Study: Rats Dream About Running Mazes

B O S T O N, Jan. 24, 2001 -- Some rats apparently can't ever escape the rat race,even when they're sound asleep.

Researchers at the Massachusetts Institute of Technology saythey've entered the dreams of rats and found them busily workingtheir way through the same lab mazes they negotiated during theday. It's evidence not just that animals dream — most pet owners knowthat — but that they have complex dreams, replaying events much theway humans do, researchers said. And they may use their dreams tolearn or memorize. The discovery, announced today, could eventually helpresearchers understand how the human mind works in the murky worldof the subconscious. "It's really opening a new door into the study of dreams,"said Matt Wilson, associate professor at MIT's Center for Learningand Memory, and lead researcher of the study, reported in Friday'sissue of the journal Neuron. "It's not just a step forward, it's astep into a new domain."

Right Results, Wrong Specifics?

But Robert Stickgold, assistant professor of psychiatry atHarvard Medical School, said that while Wilson's research providesimportant evidence of sleep's role in memory, there's no way toprove MIT researchers were seeing rats dream. That's because the link between the rats' brain patterns andactual dreaming can't proved, he said. "He's got the right results, he's just got the wrong species,"Stickgold said. "If the rat would tell us, 'Yes, I was dreamingabout running around the track,' then we'd have it nailed down." "This is a good as it can get at this point," he added. The four-year study initially focused on memory, withresearchers measuring brain activity of rats during various tasks.But after Wilson checked the rats' brain activity while sleeping,he found nearly identical brain patterns in dreaming and wakingstates. "At that point, it was kind of like a lightning bolt," hesaid.

Dreaming About the Rat Race?

For the next two years, researchers worked to prove theimplications of the initial observation — that the rats weredreaming about their daily experiences. The rats were hooked up to a device that measured the pattern ofneurons firing in the hippocampus, an area of the brain known to beinvolved in memory. The scientists had the rats perform specifictasks in a maze which produced very distinctive brain patterns. When they repeatedly saw almost exactly the same patternsreproduced during sleep, they concluded the rats were dreamingabout running through the maze. The correlation was so great that scientists said they couldplace where in the maze the rat was dreaming it was — and even ifit was dreaming of running or walking. The discovery of similarities between human and animal dreamsenables scientists to use the rats to learn more about the humanmind, Wilson said. Scientists can manipulate the rats' experiencesin a way that's not permissible with people, and shed light on oldtheories, he said. For instance, some scientists believe people solve problemsduring sleep by synthesizing related experiences in a single dream,then learning from what the experiences have in common. The theorycould be tested by exposing rats to multiple related experiences,he said.

Sleep’s Role in Memory

Scientists also believe that dreams help form and reinforce long-term memories. Stickgold said the fact the MIT rats were replayingmemories in their minds — whether they were dreaming or not —proves how important sleep is to memory. "This is exciting because we're just starting to crack thenugget of sleep's role in memory," he said. Wilson said it's a long way from watching rats dream about mazesto arriving at elusive conclusions about how the mind works duringsleep. "It will definitely be a challenge," he said. "But we have apretty good idea of what is possible." Wilson's research is funded by the National Institutes of Healthand the RIKEN-MIT Neuroscience Research Center.

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