It is a common psychology for the elderly to pick up junk: pick up the lost years! A kind of nostalgia. It's not the brain.
What shall we do? Suggestions:
1, pay grandma more to talk about the past and recall the "lost years" together. ...
2, find something for grandma to do. For example, keep a dog (or cat) and feed it.
Take a bath (if there are fleas, you can take a bath with sulfur soap) and take it out to play. ...
I often take my grandma to parks and museums, and I can also give her a class to learn calligraphy and painting. A colorful life can reduce the loneliness of the elderly.
The above opinions, I hope to have reference for you.