Distribution of dendritic morphologies at different time points after cell division. A, with increasing time after labeling DCX-positive cells with BrdU, the cells progress through the 6 categories of dendritic morphology (cf. Fig. 2). At 4 weeks after BrdU, 45% of the labeled cells have reached the most mature stages E and F. Note that the absolute number of BrdU-positive cells has decreased by this time due to an activity-dependent selection process [2, 8] and that apparently, cells down-regulate DCX soon after reaching category F. Consequently, the relatively large proportion of DCX-positive cells in the potentially proliferative stages A – D (B) corresponds to only a low absolute number at late time points after BrdU.