ABSTRACT
Multiple regenerative mechanisms are initiated after brain damage occurs. Some of these, such as metabolic compensation, reactive synaptogenesis and collateral sprouting, involve neurons that survived the damage. However, in cases of severe damage or degeneration, these mechanisms are not sufficient, and the addition of new neurons may be a prerequisite for functional recovery. It is now generally accepted that new neurons are added to the adult mammalian brain. This raises the possibility that naturally occurring neurogenesis may be useful for repairing the damaged adult brain. Indeed, several studies have shown that damage to the adult brain can stimulate neurogenesis. Yet the production of new neurons is only one of multiple steps necessary to restore damaged neural circuits to their original state or the functional equivalent. Studies carried out on intact animals have identified conditions that affect the production and survival of new neurons in adult brains. This chapter considers the evidence for compensatory neurogenesis in the adult mammalian brain, with a view toward applying information from the undamaged brain to studies of regeneration.
