Actually I called this technique "learning by osmosis" when I was in high school. I had the high hopes that sleeping with my head resting on the text book would absorb some of the words as I slept in class....

Seriously though, there's got to be some reasoning behind those language tapes... where you listen to basic words while you sleep. Sometimes sleep is meant to help solve problems, isn't it?

Cardinal recommends learning immediately before sleep. "Revise your material several times; try to commit it to memory. This allows the brain the time it needs to store and compile the information so it will be there when it's required. Then, off to bed, let the brain do the rest. You'll be surprised at how much you retain."
This part, yeah That's what I was getting at. I doubt you could be fluent in a new language in a week though... but who knows?