What is it? Neurogenesis, or the birth of new neuronal cells, was thought to occur only in developing organisms. However, recent research has demonstrated that neurogenesis does indeed continue into and throughout adult life in both vertebrate and invertebrate organisms.
Examples of neurogenesis are found in the hippocampus of mammals, song control nuclei of birds and the olfactory pathway of rodents, insects and crustaceans.
On going neurogenesis is thought to be an important mechanism underlying neuronal plasticity, enabling organisms to adapt to environmental changes and influencing learning and memory throughout life.
Why is it important? A number of different factors that regulate neurogenesis have been identified.
Physicial activity and environmental conditions have been known to affect proliferation and survival of neurons in vertebrates as well as invertebrates. It has been found that crayfish in an "enriched" environment had increased neurogenesis and neuronal survival compared to siblings in an "impoverished" environment.
Hormones have also been found to influence the rate of neurogenesis in vertebrates (e.g. testosterone) and invertebrates (e.g. ecdysone). Serotonin is believed to play a key role in neurogenesis in a variety of organisms. In lobsters, depletion of serotonin dramatically reduced the proliferation and survival of olfactory projection neurons and local interneurons. Most recently, neurogenesis was found to follow a circadian rhythm in the juvenile lobster. Although neurons were born throughout the day, significantly more neurons were born at dusk, the most active time for lobsters. -http://www.wellesley.edu/Biology/Conc...