I dunno it seems somewhat true. I know there MUST be a correlation between REM and cannabis though. I NEVER remember my dreams if i've been smoking a lot. When I take breaks I tend to have a lot of vivid dreams. Now what cannabis does to memory i'm not sure. I think it allows people to notice details and see the big picture, allowing them to relax from the little troubles and stuff in life. It deffinatley helps me concentrate by filtering out a lot of little annoying thoughts I tend to have.