The contents of a person’s dream have been revealed by brain scan for the first time, scientists report in the Nov. 8 Current Biology. By monitoring the brain of a man who has unusual control over his dreaming, the accomplishment brings researchers closer to understanding how the brain spins its nightly yarns.
“It’s really exciting that people have done this,” says sleep researcher Edward Pace-Schott at Massachusetts General Hospital in Charlestown and the University of Massachusetts, Amherst. “And it also brings back lucid dreaming as a very powerful scientific tool.”
Lucid dreaming is the rare ability to direct behaviors while in a deep sleep. By all objective measures, the person is dead to the world: Most muscles are paralyzed and the eyes are doing the quick jitters that characterize REM, the main dreaming phase of sleep. But at the same time, the lucid dreamer knows that he is dreaming and can control the scenes, says study coauthor Michael Czisch of the Max Planck Institute of Psychiatry in Munich. “The world is open to do everything.”
Czisch and his team set out to catch a lucid dreamer’s brain activity with an fMRI machine. Instead of creating complex fantasias of flying over the Alps, scaling buildings or slaying dragons, six experienced lucid dreamers were asked to squeeze their left hands and then their right hands repeatedly in a dream. “It’s a rather easy thing to do,” Czisch says. “If it’s a random dream, things would be much more complicated.”
The dreamers and scientists worked out a “ready” signal. After the participants entered a dream while sleeping in the fMRI machine (a challenge because the machine is very noisy), they would look back and forth quickly with their eyes, which are still able to move during REM sleep. When the scientists saw these particular bursts of eye muscle activity, they knew the dreamer was about to attempt the squeezes.
Of the six dreamers, only one was able to pull the whole thing off. The fMRI revealed increased activity in a brain region important for movement called the sensorimotor cortex as the participant squeezed his hands in the dream. When the dreamer squeezed his right hand, the left side of his brain’s sensorimotor cortex had increased activity. When the dreamer squeezed his left hand, the right side of his sensorimotor cortex saw a boost.
Czisch and his team repeated the experiment while this participant was fully awake, and also while the man imagined squeezing his hands. Similar brain regions showed boosts in activity whether the hand-squeezing was performed, imagined or dreamed.
The work is preliminary, Czisch says. Because the results come from a single participant doing a simple, predetermined task, it’s not clear how other people would perform on self-generated dreams. “To get real insight into a complete dream plot is a bit science fiction,” he says. But improving methods might lead to a deeper understanding of how the brain weaves emotions, memories and thoughts into dreams, he says.