Scientists have long believed that mature brains can't grow or change other than losing cells with age. Now new research has reversed that dogma. Scientists found that London cab drivers' brains change as they memorize the city's layout. Growth occurs in the hippocampus of the cabbies, the area of the brain associated with memory and navigation.

		Alan asks van Praag about exercise and the brain

In "Grow Your Own Brain," Fred Gage of the Salk Institute in La Jolla, California, uses an bright green dye to confirm the existence of newborn cells in adult humans' brains. And Henriette van Praag has discovered that running twelve hours a night not only makes mice grow new brain cells, but makes the mice smarter too. No one knows for sure what that means for humans, but Alan Alda for one is anxious to find out if a little less running has the same effect.

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