Model of the quantitative and qualitative differences in the effects of attractants, repellents, inhibitors, and inducers on migration from SVZ explants. The top colored circles represent aggregates of cells secreting putative regulators of migration. The small blue circlesrepresent SVZ explants, and the larger light-blue circles represent the migrating cells. The size of the circle signifies the number of cells; their location relative to theinner circle shows the preferred direction of migration. The orange line shows the separation between the distal and proximal hemispheres; the dashed lines facilitate the comparison between control and experimental points. Thetriangle on the right depicts an expected concentration gradient of the molecules.