Final Report Summary - NEURAL RENEWAL (Neurogenesis in the adult human brain)
There has been a paradigm shift the last couple of decades, from believing that no new neurons are added to the brain after fetal development, to the realization that there is continuous addition of new neurons in certain parts of the adult brain throughout life. These studies have been conducted almost exclusively in experimental animals, and the extent and distribution of neurogenesis in the adult human brain has been poorly understood. We have explored neurogenesis in the adult human brain, mainly by measuring nuclear bomb test derived 14C in genomic DNA. This has demonstrated that there is more generation of new neurons in the adult human brain than most anticipated. We found that neurogenesis in the hippocampus, a part of the brain necessary for certain cognitive functions, is in many ways similar between humans and other mammals, although there are some distinct features in humans. The biggest difference, however, between humans and other mammals is that there is no detectable addition of new neurons in the human olfactory bulb, which is the most prominent site of neurogenesis in most other mammals, but there is instead extensive addition of new neurons in the striatum of the adult human brain, but not in other mammals.