The brain goes through significant developmental changes during the postnatal period that extend well into adulthood. A major component of this development is the addition of new neurons in the olfactory bulb and the hippocampus. While recent years have seen an explosion of interest in “adult” neurogenesis very little attention has been paid to the structural and functional contribution made by juvenile neurogenesis. The distinction between juvenile and adult neurogenesis has not been well defined, which has likely led to a number of discrepant findings and, more importantly, to an incomplete picture of the significance of postnatal neurogenesis as a whole. From both practical and theoretical perspectives, there are many outstanding questions regarding this distinction that remain to be answered. A practical definition of the transition between juvenile to adult neurogenesis needs to be agreed upon for both rats and mice, as well as humans. Theories regarding the functional contributions of juvenile versus adult neurogenesis also need to be formulated. For example, do their functional roles differ qualitatively or quantitatively? Furthermore, how do the current theories of adult neurogenesis apply to juvenile neurogenesis in a still developing brain? Perhaps most importantly, what role does juvenile neurogenesis play in the postnatal development of the human brain, particularly the hippocampus, which is known to grow in volume well into young adulthood? The aim of this special research topic is to bring together research and commentary that will aid in answering these outstanding questions regarding the structural and functional roles of juvenile versus adult neurogenesis.

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