Image streaming is somewhat like freewriting, but spoken aloud to someone else or to a recorder. Win considers it important that there be a listener. One of his claims is that the exercise increases the interconnections in the brain, to the point that one's IQ increases by 1 point about every 80 minutes of practice. However true that is, he has some interesting material, much of which can be found here:
Project Renaissance with Win Wenger, Ph.D.
It's been a while since I've done imagestreaming. Perhaps it'd be worth a 30 day trial, as the normal practice session is only five to fifteen minutes anyhow (the longer the better, as information is thought to improve towards the end), and there are plenty of potential benefits.