Fronto-temporal dementia means that you don't lose your memories - you just lose your character, your speech, your finer instincts - as well as (like other dementias), your ability to walk, to swallow. Mum always knew who we (and all her friends) were, right to the end - but as I said to my dad, she stopped wanting to access any other memories.
But every dementia is different: I hate it when people say, "Music is always a way to reach them." No. It's. Not.
My mum had been a singer, sang in a choir, loved all music (classical and classic pop) - but towards the end, stopped even wanting to listen to it.
It actually scares me, the thought that Trump might have a form of dementia
My mum began over-reacting to the slightest thing - for example when ds (then 7) started reading Captain Underpants with all its childish grammar. Mum was appalled
- yet the English teacher part of her would (normally) have been pleased that ds was finally reading 
Heaven knows what his lack of inhibitions might lead to
I just hope he has a good team around him who are keeping an eye on him and giving him the wrong codes