What Dreams May Come Come Not From Waking Memory
These results suggest that the images one sees during dreaming have nothing to do with conscious memory. Another finding supports this conclusion -- most of the Tetris players who saw falling Tetris blocks in their dreams did so not on the first day of play, but on the second day. Moreover, some of the expert Tetris players saw falling blocks in color with music playing -- just as they did when they played a different version of the game years before.
The study provides the best experimental support yet for the theory that dreams arise as the sleeping brain -- without help from the conscious mind -- strengthens the connections between different brain circuits that were created during learning. Because the players remembered only the falling blocks, and not the computer keyboard or other details unimportant for learning the game, the study also suggests that the brain strengthens only those circuits that appear to be most appropriate.
"In the process of reinforcing those circuits, their contents intrude on our awareness while we sleep -- in a nutshell, that's why we dream," Lee J. Kavanau, PhD, tells WebMD. "Our dreams are simply the contents of circuits that are activated. Most researchers believe that there is no method to it. Dreams don't necessarily serve any specific function -- but that doesn't mean that what's in them doesn't have any significance." Kavanau, emeritus professor at the University of California at Los Angeles' department of organismic biology, ecology, and evolution, did not participate in the Harvard study.
Michael Schredl, PhD, a sleep researcher at the Central Institute of Mental Health in Mannheim, Germany, was present when Stickgold earlier this year presented his findings at a conference of his peers. "Most people think that dreaming has to do with memory, and that the pictures of the dream are images that relate to waking-life experience," Schredl tells WebMD. "Therefore, it may be surprising if you ask a person about their waking-life experience and they don't remember it, but find that they can dream about it. On the other hand, when you work with people such as sexual abuse victims in early childhood, you can see that the images in dreams can reflect things that the person is not consciously aware of -- people dream of things they cannot remember in waking life. The dream memory system is not the same that the waking consciousness has access to."