Neurogenesis and plasticity in the CNS of adult birds.

Neurogenesis, typically a developmental phenomenon, continues into adult life in song birds. Cells born in the walls of the lateral ventricle migrate and differentiate throughout the adult telencephalon. I will argue here that birds take advantage of these new neurons as a form of plasticity. Most of the neurons connecting the different song control nuclei are born early in development. One important exception is the central efferent motor pathway for learned vocalization. This pathway is formed by projection neurons born during juvenile and adult life. Recruitment of new projection neurons at different times of the year and in different species correlates with vocal learning. Adult neurogenesis as a form of plasticity may serve learning and it may also teach us how to repair the damaged brain.