Learning to Sing, Learning to Speak

The babbling and cooing that babies do during the first months of life might be dismissed as nonsense sounds, but not by Teresa Nick, a neuroscience researcher at the University of Minnesota. 

Babbling, she says, is important work babies must do to learn to use their voice box, tongue, breath, and lips to eventually say words. During the “babbling” phase an intricate, but poorly understood, interplay is occurring between what the baby hears in her environment, what the baby hears herself say, and special clusters of cells in the brain. This phase is a precious window of opportunity for vocal learning during which Nick says the brain can be likened to moldable clay and the environment to a potter shaping the clay -- the brain’s cells and learning pathways -- until recognizable words emerge.

To better understand what is going on in the brain during vocal learning, Nick is studying how the male zebra finch learns its distinctive song. Her research is supported by funding from several sources, including one of the National Institutes of Health, the National Institute on Deafness and Other Communication Disorders. Songbirds are among the few creatures in the animal world that learn a complex vocal pattern. In this, they are like people. Insights into their brains may, in the long run, help children who have a hard time learning language or are diagnosed as autistic.

Since beginning her study of zebra finches in 2003, Nick has discovered an electrical pattern produced by the baby zebra finch’s brain that shows when the window of learning opportunity is open and when it closes.

Nick, a 2005 recipient of a four-year award from the John Merck Scholars Program in the Biology of Developmental Disabilities in Children, hopes this finding and her continued work will provide insight that could help the one in 10 children who has a developmental disability involving speech.

To investigate brain activity in a baby zebra finch’s brain as it babbles, Nick implants electrodes into the song-producing area (or vocal-learning center) of its brain. These electrodes record brain cells’ electrical activity for several weeks while the bird sleeps, while it listens to the song it will learn, and while it babbles and learns the zebra finch song. Nick simultaneously records the bird’s baby talk.

She has found that as the baby finch learns its song, it continuously changes the tune until it matches the signature song of the zebra finch. Day by day, the bird gets better at singing the song. And, while this happens, the electrodes attached to the song-producing area of the brain offer an electronic illustration of what’s going on in the brain.  

During songbird babbling, there is a great deal more electrical brain-cell chatter in the vocal-learning center of the baby finch compared with the adult. In adult zebra finches, the electrical brain-cell activity closely matches when the finch sings. Nick found that, in baby finches, brain cells continue firing for a period before and after the bird makes any sounds. This extended electrical activity in the brain is called “prolonged bursting.” When the critical window of learning ends, so does the prolonged bursting. 

Nick, excited about this expanded understanding of vocal learning, was further intrigued and heartened when she learned that prolonged bursting also occurs during a critical period for visual learning. Further, an Italian researcher investigating the visual-learning window found it could be reopened when the study subject was given a special drug. The reopening allowed the dominance of one eye over the other to change in the study animal, something that before was not possible.

What if the window of vocal learning could be widened or possibly reopened? Could this allow children with language and speech disabilities a second chance? That’s one hope from this scientific study.

Nick says the next step in her work will be to see if the critical period for vocal learning can also be reopened. “If the vocal-learning model is the same as the visual model, this would mean you could reopen this period of vocal learning in humans and help children with severe vocal learning problems such as those that exist in autism.”

--Jennifer La Forgia