@Laotionne - Who wouldn't want to believe that doing puzzles and doing brain exercises for memory will help all of us avoid senility in our old age? I certainly hope this is true, but I tend to lean the other way.
My mother didn't read much, she didn't do brain exercise and she eventually suffered from dementia. Actually, she developed this condition early. So you might say that this is another example of how lack of brain exercise can lead to dementia. However, in the assisted living facility where she lived the last years of her life, there were plenty of people in the same condition as she was in.
Many of the people in the facility had done brain exercises of some sort and they still developed dementia and memory loss. I think if you live long enough then there is a good chance that you will start to slow down mentally regardless of what brain exercise games you do.