I observe similar "euphoric" behvior in my father. By euphoric, I mean a lot of things - the spontaneous "C'mon, let's go to Florida, I'll call the travel agent" (Dad can hardly go out of the house let alone Florida); the periods of phoning all his old friends; the general feeling that he can do anything. I suspect it's the drugs - sometimes I think the drugs have almost everything to do with his cognitive loss, his dementia, and his euphoria.