A new study in the Proceedings of the National Academy of Sciences shows that adults who walked for 40 minutes three times a week for a year had brain growth in the hippocampus — an area of the brain associated with spatial memory. Study author Arthur Kramer and psychologist Margaret Gatz discuss their research.
http://www.npr.org/2011/02/04/133498136/growing-a-bigger-brain-is-a-walk-in-the-park?ft=1&f=5