Tuesday, July 7, 2009

How Do Songbirds Get It Right?

meadowlark (photo by JHY)
from a news release of Massachusetts Institute of Technology, "Songbirds reveal how practice improves performance", July 6, 2009

Learning complex skills like playing an instrument requires a sequence of movements that can take years to master. Last year, MIT neuroscientists reported that by studying the chirps of tiny songbirds, they were able to identify how two distinct brain circuits contribute to this type of trial-and-error learning in different stages of life.

Now, the researchers have gained new insights into a specific mechanism behind this learning. In a paper being published in the Proceedings of the National Academy of Sciences during the week of July 6, the scientists report that as zebra finches fine-tune their songs, the brain initially stores improvements in one brain pathway before transferring this learned information to the motor pathway for long-term storage.

Young zebra finches learn to sing by mimicking their fathers, whose song contains multiple syllables in a particular sequence. Like the babbling of human babies, young birds initially produce a disorganized stream of tones, but after practicing thousands of times they master the syllables and rhythms of their father's song. Previous studies with finches have identified two distinct brain circuits that contribute to this behavior. A motor pathway is responsible for producing the song, and a separate pathway is essential for learning to imitate the father. This learning pathway, called the anterior forebrain pathway (AFP), has similarities to basal ganglia circuits in humans.

On a particular day, after four hours of training in which the birds learned to raise the pitch, the researchers temporarily inactivated the AFP with a short-acting drug. The pitch immediately slipped back to where it had been at the start of that day's training session — suggesting that the recently learned changes were stored within the AFP.

But over the course of 24 hours, the brain had transferred the newly learned information from the AFP to the motor pathway. The motor pathway was storing all of the accumulated pitch changes from previous training sessions.

Listen to the birds adjust the pitch of their song atMIT
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