(A–D) Distribution plots of the mean percentage BrdU and ^{3}H-dT cells in bins of 100 μm from pia to (an including) WM. As indicated by color gradient, the transition from gray matter to WM is not an abrupt one. WM border usually initiates at about 1800 μm deep but this depends on the region, angle of cut, etc. (A and B) Injections at E70. (A) BrdU peaks for the PFC, LIM, MOT and SOM cortices coincide in depth between 200 and 300 μm from pia. The peak for VIS cortex is between 1000 and 1100 μm deep. Besides these peaks, for all BrdU cases there are other quasi salient peaks at different depths and in most cases >10% of the cells accumulate deeper to where no ^{3}H-dT cells accumulate. Between 2 and 3% of the cells are found at very deep locations including within the WM (>1900 μm from pia). Because of the spreading of the distributions, the largest accumulation of BrdU cells in a single bin is low, in the range from ~12–17%. (B) ^{3}H-dT peaks are discrete (i.e. separate from each other) and compact. In order of depth are LIM (at 300–400 μm), MOT (at 400–500 μm), SOM (at 500–600 μm), PFC (at 600–700 μm) and VIS (at 800–900 μm) cortices. There is no accumulation of cells at deeper locations and no cells found in the WM. Consequently, in each cortical area the largest accumulation of ^{3}H-dT cells in a single bin is high, in the range from ~15–37%. (C and D) Injections at E55. (C) BrdU and (D) ^{3}H-dT distributions are wider when compared to the corresponding ones for injections at E70 but, when compared to each other BrdU cells (C) are still more dispersed than the corresponding ^{3}H-dT cells (D). As with the E70 cases, the total percent accumulation per bin for BrdU is consequently lower that of ^{3}H-dT. The spreading of the BrdU cells is therefore a function of the marker and not of the time at which it was injected. To facilitate comparisons, all scales are the same and the position of BrdU or ^{3}H-dT distribution peaks are indicated by long and short dashed lines respectively.

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