File:Model of cortical neurogenesis.jpg

Radial Unit Lineage Model of Cortical Neurogenesis

a Based on the radial unit hypothesis12, 30,the model illustrates how changes in the mode and the rates of cell proliferation and/or programmed cell death within the neural stem cell pool (blue circles) in the ventricular zone (VZ) that divide symmetrically at early embryonic stages causes an exponential increase in the number of radial columns, which, in turn, results in surface expansion of the cerebral cortex without changes in its thickness. By contrast, similar changes in proliferation kinetics occurring in the founder cells (red circles), which divide asymmetrically, cause a linear increase in the number of neurons within radial columns without a change in the cortical surface area.

b The model of radial neuronal migration that underlies columnar organization based on Refs 12, 30 The cohorts of neurons generated in the VZ traverse the intermediate zone (IZ) and subplate zone (SP) containing 'waiting' afferents from several sources (cortico-cortical connections (CC), thalamic radiation (TR), nucleus basalis (NB), monoamine subcortical centers (MA)) and finally pass through the earlier generated deep layers before settling in at the interface between the cortical plate (CP) and marginal zone (MZ). The timing of neurogenesis (E40–E100) refers to the embryonic age in the macaque monkey12, 22, 32. The positional information of the neurons in the VZ and corresponding protomap within the SP and CP is preserved during cortical expansion by transient radial glial scaffolding. Further details can be viewed in the Rakic laboratory animated video of radial migration. RG, radial glia cell; MN, migrating neuron.

Part a is modified with permission from paper Ref. 147 © (2005) Macmillan Publishers Ltd. All rights reserved. Part b is reproduced, with permission, from paper Ref. 140 © (2007) Elsevier.

Original File name: Figure 2 Nrn2719-f2.jpg

Reference

<pubmed>19763105</pubmed>

Reprinted by permission from Macmillan Publishers Ltd.

http://www.nature.com/nrn/journal/v10/n10/fig_tab/nrn2719_F2.html