Isochronic transplantation of early-born (E12.5) MGE cells gave rise to mostly lower layer interneurons in the neocortex. A, βgal+ cells are distributed in the lower cortical layers (boxed) and in the striatum (St). Dotted line demarcates white matter (WM). B, Higher magnification of boxed area in A shows scattered cells in mostly layer 5 and occasional cells in layers 3 and 4. C, Schematic diagram showing the locations of βgal+ in lower cortical layers, after combining data from the reference section of six transplanted brains (adapted from Swanson, 1998). Note that only data from neocortical cells are depicted here. D, The layer positions of βgal+ cells (n = 549) from six different animals were assigned to 10 bins spanning from the white matter to the pia. The tabulated histograms (percentage ± SEM) indicate lower layer positions of early-born interneurons after isochronic transplantation. Scale bar (in B): A, 375 μm; B, 150 μm.