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A Bird Brain Idea
Researchers reveal the creative source of song in the zebra finch
By Tracy Staedter

Many animals vocalize, but most of them seem to do it by instinct. Only a few--humans and songbirds among them--learn their languages by imitation. How human babies go from babble to chatter has been poorly understood. But recently Michale Fee, associate professor of neuroscience and investigator at MIT's McGovern Institute for Brain Research, reported that he discovered a region of the zebra finch's brain that is responsible for the experimental babble of nestlings that eventually leads to their signature mating song.

Not only does this work reveal much about the finch's talent for mimicking vocalizations, but it could also shed some light on how humans do the same thing. The bird brain circuit involved is analogous to the human brain's mysterious basal-ganglia circuit, which could have something to do with learned speech.

From previous work on the zebra finch--a good songbird to study because it sticks to one mating song--Fee knew that a different section of the finch's brain, one that controls motor function, was able to produce a stereotypically patterned song, like a repetitious baseline. But that didn't explain the early talent for creative riffing that the bird displayed.

When zebra finches are about 40 days old, they begin singing random notes. At around 50 days, they start refining their song, and by the 90th day, they have it nailed. Using a drug that inhibits neural activity, Fee blocked the part of the brain that he suspected governed the creative experiments in birds about 55 to 80 days old. Usually finches that age sing capriciously, but after the injection, their songs became significantly less variable. The team concluded that the neural noisemaker was essentially feeding random notes to the previously identified motor-function part of the brain, which over time eventually found the right combination.

What's more, Fee's team found that random bursts from neurons in the noisemakers of normally developing birds coincided with new riffs in the birds' song. "The young birds are actually learning their song by trial-and-error exploration," says Fee.

"It's beautiful behavior and very relevant to speech development in people," says behavioral neuroscientist Ofer Tchernichovski of City College of New York, an expert on vocal learning in zebra finches who is familiar with Fee's work.

Now scientists have to figure out how the brain rewards the creative fluctuations that turn baby birds' babble into come-hither melodies.