MONTREAL – Revealing his thoughts to his writers’ circle last August, Harvey Berger wrote: “It isn’t every year a man celebrates his 80th birthday. How does it feel to be 80? I cannot really complain. I think my marbles are still all in a row. None litters the floor. Oh, there is some litter, but no marbles.”Berger, whose Alzheimer’s disease, the most common form of dementia, was diagnosed when he was 76, is no slouch. He rattles off where he gets to: art class at the Alzheimer Society of Montreal offices, a Tuesday writers’ circle and a Friday support group at the Cummings Jewish Centre for Seniors, cinemas, museums and the three libraries he frequents. But more important than where he gets to is why he’s there.