Fig. 6. Proposed mechanism for the migration of cortical interneurons from the MGE. The TAG-1 immunopositive fibers are depicted in green, migrating interneurons in red, radial glial fibers in yellow and Slit1 mRNA in blue. MGE cells migrate away from the GE probably owing to a chemorepulsive effect of Slit1. They then use the TAG-1 immunopositive axons arranged tangentially in the MZ and IZ to migrate into the neocortex. They reach their positions in the CP by using the radially arranged bundles of efferent axons or radial glial fibers.