Inner Workings of Dreams Revealed

The brain operates in a unique way to create our highly visual, often bizarre dreams according to a new study, reported in the January 2, 1998, issue of Science. Using neuroimaging techniques, the report reveals that visual association areas and limbic regions of the brain isolate themselves from the primary visual cortex as well as the higher, more analytical areas of the brain during dreaming. This may explain why dreams are often highly visual, emotional and illogical.

"Rapid eye movement (REM) sleep, a period of intense visual dreaming, lends itself perfectly to study of how the brain creates visual images," said lead investigator Allen Braun, M.D., of the National Institute on Deafness and Other Communication Disorders (NIDCD), National Institutes of Health (NIH). He added that, "One pervading theory has that the entire visual brain is involved, to some extent, in visual imagination. Our results suggest that this may be true only during the conscious, waking state."

Dr. Braun's team, which included scientists from the NIH and Walter Reed Army Institute of Research in Washington, DC, used positron emission tomography (PET) to detect areas of the visual brain that were active during REM sleep in ten healthy young men. These areas were contrasted with wakefulness and slow wave sleep (SWS), a period of limited visual imagry, in the same ten men.

What the team found was increased blood flow, an indication of heightened brain activity, to the visual association areas of the brain during REM sleep. At the same time, decreased blood flow was observed to the brain's primary visual area, an area that receives visual images from the outside world. In addition, activity of the limbic system, the primitive, older, more emotional part of the brain was also heightened. This increased brain activity contrasted with decreased activity in the frontal cortex, that part of the brain that interprets and integrates information received from the visual and limbic systems, based on higher level processes such as memory, logic, and thought. "Lack of this higher level self-monitoring could explain why dreams can be so absurd," commented Dr. Braun.

"This study shows how imaging technology can reveal complex inner workings of the human brain to explain some of life's most vivid experiences," commented James F. Battey, M.D., Ph.D., Acting Director of the NIDCD.

As the nation's focal point for research in human communication, the NIDCD conducts and supports biomedical and behavioral research and research training on normal mechanisms as well as diseases and disorders of hearing, balance, smell, taste, voice, speech and language that affects 46 million Americans.

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