Extrusion of one side of the parallel fibers during initiation of vertical migration of a granule cell.A, During the first 30 min, the granule cell (asterisks) located near the EGL–ML border (dotted line), had a single horizontal process extending toward the left side. Forty minutes later, the cell developed a small horizontal process (open arrow) at the rear part of its soma toward the right side. As a result of downward movement of the soma, the cell developed a T-shaped axon branch. Time interval (in minutes) is indicated on the bottom right of each photograph. Scale bar, 10 μm. The total distance traversed by the granule cell soma (B), the direction and distance traveled by the soma during each 5 min of the testing period (C), and the length/width ratio of the soma (D) were plotted as a function of elapsed time.