"Neurogenesis" literally means "birth of neurons". Neurogenesis is most prevalent during pre-natal development and is the process by which neurons are created to populate the growing brain.

Adult Neurogenesis

Neurons are born in the adult. We know that adult neurogenesis takes place in the olfactory bulb and in the dentate gyrus of the hippocampus. Many of these newborn cells will die shortly after their birth.

The function of adult neurogenesis is not certain - although there is good evidence that hippocampal adult neurogenesis is important for learning and memory. Activities such as learning and voluntary exercise seem to promote their survival and successful integration into the existing hippocampus.

There is evidence that activity promotes neurogenesis in the hippocampus and that neurogensis helps the hippocampus to delete old memories and to form new memories (Deisseroth et al 2004 (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15157417&itool=iconabstr)).