Many interneurons stay in the MZ for a prolonged period of time. The time course of the proportion of labeled cells remaining in the imaging field during time-lapse imaging in E12Ge:E15.5 GAD67-GFP (n = 1) and E12Ge:E15.5 wild-type (n = 7) cortices (A, B) or E15Ge:P1 GAD67-GFP cortices (C, D) (average ± SEM) is shown. A, C, The data from all labeled cells. Gray numbers with arrows indicate the number of brains examined at a certain period of time (e.g., in A, seven brains were examined between 15 and 29 h from the start of imaging). The total number of cells analyzed was 267 and 116 in E12Ge:E15.5 and E15Ge:P1 cortices, respectively. B, D, Dark gray squares, white circles, or light gray triangles indicate the data from cells showing stationary, wandering, or directed behavior, respectively. Because two cortices contained no stationary cells among the seven E15Ge:P1 cortices analyzed, the number of brains examined for the analysis of stationary cells at a certain period of time is indicated by the gray numbers with closed arrowheads in D. The total number of cells analyzed was 99 and 18 for stationary cells, 86 and 80 for wandering cells, and 88 and 18 for directed cells in E12Ge:E15.5 and E15Ge:P1 cortices, respectively.