Neurogenesis, the formation of new functioning neurons in the adult mammalian hippocampus has been definitively proven, according to researchers at the Salk Institute for Biological Sciences.
The finding suggests a potential for neurogenesis-based therapies for some types of brain damage or disease. The researchers also noted that the rate of neurogenesis increases when the adult mouse is physically active.

Nature 415, 1030 – 1034 (28 Feb 2002)