How to handle someone with Dementia

Alzheimer's (dementia) is a horrible disease, I watch both of my parents slowly slip from the real world. I was also told to visit with them & listen to their stories. This gave me a special insight to my father, who was living in the 40's in his mind during his service in WWII. I had read a few books written about the war & I talked with him. As he talked, he gave me his perspective of his service & army life during this time period. Some of times that I went to see him, I would see a momentary light in his eyes. This quickly faded as fast as it appeared & he was back in the 40's again.