Animals have complex dreams, MIT researcher proves

Study may advance understanding of human learning and memory.


While any pet owner knows that animals seem to dream, and studies show that animals' brains follow the same series of sleeping states as ours do, this is the first time that researchers know what animals are dreaming about.

"No one knew for certain that animals dreamed the way we do, which can involve replaying events or at least components of events that occurred while we were awake," said Matthew Wilson of MIT's Center for Learning and Memory. "We looked at the firing patterns of a collection of individual cells to determine the content of rats' dreams. We know that they are in fact dreaming and their dreams are connected to actual experiences."


"It has been a century since Freud brought forward the study of the subconscious and the examination of the content of dreams as a tool for understanding the nature of cognition and behavior in humans," Wilson said. "We now have the means to bring this world of dreams into the study of animal cognition, and by doing so, gain deeper insight into our own."

Running in circles






Not-so-instant replay




"If you learn five things when you are awake, which ones are retained?" Wilson said. He speculates that if certain bits of information are replayed during sleep, this might determine which events we then remember.

Studies have shown that humans learning repetitive tasks can use REM sleep to enhance performance. In some cases, this "off-line" practice session seems to be just as good as practicing the experience when awake. Tests have shown that both rats and humans are better at a recently learned task after a period of sleep.

Likewise, dreams may represent an opportunity for us to continue to work on a problem while we're asleep. Some people report waking up with a solution to a problem that had been puzzling them for days.

"One theory regarding the role of dreams in memory is that dreams may provide the opportunity to bring together experiences that were related, but did not occur at the same time, in order to learn from them," Wilson said. "For example, replaying a series of pleasant or unpleasant experiences may allow us to learn what these experiences had in common and use this to guide future behavior."

Animal dreams

Why do animals dream about one experience and not another? "This work allows us to evaluate the content of dreams and create tests to see which awake patterns create patterns when the animal is asleep," Wilson said. "If we are able to evaluate the content of the dreaming state, we may be able to find out why certain events get replayed and others don't."

This work also raises questions about long-held assumptions about animals' thought processes. Only a handful of species — among them chimps and dolphins — were thought to have any ability at all to recall and evaluate detailed sequences of events after they occurred. Wilson points out that "dreams are the ultimate off-line experience. This work demonstrates that animals are capable of re-evaluating their experiences when they are not in the midst of them."



Topics: Neuroscience, Biology, Brain and cognitive sciences, Picower Institute for Learning and Memory, Animals, Dreams


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