Two modes of radial migration in early development of the cerebral cortex

Layer formation in the developing cerebral cortex requires the movement of neurons from their site of origin to their final laminar position. We demon strate, using time-lapse imaging of acute cortical slices, that two distinc t forms of cell movement, locomotion and somal translocation, are responsib le for the radial migration of cortical neurons. These modes are distinguis hed by their dynamic properties and morphological features. Locomotion and translocation are not cell-type specific; although at early ages some cells may move by translocation only, locomoting cells also translocate once the ir leading process reaches the marginal zone. The existence of two modes of radial migration may account for the differential effects of certain genet ic mutations on cortical development.