Understanding Weird Dreams

Oct. 14, 2001 -- A study involving peoplewith amnesia, a popular computer game and sleep experts mayhelp explain why dreams are so weird and so important, expertssaid Thursday.

They said people with amnesia who played the popularcomputer game Tetris dreamed about the images it invoked, butcould not remember actually playing the game. And, unlikepeople with normal memories, they never really got any betterat the game.

Subconscious Filing

This shows that when the brain is filing away the memoriesit needs to keep, it has to go through a series of steps, anddreaming is a manifestation of one crucial step, Dr. RobertStickgold, a psychiatrist at Harvard Medical School in Boston,who led the study, said.

Dreams are just the body’s way of clearing out the mental“in-box,” Stickgold said.

“The trick is to move it to the file cabinet and to file itin the right place,” Stickgold said in a telephone interview.

“A lot of REM [rapid eye-movement] dreams, those reallyquirky, strange, bizarre dreams that we have late at night, isthe brain looking for ways to cross-index. It is looking forcross references — does this fit with this? Sometimes it doesand sometimes it doesn’t,” he said.

When it doesn’t fit, the dream seems weird, he said. Whenthe cross-reference is a good one, the brain can reinforce thememory.

One way to test this is to look at people who are missingone of those vital memory steps — people with amnesia.

Tetris on the Brain

Stickgold had noticed that when he skied, he had vividdreams about it.

“When you go downhill skiing, when you go to sleep, you canfeel the turns,” he said. This would make a good test, he said,but added he knew he would never get the OK to takefirst-timers downhill skiing for a scientific experiment.

And then someone mentioned Tetris, a computer game thatuses vivid images of falling and rotating shapes that have tobe manipulated by the player.

It, too, evokes dreams, Stickgold said. “I play Tetris,that is all I see going to sleep,” he said.

Writing in today’s issue of the journal Science, Stickgoldand colleagues said nearly two-thirds of the 27 volunteers theyasked to play Tetris had dreams about it.

Their group included five people with amnesia, caused bydisease, stroke and other accidents. Experts at the game andfirst-time players were also tested.

People in both groups reported that, as they fell asleep,they dreamed about images of blocks falling and rotating, asthey do on the computer screen when the game is in progress.They did not actually dream about the game itself.

The amnesia patients did not remember playing the game andthey did not ever improve, unlike the volunteers with normalmemory. Three of them did report the strange dreams, however.

What You Did vs. What You Like

“What these results, especially from the amnesics, tells usis that when the brain puts dreams together, it does it withoutknowledge of and access to memories of actual events in ourlife,” Stickgold said.

“We have two different memory systems. The hippocampalcodes information on events from our lives. So when I ask youwhat did you have for breakfast, you go to the hippocampus forthe answer,” he added.

“A second system is the neocortical,” he said, referring toanother area of the brain.

“So when I ask you when we go out for breakfast ‘what doyou like for breakfast?’ that is a different type of question.When you go for that general information you go to neocortex.An amnesic can tell you what they like for breakfast. Theycan’t tell you what they had for breakfast.”

This is because their hippocampus is damaged. The findingssuggest that the brain does not go to the hippocampus to getimages for dreams, but to the long-term, neocortical system,the researchers said.