Where dreams are made
John Wiley & Sons, Inc. and
World Science Staff
http://www.world-science.net/newspg2/040910_dreamfrm.htm

Scientists are learning new facts about dreaming, including which part of the brain produces dreams, by studying a woman who lost her ability to dream.
The 73-year-old woman had a stroke in the post cerebral artery, a blood vessel that supplies blood to the back of the brain. The stroke damaged an extensive area of brain tissue and eliminated her dreams for about a year, the scientists reported.
Scientists already had some idea which brain area generates dreams. The study of this rare case helped them map that area more precisely, they said. It also gave some insight into the relationship between dreaming and so-called REM sleep, the part of the sleep cycle in which dreams normally occur.
"How dreams are generated, and what purpose they might serve, are completely open questions," said Claudio L. Bassetti of the University Hospital of Zurich in Switzerland, who conducted the study with the woman.
When the stroke cut off blood flow to a small area deep in the back of the her brain, she lost several brain functions, mostly vision-related. Fortunately, the visual problems went away within a few days of the stroke. But a new symptom emerged: her dreams stopped.

Such loss of dreaming, along with visual disturbances, following brain damage is called Charcot-Wilbrand syndrome, after the neurologists who first described it in the 1880s. The syndrome is quite rare, especially cases that lack symptoms other than dream loss.
Bassetti and colleague Matthias Bischof realized that this woman's misfortune might help explain which brain area produces dreams.

For six weeks following the stroke, they studied her brain waves as she slept. They found her sleep cycle was normal. During a part of the sleep cycle the REM (rapid eye movement) sleep, there were no abnormal brain wave patterns, the researchers said. This seems to confirm that different brain systems drive dreaming and REM sleep, even though these two things normally occur together, they added.

Before the stroke, the patient recalled, she had dreamt three to four times a week. Afterward, reported no dreams. Eventually, a year after the stroke, some dreams returned, but no more than once weekly, she reported. The dreams were also less vivid and intense than before.

Using brain scans, Bischof and Bassetti found the stroke had damaged areas deep in the back half of the brain. Research has shown that some of this region is involved in visual processing of faces and landmarks, as well as the processing of emotions and visual memories. This is a logical set of functions for a brain area that would generate or control dreams, the two scientists said.

"Further conclusions about this brain area and its role in dreams will require more studies analyzing dream changes in patients with brain damage," said Bassetti. The two published a study on the findings in September 10 online issue of the research journal Annals of Neurology.