Young songbirds babble before they learn to sing

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Washington, May 4 (UNI) As human babies babble before they learn to speak so do the young songbirds before they mimic an adult's song.

''The babbling during song learning exemplifies the ubiquitous exploratory behavior that we often call play but that is essential for trial-and-error learning,'' comments Michale Fee, the senior author of the study and a neuroscientist at MIT, Science Daily reported.

Early on, baby zebra finches produce a highly variable, babbling song. They practice incessantly until they can produce the stereotyped, never-changing song of adults.

''This early variability is necessary for learning, so we wanted to determine whether it is produced by an immature adult motor pathway or by some other circuit,'' Fee explains.

Past research has shown that the zebra finch has two distinct brain circuits dedicated to song, one for learning and another -- known as the motor circuit -- for producing the learned song.

Damage to the first circuit while the bird is still learning prevents further learning, so the song remains immature. Yet in an adult that has already learned its song, disabling the learning circuit has no effect on song production.

When they disabled a part of the motor circuit known as HVC in these very young birds, the babies continued to sing, implying that some other brain region produces the babbling.

The authors suspected that a key component of the learning circuit, called LMAN, has a previously unknown motor function. They confirmed this by showing that when LMAN was disabled in very young birds, they ceased babbling.

''This tells us that singing is driven by two different motor circuits at different stages of development,'' explains Aronov.

''We've long known that these two pathways develop physiologically at different times, so there's an elegant parallel between our functional findings and what is already known about anatomy, he added.

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