth with a postnatal phase of linear volumetric growth. The data suggest the continuity of columnar structures from early in gestation through postnatal maturation.