If you guys are interested in this kind of stuff, I recommend checking out some books by Daniel C. Dennett. He is a leading cognitive scientist/philsopher(is it science or philosophy? Who knows!) and professor at Tufts University..The Mind's I is really entertaining and Consciousness Explained goes into exactly what you guys were talking about. The idea of being able to "visualize" something or "hear" something in your head fits into a theory of consciousness called the "Cartesian Theater" that Dennett believes is a poor way to describe consciousness. He is a smart guy and brings up a lot of very interesting things to think about. I highly recommend it.