Hi, I thought you may like this Mentalrobics exercise from Braingle.com:
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Alzheimer's Prevention II

Mental exercise is one way to help prevent Alzheimer's [ For more on 'Alzheimer's' go here: http://www.braingle.com/mind/361.html ]. Another means of prevention is to remain physically fit throughout life. All of the organs in the body benefit from being physically fit, including the brain. One Harvard study of more than 18,000 participants found that people who got the most exercise showed less mental decline than those with sedentary lifestyles.

Physical exercise increases blood flow to the brain and keeps it working efficiently by stimulating the production of neurotrophins [ For more on 'neurotrophins' go here: http://www.braingle.com/mind/328.html ]. This is especially true for the hippocampus [ For more on 'hippocampus' go here: http://www.braingle.com/mind/330.html ] which is the first area of the brain affected by Alzheimer's disease. This increased blood flow and neuronal efficiency can reduce the natural shrinkage that occurs in the brain as it ages. An average person will lose between 15% and 25% of brain cells by the age of 90. Those people who get the most exercise will be at the bottom of that scale, while those people who never exercise will be at the top of that scale.
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For more mind exercises: http://www.braingle.com/mind/