> I 'm curious if anyone else has that happen. When I am still fully conscious but drifting off, with my eyes closed, I can make some image actually replace th

> I 'm curious if anyone else has that happen. When I am still fully conscious but drifting off, with my eyes closed, I can make some image actually replace the "black" we normally see when we close our eyes. The image just quickly fades in and replaces the "black". This started happening involuntarily a couple of years ago and, shortly after, I could also do it voluntarily. It is not completely effortless and it lasts for a few seconds though. I did a bit of searching and it seems that this is a normal experience while being in a so-called "hypnagogic state". So, what you are describing might also be a result of being in that state. When I am fully awake, a visualization is more like an imaginary overlay on top of whatever my retina is actually sending to my brain (thankfully :P).