I don't think that it is a "lie" in the usual sense of the word.
With my bi-polar ex it wasn't a lie (exactly)...he really believed the crap he would say!
Nothing could convince him he was wrong.
Combined with a stoke (loss of memory).. he was nasty and rude too.
He knew he had a faulty memory (I think) but was totally sure of totally untrue things.
I have heard that in a manic phase, even without a stoke, this is common.