A team of scientists at the University of Southern California say they have discovered a population of neurons in the brains of juvenile songbirds that are necessary for allowing the birds to recognize the vocal sounds they are learning to imitate. These neurons encode a memory of learned vocal sounds and form a crucial part of the neural system that allows songbirds to hear, imitate, and learn its species’ songs, in a manner similar to human infants acquiring speech sounds.
“We report the discovery of two distinct populations of neurons in a cortico-basal ganglia circuit of juvenile songbirds (zebra finches, Taeniopygia guttata) during vocal learning: (1) one in which neurons are selectively tuned to memorized sounds and (2) another in which neurons are selectively tuned to self-produced vocalizations,” write the scientists in the current issue of The Journal of Neuroscience. “These results suggest that neurons tuned to learned vocal sounds encode a memory of those target sounds, whereas neurons tuned to self-produced vocalizations encode a representation of current vocal sounds.”
The scientists believe their discovery will help uncover the exact neural mechanisms that allow songbirds to hear their own self-produced songs, compare them to the memory of the song that they are trying to imitate, and then adjust their vocalizations accordingly.
This brain-behavior system is thought to be a model for how human infants learn to speak, so understanding it could prove crucial to future understanding and treatment of language disorders in children. In both songbirds and humans, feedback of self-produced vocalizations is compared to memorized vocal sounds and progressively refined to achieve a correct imitation.
“Every neurodevelopmental disorder you can think of, including Tourette syndrome, autism, and Rett syndrome, entails in some way a breakdown in auditory processing and vocal communication. Understanding mechanisms of vocal learning at a cellular level is a huge step toward being able to someday address the biological issues behind the behavioral issues,” said Sarah Bottjer, Ph.D., senior author of the article entitled “Neural Representation of a Target Auditory Memory in a Cortico-Basal Ganglia Pathway”.
The next step for study will be to learn how the brain rewards correct matches between feedback of current vocal behavior and the goal memory that depicts memorized vocal sounds as songbirds make progress in bringing their current behavior closer to their goal behavior, said Dr. Bottjer.
