Scientists Learn To Program Human Dreams

Boston, MA--October 12, 2000--A team of Harvard Medical School scientists has achieved what researchers since Freud's day have sought: a way to control--at least in part--the content of a person's dreams. They are using their dream-provoking method to explore age-old questions, such as: Where do dreams come from? What do they mean? What is their role in memory, learning, and creativity? What is their link to the unconscious?

For years, scientists have been stymied in their quest to understand these associations because dreams are unique events that cannot be replicated. Until now. Robert Stickgold, HMS assistant professor of psychiatry, and his colleagues report in the Oct. 13 Science that they were able to get 17 different people to see the same dream images as they drifted off to sleep.

Stickgold and his colleages elicited the carbon-copy images using the computer game Tetris, training 27 subjects--12 novices, 10 experts and 5 amnesiacs--to play the game over the course of three days--a two-hour morning and one-hour evening session the first day and an hour-long morning and evening session each of the following two days. They then monitored the subjects' dreams as they were drifting to sleep on the first two evenings.

Seventeen of the subjects, over 60 percent of the total, reported dreaming at least once in the hour after they fell asleep, and all reported the exact same dream images--falling Tetris pieces. And intriguingly, the majority of dream reports occurred on the second rather than the first night of training.

This lag between first training and most intensive dreaming is interesting for the light it may shed on the link between learning and dreams. It appears that the need to learn may actually prod the brain to dream. "It's as if the brain needs more time or more play before it decides, 'Okay, this is something that I really need to deal with at sleep onset," Stickgold said.

Perhaps the most surprising findings of all came from the amnesiacs in the study. Co-author David Roddenberry found that when the five amnesiacs--who had no short-term memory due to hippocampal damage--were exposed to the computer game protocol, three of them experienced the same hypnagogic dreams as the normal subjects.

"I was just stunned when David called me and said they're getting them," Stickgold said. Though amnesiacs were known to dream, their dreams were thought to have little to do with the day's events, since those events are not remembered. Stickgold had assumed that this would be especially true of the early, or "hypnagogic," stages of dreaming explored in their studies. Compared to later stages of dreaming, such as those occurring during deep sleep or REM sleep, hypnagogic dreams were thought to be more tightly linked to conscious, or episodic, memory. "We thought if there's one part of sleep that depends on episodic memories, which amnesiacs lack, its sleep onset," he said.

The fact that some of the amnesiacs saw the falling Tetris pieces points to the powerful role played by the unconscious in dreams. In fact, Stickgold believes that the amnesiac's unconscious Tetris memories may have affected not only their dreams but their waking behavior. Unlike the normal subjects in their study--who improved in their computer games over the course of the three days--the amnesics showed marginal improvement. Most had to be taught the game all over again each day. But Roddenberry, an undergraduate at Harvard University, observed that at the start of a session, one of the amnesiacs placed her fingers on the exact three keys used in playing Tetris.

"She did not quite know what she was doing and yet she did know what she was doing," said Stickgold. "In a way, this is Freud's unconscious--things activated in our brain, that are in fact memories that guide our behavior but are not conscious," he said.

The notion that dreaming is prompted by a need to learn was supported by other findings as well. The researchers found that novices who reported seeing falling Tetris pieces did not perform as well in their initial two hour Tetris training session as those who did not see the images. "It's as if the more work you have to do, the more likely you are to get the imagery," said Stickgold.

Those who needed to do the least work were the experts in the study, each of whom had previously logged at least 50 and as much as 500 hours of Tetris playing, mostly on Nintendo sets. Half of them reported dreams of Tetris pieces falling before their eyes, but the last two experts reported an intriguing twist. Rather than seeing the Tetris pieces in black and white, as they were shown in the experimental protocol, they saw them as they appeared in their earlier Nintendo Tetris-playing days--in color and accompanied by music.

This substitution of old images for new ones strikes at the most distinctive quality of dreams--their often astounding creativity. In dreaming, the brain does not merely replay memories but transforms them by associating them with old images and memories. "It's actually hunting around and finding other relevant information to connect to, which is the integrative process--which over time, I would argue, is a critical function of sleep," said Stickgold.

"What we're really looking at here is the age-old mind-body problem: the mind-brain connection," said Stickgold. "We think of our mind as being ours. But there are real ways in which the brain has a set of rules of its own. We're getting an idea of what the brain uses as its rules for picking out cortical memory traces to reactivate and bring into our conscious mind, and, we're trying to see across wake-sleep cycles how that process happens."

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Support for this research was provided by the National Institutes of Health and The Network on Mind-Body Interactions, a multidisciplinary research network sponsored by the John D. and Catherine T. MacArthur Foundation. Begun a decade ago, the Mind-Body Network (www.mindbody.org) has been committed to discovering the biological mechanisms by which the social world and mental processes affect physical health.