Ms. Latshaw used to be full of life. She loved to cook, played tennis and bridge, raised two children and took charge of redecorating the grand old family home. Then her memory began to slip: guests would arrive for dinner, and she would have no memory of inviting them. She forgot to look before pulling into traffic, and nearly caused an accident. She would wander out of the house, and local store clerks would take her home. She never turned hostile or angry, as many demented patients do, but she had vivid hallucinations of strings being caught in her teeth, and little men getting into her bed and jabbing her with broom straws. On especially bad nights, her husband would get up with her at 2 or 3 a.m. and make the two of them hot chocolate.

Aricept, an Alzheimer’s drug, made the hallucinations worse, while another drug, an antipsychotic used for schizophrenia, seemed to quell them. But the second drug had side effects: after taking it for several years, Ms. Latshaw began to grind her teeth, and could not stop moving her arms and legs.

Their father also suffered from dementia, Ms. Hess said, admitting that she wonders about herself.

“Naturally I’m a little bit concerned, but I think worry is such a waste of time, so I don’t dwell on it; I just don’t,” she said. “My friends always said, ‘You always had a bad memory.’ I see Barbara and David’s children having that same kind of memory.”

Ms. Hess has volunteered for studies at the University of Pittsburgh Medical Center, where she became the first person in the United States to have a PIB study of her brain.

“I’m very anxious to get to the bottom of this whole Alzheimer’s thing,” she said.

Nothing Left to Give

In an interview in the summer of 2006, Ms. Kerley described her mother this way: “She’s completely withdrawn in herself. She hasn’t recognized us for a few years. Basically she hums one line of one song over and over again. She seems to be stuck somewhere in her life between age 4 and 5.”

Ms. Kerley said she and her son Michael, then 21, visited every week or two.

“She loves getting her back rubbed, being smiled at, being hugged,” Ms. Kerley said. “She doesn’t know who we are. We’re going for us, not for her, because she doesn’t remember us the minute we walk out the door.”