Adult Neurogenesis in Injury-Induced Self-Repair: Use It or Lose It

One of the most hotly pursued topics in neuroscience and therapeutic medicine is the use of stem cells in the adult brain. Growing in parallel to this emerging field is the recognition that the adult brain is indeed capable of generating new cells. While neurogenesis was understood to be restricted to a few areas, recent studies suggest that damage to the adult brain can trigger neurogenesis even in regions outside of these specific areas. This finding raises the possibility that neurons born in response to perturbation in the brain may be involved in the recovery of function in the damaged adult brain. The key is understanding how to cultivate these newborn cells, because they do not remain viable if they are not accepted into the damaged network of interconnected neurons which support specific functions. From a birth site, undifferentiated precursor cells or neurons undergo migration and differentiation. Many factors influence the safe journey of migrating cells and their survival after maturation at their destination. This review will present evidence from ring dove studies that an activity-dependent mechanism underlies the survival of adult newborn neurons and establishment of their functionality. This evidence includes: [1] unique electrophysiological properties or specific connectivity associated with various type of neurons involved in ring dove coo behavior and reproductive function, [2] emergence of electrophysiological properties and specific projection neurons emanating from newborn neurons after hypothalamic lesion, and finally [3] collective behavioral analyses of social stimulations suggesting that sensorimotor events contribute to the integration of new neurons and reinstatement of function.