Extended Data Figure 5: Young neurons are present in the infant but not the adult human DG.

a, DAB staining in the hippocampus at birth reveals many young neurons in the GCL. b, DCX⁺PSA-NCAM⁺ cells are distributed in clusters across the GCL at 1 year of age. Most PSA-NCAM⁺ cells are DCX⁺, but some are DCX⁻PSA-NCAM⁺ (arrows). c, In the samples from a 13-year-old individual, DCX⁺ cells have a more mature neuronal morphology. The cell shown is NeuN⁺ and has dendrites in the molecular layer (arrowheads) and an axon projecting into the hilus (arrow). d, At 35 years of age, the DG does not contain DCX⁺PSA-NCAM⁺ cells, but does contain many DCX⁻PSA-NCAM⁺ cells that do not have the morphology of young neurons. e, PSA-NCAM⁺ staining in the human DG from 3 weeks to 77 years; in adults, these cells have a more mature neuronal morphology and are localized in the hilus. f, PSA-NCAM⁺ cells in the DG are NeuN⁺ in samples of 19- and 77-year-old individuals. g, At 3 weeks of age, the GCL and hilus were filled with clusters of DCX⁺NeuroD⁺ cells, and many of the DCX⁻ GCL neurons were NeuroD⁺. At 35 years, no DCX⁺NeuroD⁺ cells were observed; antibody labelling for NeuroD was non-specific. Scale bars, 200 μm (a, d–g), 20 μm (b, c, and d, f, g (inset)).