Here's a brain statistic for you

"Use it or lose it appears to be quite true when applied to the brain work of learning. Researchers find that children who are deprived of sensory stimulation develop brains that are 20-30 percent smaller than normal for their age. Although much remains to be learned about the neurological growth of the brain, some scholars believe that people quite literally build their own minds throughout life by actively constructing the mental structures that connect and organize isolated bits of information." ~~ Barkley, Major & Cross, Collaborative Learning Techniques: A Handbook for College Faculty