Thank you George for that.
One other thing that I would advise is to be patient and loving. I had a grandmother, who I can say was a second mother, the woman who truly raised me, who later on in life had dementia. During her dementia, I gave her a hard time as a teen. But one has to understand their situation, and I was a stupid stubborn selfish teen at the time. As I grew I realized the love she had for me, a love rooted in Orthodox Christian faith and sacrifice, and regardless of how I treated her, she never stopped loving me. I began to express my love back to her, although I felt it wasn't enough, since she was gone so quick.
And mind exercises are also important. Show them pictures reminiscing the times, ask them what they did during the day, get them to name all her children and grandchildren in the process, listen to their endless, and actually quite enjoyable stories, if you just listen. Things like that.
Love and appreciation again should be stressed. Laugh together and live together. If the mind is in a healthy, positive, happy state, the memory will be better, not to mention it's the loving and enjoyable thing to do.