My grandfather supposedly has dimentia.. he never sleeps at night, he keeps on sobbing and calling his mother's name outloud, i don't think he's feeling any physical pain, anything i can do to help him mentally?

Sundowner: He may possess Alzheimer's and not unique to experience reversal of sleep/ waking cycle. Your doctor could provide medications to control some of this, but you could try: prevent daytime naps, schedule sleep and meals at same time daily, check with doctor for medications which have anticholinergic effects, keep a soft light on and a radio softly playing in his room. Good luck with this.