How do baby birdies learn to sing? By babbling
WASHINGTON (Reuters) - Baby birds babble much like human infants do, and they have their own special brain circuits to do it, researchers reported on Thursday.
Their findings suggest that learning to sing -- and also to speak -- is a process independent of adult singing or speech.
Perhaps other aspects of infant learning are equally independent in the brain, Michale Fee of the Massachusetts Institute of Technology and colleagues suggested.
"Young birds learn their songs in a series of stages. They start out just as humans do, by babbling," Fee said in an audio interview on the Web site of the journal Science, which published the findings.
Listen to a baby bird babble http://int1.fp.sandpiper.net/reuters/editorial/images/20080501/b abbling.wav
Listen to an adult bird http://int1.fp.sandpiper.net/reuters/editorial/images/20080501/a dult.wav
"The brain really learns how to use its body by making spontaneous movements and seeing what happens," Fee added.
"Babbling in songbirds is just an example of play -- it's vocal play."
Fee's team has been studying zebra finches, using a system that allows them to record the firing of individual neurons in the birds' brains. They were selectively inactivating brain cells in an area called the high vocal center or HVC.
"Scientists have been inactivating this area, the HVC, for a long time to try and figure out what it does," Fee said.
They found by accident that when the HVC was inactivated, an adult bird started babbling like a juvenile.
Adults finches, he said, produce a precise, stereotyped pattern of sound.
"Every time he sings his song, he repeats that motif over and over again," Fee said. In contrast, baby birds babble randomly.
The HVC acts like a clock to produce this precision. What Fee's team learned was that the baby birds use a very different circuit when they babble.
Scientists had thought that learning to sing produced a gradual maturing of one circuit in the brain. This finding contradicts such common wisdom, and may apply to other forms of learning among baby creatures.
"I think our experiments are really the first to look at this question of where the brain circuits are that generate early vocalization in young animals," Fee said.
Other researchers have shown that when birds sing, they use areas of the brain analogous to those used in human speech. Researchers have also shown that birds not only dream, but they dream about singing.
(Reporting by Maggie Fox, Editing by Sandra Maler.)