Dual fate of subplate neurons in a rodent

While subplate neurons are lost in the development of the cerebral cortex of other mammalian species that have so far been investigated, in rodents the subplate (alternately termed layer VIb or VII) persists to adulthood, at least in part. We traced the developmental course of the subplate in the golden hamster, using two methods. We first used tritiated thymidine labeling to trace relative changes in the numbers of identified cohorts of cells in the subplate, layer VI, and the LGN. We also estimated the total number of cells in the subplate versus layer VI of the cortex from early in development to adulthood. These methods showed a high rate of cell loss in the subplate, between 50% and 80%, but with the clear retention of a substantial fraction of this early-generated population as a recognizable layer in adulthood. Species variations in the timing of cortical neurogenesis and the relative amount of cell loss in the subplate can be used to better describe the developmental function of this region.