A new study finds dreams play a role in helping the brain sort through memories.

By Maggie Fox
The Associated Press
Oct. 14, 2000

A study involving people with amnesia, a popular computer game and sleep experts may help explain why dreams are so weird and so important, experts said Thursday.
They said people with amnesia who played the popular computer game Tetris dreamed about the images it invoked, but could not remember actually playing the game. And, unlike people with normal memories, they never really got any better at the game.

Subconscious Filing
This shows that when the brain is filing away the memories it needs to keep, it has to go through a series of steps, and dreaming is a manifestation of one crucial step, Dr. Robert Stickgold, 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 it in the right place,” Stickgold said in a telephone interview.
“A lot of REM [rapid eye-movement] dreams, those really quirky, strange, bizarre dreams that we have late at night, is the brain looking for ways to cross-index. It is looking for cross references — does this fit with this? Sometimes it does and sometimes it doesn’t,” he said.
When it doesn’t fit, the dream seems weird, he said. When the cross-reference is a good one, the brain can reinforce the memory.
One way to test this is to look at people who are missing one of those vital memory steps — people with amnesia.

Tetris on the Brain
Stickgold had noticed that when he skied, he had vivid dreams about it.
“When you go downhill skiing, when you go to sleep, you can feel the turns,” he said. This would make a good test, he said, but added he knew he would never get the OK to take first-timers downhill skiing for a scientific experiment.
And then someone mentioned Tetris, a computer game that uses vivid images of falling and rotating shapes that have to be 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, Stickgold and colleagues said nearly two-thirds of the 27 volunteers they asked to play Tetris had dreams about it.
Their group included five people with amnesia, caused by disease, stroke and other accidents. Experts at the game and first-time players were also tested.

People in both groups reported that, as they fell asleep, they dreamed about images of blocks falling and rotating, as they 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 and they did not ever improve, unlike the volunteers with normal memory. Three of them did report the strange dreams, however.

What You Did vs. What You Like
“What these results, especially from the amnesics, tells us is that when the brain puts dreams together, it does it without knowledge of and access to memories of actual events in our life,” Stickgold said.
“We have two different memory systems. The hippocampal codes information on events from our lives. So when I ask you what did you have for breakfast, you go to the hippocampus for the answer,” he added.
“A second system is the neocortical,” he said, referring to another area of the brain.
“So when I ask you when we go out for breakfast ‘what do you 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. They can’t tell you what they had for breakfast.”
This is because their hippocampus is damaged. The findings suggest that the brain does not go to the hippocampus to get images for dreams, but to the long-term, neocortical system, the researchers said.

Copyright 2000 The Associated Press.

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