Fig. 1: Prefrontal birthdating experiment in nonhuman primate.

A Pen drawing of a macaque brain (side view) with the PFC indicated in pink. B Schematic overview of the time line for which [³H] thymidine ([³H]dT) injections were given at particular embryonic (E) time points indicated by green arrowheads. sac, sacrifice. C Relationship of time of origin and the final position of neurons destined for the PFC in macaque monkeys based on autoradiographic labeling of DNA replication by [³H] thymidine at various days of gestation (for details of the approach and methodology see Rakic [48]. Embryonic days are represented on the horizontal axis, vertical lines indicate the embryonic day on which an animal received a pulse of [³H]dT and the horizontal markers on the vertical lines represent the positions of heavily labeled neurons in the PFC. A schematic representation of the approximate position of layers I–VI and the white matter (WM) is indicated on the left (green rectangle). The data show that all neurons in PFC are generated between embryonic (E) day 40 and E90 within the 165-day-long gestational period in this primate species.