The brains of all higher order animals are filled with a diverse array of neuron types, with specific shapes and functions. Yet, when these brains form during embryonic development, there is initially only a small pool of cell types to work with. So how do neurons diversify over the embryo’s development? Researchers know that neural stem cells called neuroblasts divide multiple times to sequentially produce neurons of specialized function, but the mechanisms of this process, and how the timing varies for different genes and neuron types, is still not fully understood.

Many new parents are familiar with terms like “baby brain” or “mommy brain” that hint at an unavoidable decline in cognitive function associated with the hormonal changes of pregnancy, childbirth, and maternal caregiving. A new study of parental care in stickleback fish is a reminder that such parenting-induced changes in the brain and associated shifts in cognition and behavior are not just for females—and they’re not just for mammals either.