For both people and songbirds, communication begins in the brain. Researchers at the University of Texas Southwestern are exploiting that similarity by studying young zebra finches in order to uncover the exact neural connections that underpin how we learn language. Their work, including their most recent study published last month in Nature Neuroscience, provides hope we could someday learn how to protect these connections in people at risk of developing speech disorders.
"Remarkably, many of the genes that have been identified in humans that affect speech development also seem to have strong parallels in their effects on song development in birds," explains Todd Roberts, head of the songbird lab at the UT Southwestern Medical center.
In their latest study, the team used imaging methods to look into the brains of juvenile finches as they learned how to vocalize their first songs. As expected, they found that connections between neurons in the motor and auditory cortex of the brain were involved. They also seemingly discovered a unique type of neuron responsible for transmitting vocal motor signals to the auditory cortex. Young birds that were genetically modified to lack these neurons were worse at mimicking the songs of their adult mentors, a key component of learning language, further suggesting their importance.
"Songbirds actually learn their songs by imitating the song of their fathers or other adult birds of the same species and then they go through an extended phase of vocal practice where they'll practice their song upwards of a hundred times during development," Roberts says. The same principle holds true for us, though instead of songs, it's baby babbles. We imitate the sounds and words we hear from our parents and siblings while gradually learning to correct ourselves when it doesn't match up.
More From Tonic:
But in children with speech disorders, this process is hampered—indeed, one of the hallmarks of autism spectrum disorder is an inability to imitate others as infants, which then contributes to learning and speech disabilities later on in life. An estimated 3.5 million Americans live with autism currently, according to research cited by the Autism Society, while one in every 68 children born today develop it in their early childhood.
By understanding and mapping the brain circuits involved in learning and controlling speech, Roberts and his team hope to gain insight on how to eventually repair them, for instance, by targeting the genetic quirks and mutations linked with these flaws in the womb.
"This new study is revelatory in the sense that it pinpoints a brain circuit long speculated to perform important computations involved in speech learning and provides the first proof that this circuit is critical to learning vocal behaviors," he says. The neurons may play a role in adults' brains too. When the team knocked them out in adult finches, the birds could still remember the songs they had learned, but couldn't change their tempo or pitch.
Roberts' team isn't the only group using songbirds as a model for human speech development—scientists at Florida State University recently obtained a $800,000 grant from the National Science Foundation to expand their work with songbirds. And other teams have used zebra finches to study neurodegenerative disorders that lead to speech loss like Huntington's disease.
Read This Next: Is This What Consciousness Looks Like?