Researchers have used advanced techniques to show that, in a key memory region of the brain called the hippocampus, immature, plastic neurons are present in significant numbers throughout the human lifespan. The findings may resolve a long-running controversy over the existence of 'adult neurogenesis'-- the production of new immature neurons in the mature human brain. The discovery also paves the way for the deeper study of adult neurogenesis and its roles in memory, mood, behavior, and brain disorders.