Scientists still disagree over why brain needs sleep

WASHINGTON -- When you're asleep, your mind uses dream time to process information for use when you're awake. Or not.

New research papers from sleep scientists, featured in the November issue of Science magazine, reach opposite conclusions.

Robert Stickgold, a professor at the Department of Psychiatry at Harvard Medical School, produced research he believes provides compelling evidence that the mind works hard at night.

"The brain is taking information and helping us put it into a form that we can understand," Stickgold said. "Understanding the complexity of the world is one of our brain's most difficult tasks. It needs more than our hours of awake time to get the job done."

Across the divide is Jerome Siegel, a researcher at the Center for Sleep Research of the Department of Veterans Affairs. Siegel's analysis, which looks into dozens of studies done on dreams and learning, found no evidence that the sleeping mind does anything important.

"Since the beginning, there have been all sorts of theories about what happens when we sleep and dream," Siegel said. "Hundreds of years ago, people said we dreamt to get in contact with our ancestors. The latest theory gaining some acceptance is that our brain is solving problems and helping us learn. There is no evidence of that."

Test subjects kept awake

Both scientists pronounce their evidence solid.

In Stickgold's experiment, people were given complex problems to solve and tested on their solutions over the next several days. Some of the people were allowed to reach REM sleep (the deepest form of sleep), while others were kept awake.

Stickgold says the people allowed a full night's REM sleep improved more than the sleepless subjects. He believes the research suggests that part of the brain uses weak traces of memory to produce dreams while another part assimilates new information, putting it in order and helping the brain understand it.

In its simplest form, Stickgold's research suggests that the common anecdote of people going to sleep with a problem on their mind and waking up with a solution has scientific backing.

Siegel's sees other explanations for why the people allowed to sleep in Stickgold's experiment appeared to better solve their problems.

"There is a great deal of stress involved in depriving someone of REM sleep," he said. "That stress can make someone perform worse."

Outside observers seem to fall on both sides.

"It seems clear that the brain does help us learn and process information while we sleep," said Russ Carter, a psychiatrist in Austin, Texas.

Linda Sveena, a sleep researcher at Ohio University, takes the other side.

"We don't know that their brain is working to process information while they sleep," Sveena said. "The evidence of this is scant."