Independent controls for neocortical neuron production and histogenetic cell death

We estimated the proportion of cells eliminated by histogenetic cell death during the first 2 postnatal weeks in areas 1, 3 and 40 of the mouse pariet al neocortex. For each layer and for the subcortical white matter in each n eocortical area, the number of dying cells per mm(2) was calculated and the proportionate cell death for each day of the 2-week interval was estimated , The data sh ow th at cell death proceeds essentially uniformly across the neocortical areas and layers and that it does not follow either the spatio temporal gradient of cell cycle progression in the pseudostratified ventric ular epithelium of the cerebral wall, the source of neocortical neurons, or the 'inside-out' neocortical neuronogenetic sequence. Therefore, we infer that the control mechanisms of neocortical histogenetic cell death are inde pendent of mechanisms controlling neuronogenesis or neuronal migration but may be associated with the ingrowth, expansion and a system-wide matching o f neuronal connectivity. Copyright (C) 2000 S. Karger AG, Basel.