7.7 Neurogenesis

Brains contain within them the seeds of their own salvation and the seeds of their own destruction. In its early stages, the brain produces vast numbers of neuroblasts as stem cells divide at a huge rate, churning out millions of potential neurons. By birth in humans, this process of neuronal proliferation has virtually stopped. There are, however, some localised areas of the brain, in the olfactory lobe and the hippocampus, for example, where neuronal stem cells survive well into adulthood. These stem cells can produce new neurons. What is not known is what controls the process. Under what conditions, in response to what signals will stem cells become active and start producing new neurons? Under what conditions, in response to what signals will stem cells become inactive and stop producing new neurons? All neurons though also contain the mechanism for apoptosis, for cell death. Under what conditions, in response to what signals will neurons switch on the cell death machinery that will lead to their own destruction? We don't know. But the answers to those questions would open up whole new avenues in the treatment of a variety of brain disorders.