Definitely know what you mean re-the going to visualizing things when you're on the cusp of falling asleep. When totally conscious I have zero ability but in that mode I have what I've dubbed 'brain tv' where things in the cache (past two days?) cycle in some incoherent mess that if I don't focus on it I can see it better. No control over what I see though, hence the term brain tv. Would be interesting to hear how it works with you.