See the link below to read a news story on a study with mice. Scientists found that an enriched environment promoted new neurons to grow and synapses to form. In fact they proposed that enriched environments involving both mental stimulation and physical activity can actually rewire the brain!
http://news.yahoo.com/s/hsn/20070501/hl_hsn/scientistsrestorelostmemoryinalzheimerslikemice
