Birds sing in their sleep, study finds

October 26, 2000
Web posted at: 3:05 PM EDT (1905 GMT)

WASHINGTON (Reuters) -- When little songbirds go to sleep, what do they dream about? Why, their songs, of course, researchers said on Thursday.

But they said their findings suggest that singing is very serious business indeed for birds -- and they can also shed light on the theory that rehearsing new skills during sleep is important in the human learning process.

"From our data we suspect the songbird dreams of singing," Daniel Margoliash, a University of Chicago biologist who led the study, said in a statement.

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"Nobody would have believed that if we study little tweetie birds, we can learn anything useful about anything," Margoliash added in a telephone interview.

"We are learning a whole lot. The field is learning a tremendous amount. (Zebra finches) are one of the premier model systems for representing how the brain manages complex information."

For their study, Margoliash and colleagues rigged up a system that would allow them to monitor individual neurons firing in the brain. Extensive study of zebra finches has shown scientists just what parts of their brains are activated when they sing.

"We have gear, an apparatus that allows us to position an electrode, a recording device, close enough to a cell so can record its activity," Margoliash said.

"It's basically a small mechanical screw that advances a small piece of wire" into the bird's brain.

It had to be very small and light so the birds would behave normally, Margoliash said. "In our case it was a particular challenge because the animal has to be free and comfortable to move about his cage."

They recorded the firing of the brain cells when the bird sang. Zebra finches are favored by biologists because they thrive in captivity and sing constant, complex songs.

"We recorded when the animal was awake, and when the animal fell asleep, we presented sounds to them," Margoliash said.

"Then we let the bird sleep in an undisturbed state and that was when we discovered the song replay."

The bird's brains fired in patterns during sleep that were very close to the patterns seen when they were singing, Margoliash's team reports in Friday's issue of the journal Science.

"If you look at the actual activity patterns when neurons burst during sleep, it is a very good match to the same neuron pattern as when they sing -- but it is not an identical match," Margoliash said.

"That is why I think they are dreaming. I think they are dreaming of their song but with variations, just as we dream of everyday experiences but in unusual ways."

Singing is serious business for birds, used to communicate in many ways, from marking territory to attracting mates. So it is important to get it right.

Margoliash plans to do more studies, and he hopes he can make the birds literally sing in their sleep.

As in humans and other animals, the brain stem shuts down movement during sleep, so that the dreamer does not act out the nightly dreams. Margoliash hopes to unhook this system so the birds would sing out loud as they dreamed.

"We would actually be able to monitor the singing of a dreaming bird," he said.

"If we can describe the rules by which sleep acts on song learning, these lessons may apply to learning in other animals, including humans. Neurobiologists have often found that lessons learned from weird and wonderful animals apply to all animals. The beautiful songs of birds could have much to teach us about how we learn."

Copyright 2000 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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