‘Love hormone’ guides young songbirds in choosing ‘voice coach’

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“We found that the oxytocin system is involved from an early age in learning to sing in male zebra finches,” says Natalie Pilgeram, first author of the study and an Emory psychology doctoral candidate. “It is basic science that can lead to an understanding of the vocal learning process in the entire animal kingdom, including humans.”

“Our results suggest that the neurochemistry of early social ties, particularly during language learning, may be relevant in studies of autism,” adds Donna Maney, professor of neuroscience in Emory’s Department of Psychology and lead author of the study.

Young male zebra finches learn to sing by listening to an adult male tutor to whom they choose to pay close attention, usually their biological father or a “foster” father who nurtures them. This social process has some similarities to the way that children learn to speak, making birds a laboratory model for the neural underpinnings of social vocal learning.

In the current paper, the researchers show how oxytocin, an essential hormone for social bonding, influences young finches exposed only to the songs of unknown males. In experiments, blocking young birds’ oxytocin receptors while listening to a male predisposed the birds against that male’s song. Instead, they preferred to listen to and eventually learn a male’s song that they heard when their oxytocin receptors were functioning normally.

The paper builds on previous work from Maney’s lab on hormonal and genetic influences on social behavior. Her lab is working with researchers at the Marcus Autism Center in Atlanta to maximize any potential translational impact of her research findings.

Zebra finches are highly social birds. In the wild, they nest together in large colonies. Only adult males sing, mainly to court females.

From the moment they are born, males begin to hear songs and memorize particular songs, even before they can sing one. “Until around day 50, they’re making little beeps and chirps, what we call a ‘subsong,'” Pilgeram explains. “It’s similar to human babies who start babbling around six months without actually speaking.”

During this sensitive listening phase, a male zebra finch pays close attention to his father’s song, although he may hear other adult males nearby.

In a laboratory setting, research shows that if a biological parent is removed from a cage before a male hatches and then replaced with a “foster parent” with whom they can interact, the young male will prefer singing. from the adoptive father to other males. can listen Young males demonstrate this preference by pressing levers that allow them to hear different songs being played.

“Young birds have to learn as much as they can about their environment,” says Pilgeram. “Just like during human development, birds pay the most attention to their immediate caregivers, upon whom they depend for everything.”

Around day 50, young male finches enter puberty and what is called the “plastic song phase.” During this time, they practice their song motor skills and actively try to produce songs. Although they begin to divert their attention from their parents and show a preference for listening to other males’ songs, each young male still practices the daddy tune.

By day 100, most male zebra finches are fully singing their father’s song. They have reached adulthood, and their melody has “crystallized” into the song they will sing for the rest of their lives.

In previous research, Maney’s lab found that the stronger the preference a male zebra finch displays for his father’s song during the early listening phase, the more closely his crystallized adult song will mimic that of the father.

For the current paper, the researchers wanted to test whether the oxytocin system played a role in that preference.

The research focused on juvenile male zebra finches hatched in the lab. On day four, the fathers were removed from each of the young’s cages to be reared only by their mothers. The cages were enclosed in chambers that prevented the young birds from hearing the songs of other birds housed nearby.

Starting on the 27th day in the life of a young bird, he was exposed to a series of tutoring sessions by two different adult male tutors that he had never heard of. The tutor’s cage was placed next to the cage of the young bird or pupil. When exposed to one of the tutors, the student was given a substance that blocked the activation of his oxytocin receptors. When the young bird was exposed to the other guardian, he received a control substance that allowed his oxytocin receptors to function normally.

After completing a series of tutoring sessions, the trainees were presented with two different levers that they could press on their cages. Pressing a lever was more likely to play the song they were listening to when their oxytocin receptors were blocked. The other stick was more likely to play the song they listened to with the oxytocin working normally.

The results showed that early in their development, the youngsters favored the song they listened to when their oxytocin was not blocked.

“We also found that when their oxytocin was not blocked, the birds’ developmental milestones fit the same data curve as in our previous research,” Maney says. “They showed an early preference for one tutor song, then switched to preferring the other song during puberty.”

The preference leveled off when they started singing their chosen tutor’s song, he adds. And the stronger their preference for the chosen tutor’s song was during the early listening phase, the more their own adult song resembled that of the chosen tutor.

The researchers also noted behavioral differences in the way students and tutors interacted. With oxytocin functioning normally, one student pecked more often at the wall of his cage facing the tutor and more frequently strutted in a manner known to be associated with focused listening in birds, compared to when his oxytocin it was blocked.

“Our results suggest that the oxytocin system is involved in how an animal decides where to focus its attention very early in its life,” says Pilgeram.

Study co-authors include Carlos Rodríguez-Saltos, who received his Ph.D. from Emory and is now at Illinois State University; postdoctoral fellow Nicole Baran; research technicians Matthew Davis and Erik Iverson; and Emory college students Sumin Lee, Emily Kim and Aditya Bhise.

The work was funded by the National Institutes of Health and the Silvio O. Conte Center for Oxytocin and Social Cognition.