A thoughtful angle on dreaming.

A thoughtful angle on dreaming

The conventional view of dreaming depicts it primarily as an unconscious release of emotions and impulses held in check during the day. But a study of living brains at work suggests that dreaming also involves cerebral activity linked to conscious thinking and problem-solving.

Louis A. Gottschalk of the University of California, Irvine, and his colleagues studied the brain metabolism of 36 men while the men were awake and during rapid-eye movement (REM) and non-rapid-eye movement (NREM) sleep. Volunteers spent at least one night in a sleep laboratory. Radioactive glucose isotopes were delivered intravenously when brain waves and other physiological signs indicated the onset of REM sleep -- during which much dreaming occurs -- and NREM sleep. About 40 minutes after the isotope infusions, the researchers awakened the volunteers and asked them to report any dreams, as well as thoughts and feelings associated with the dreams. Immediately afterward, the team took positron emission tomography (PET) scans to determine the rate of glucose use in various brain regions during the interrupted sleep phase. They also administered PET scans after daytime periods of wakefulness.

Gottschalk and his co-workers scored each volunteer's verbal reports about his dreams or walking mental state for themes of anxiety and hostility. Overall, they found that wakefulness, REM sleep and NREM sleep were linked to different pattern of glucose use throughout the brain. However, REM dreams evoking the most anxiety and hostility were associated with rises in glucose metabolism in a section of the brain's frontal lobes that was comparably active while participants were awake and talking with an experimenter. This brain region is involved in conscious thought and reasoning, the researchers maintain.

Intense dreaming during RE, sleep apparently includes mental processes inherent in cognition and problem-solving, they conclude.