... my Grandmother had the kind of Alzheimer's that made it so she couldn't communicate. She could get a few words out, then either stuttered or lost track of where she was.
She was out of the hospital room during my Grandfather's death, but we brought her in to see him after the nurses had left...
I stayed with my Grandmother at the Alzheimer's unit in the nursing home that night. For about two hours, she told me all sorts of stories from the past -- in with a lot of detail, and even people's names (the ability to use/remember people's names was one of her first things to go with Alzheimer's).
We went to sleep, and her lucidity wasn't around the next morning. I had a hard time convincing my family members that she was able to tell those stories. When they finally believed me, we guessed that it was the emotional trauma of seeing her husband's lifeless body that temporarily 'jarred' something in her brain.