Dad has vascular dementia ( and an Alzheimer's label though doesn't really fit the picture clinically).
Took some photos from the 80s and 90s in to the home and it was a dead loss! I was quite shocked. He just didn't really remember ( apart from ranting about his oldest friend who " just went off and married again after his missus died so bugger him" ) and says he didn't remember mum at all.
I suppose he can't compute things from different times. I'm me now, not a teenager/ early 20s as I was then. I hope the " can't remember your mum" is just an adaptation to life now, with him in a home and me visiting. I hope he hasn't really lost her completely from the corner of his memory.
Shan't do it again :(