Hi, I thought you may like this Mentalrobics exercise from Braingle.com:
-----------------
Brain Shrinking

The human brain reaches its full size by age 20 and then starts shrinking by about 1% per year. Male brains actually shrink slightly faster than female brains, but before you draw any conclusions it should be noted that there is no evidence that brain size determines ability. Rather, it is how your brain is constructed that matters.

The decrease in brain mass is not due to the death of neurons [ For more on 'neurons' go here: http://www.braingle.com/mind/317.html ]. In fact, recent research is showing that you can actually make new neurons as you age. The shrinkage is mostly due to changes within the neurons. In particular, the number of branching dendrites and connecting synapses decreases with age. Additionally, age causes the deterioration of the protective covering that surrounds the neurons. This may contribute to decreased mental performance.

Smoking, drinking and high cholesterol are all thought to hasten the shrinkage of the brain, so there's yet another reason to give up your vices.
-----------------
For more mind exercises: http://www.braingle.com/mind/