Recent reports are conflicted about whether adult neurogenesis occurs in humans; discrepancies could arise from species differences in neurodevelopmental timing and differences in subject ages

Recalibrating the Relevance of Adult Neurogenesis. Jason S.Snyder. Trends in Neurosciences, https://doi.org/10.1016/j.tins.2018.12.001

Highlights

• Animal work has revealed that immature neurons born in the adult dentate gyrus have key cellular and behavioral functions.
• Recent reports are conflicted about whether adult neurogenesis occurs in humans.
• Discrepancies could arise from species differences in neurodevelopmental timing and differences in subject ages.
• Regardless of its extent, postnatally, an extended period of neurogenesis may produce a heterogeneous population of dentate gyrus neurons, due to prolonged cellular maturation and differences in the stage of the lifespan when neurons are born.
• These developments warrant a recalibration of when and how dentate gyrus neurogenesis contributes to cognition and mental health in humans.

Abstract: Conflicting reports about whether adult hippocampal neurogenesis occurs in humans raise questions about its significance for human health and the relevance of animal models. Drawing upon published data, I review species’ neurogenesis rates across the lifespan and propose that accelerated neurodevelopmental timing is consistent with lower rates of neurogenesis in adult primates and humans. Nonetheless, protracted neurogenesis may produce populations of neurons that retain plastic properties for long intervals, and have distinct functions depending on when in the lifespan they were born. With some conceptual recalibration we may therefore be able to reconcile seemingly disparate findings and continue to ask how adult neurogenesis, as studied in animals, is relevant for human health.