You're much more likely to dream about fighting with your spouse, or other aggressive interactions, during REM sleep than non-REM sleep, according to a new study. This specialization of dream states gives further credence to the theory that dreams are more than just meaningless, chaotic images.
While we dream, the brain cycles through REM and non-REM sleep stages at 90-minute intervals. Dreams during both stages tend to mull over social interactions, leading some sleep researchers to speculate that dreams may help people better deal with these encounters. Researchers have also known that REM and non-REM sleep activate different areas of the brain. REM sleep, for example, stimulates the amygdala, which handles fear and aggression, while non-REM sleep kindles the forebrain, which plays a role in impulse control and more cognitive functions.
Cognitive neuroscientist Patrick McNamara of Boston University School of Medicine and colleagues wondered if these distinct activations resulted in different types of dreams. To investigate, the team collected dream and wake reports from 15 subjects over the course of 2 weeks. During the day, the researchers paged the subjects every 2 hours and instructed them to tape record their thoughts. At night, they did the same, but the subjects also wore a sleep monitoring system called "the nightcap" which differentiates between REM and non-REM sleep by counting head and eyelid movements. The researchers found that of the dreams that focused only on aggressive interactions, 21 occurred during REM sleep. Some aggression did show up in non-REM sleep, but in those dream arguments, the dreamer never initiated it.
"This refutes theories that say dreams are random mental activity," says McNamara, whose team publishes its results in this month's issue of Psychological Science. McNamara believes dreaming about social interactions may either help us better prepare for such interactions in the future or work through past interactions. If this is true, antidepressants may interfere with this management because many of these drugs suppress REM sleep, he says.
"I don't know of any other study that showed this kind of difference" between REM and non-REM sleep, says cognitive neuroscientist Richard Bootzin of the University of Arizona, Tucson. But he notes that further work will be needed to determine what role this difference plays in the daily life of the dreamer.