How do baby birds learn to sing?
2008-05-02 12:55
Washington - 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 website of the journal Science, which
published the findings.
"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 centre 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.
Repeated motif
"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 vocalisation 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.