How young finches know which songs to mimic

The researchers isolated two different types of neurons in young songbirds: ones that were activated only when the birds heard themselves singing and others that were activated only when the birds heard the songs of adult birds that they were trying to imitate. (Credit: Alfonso Jr./Flickr)

Scientists have discovered the neurons that let juvenile songbirds recognize the vocal sounds they’re learning to imitate.

These neurons encode a memory of learned vocal sounds and form a crucial (and until now only theorized) part of the neural system that allows songbirds to hear, imitate, and learn its species’ songs—just as human infants acquire speech sounds.


“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,” says Sarah Bottjer, senior author of an article on the research in the Journal of Neuroscience.

“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.”
Refining the song

The discovery will allow scientists to 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.

Because this brain-behavior system is thought to be a model for how human infants learn to speak, 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.

Bottjer, professor of neurobiology at the University of Southern California, collaborated with lead author Jennifer Achiro, a graduate student, to examine the activity of neurons in songbirds’ brains using electrodes to record the activity of individual neurons.
Two sets of neurons

In the basal ganglia—a complex system of neurons in the brain responsible for, among other things, procedural learning—Bottjer and Achiro were able to isolate two different types of neurons in young songbirds: ones that were activated only when the birds heard themselves singing and others that were activated only when the birds heard the songs of adult birds that they were trying to imitate.

The two sets of neurons allow the songbirds to recognize both their current behavior and a goal behavior that they would like to achieve.

“The process of learning speech requires the brain to compare feedback of current vocal behavior to a memory of target vocal sounds,” Achiro says.

“The discovery of these two distinct populations of neurons means that this brain region contains separate neural representation of current and goal behaviors. Now, for the first time, we can test how these two neural representations are compared so that correct matches between the two are somehow rewarded.”

The next step for scientists 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, Bottjer says.

The National Institute of Neurological Disorders and Stroke and National Institute on Deafness and Other Communication Disorders supported the research.

Source: USC