Oxytocin plays key role in zebra finch song learning

A recent study conducted by neuroscientists at Emory University suggests that oxytocin, commonly known as the “love hormone,” plays a crucial role in the process of how young zebra finches learn to sing by imitating their elders. The findings, published in Scientific Reports, contribute to our understanding of the neurochemistry underlying social learning.

The study’s first author, Natalie Pilgeram, a Ph.D. candidate in psychology at Emory University, states, “We have discovered that the oxytocin system is involved from an early age in male zebra finches’ learning of songs. This fundamental research may provide insights into the mechanisms of vocal learning not only in birds but also across the animal kingdom, including humans.”

Donna Maney, a professor of neuroscience in Emory’s Department of Psychology and the senior author of the study, adds, “Our findings indicate that the neurochemistry involved in early social bonds, especially during language acquisition, may have implications for studying autism.”

Young male zebra finches learn to sing by listening attentively to an adult male tutor, typically their biological or foster father who nurtures them. This social learning process shares similarities with how children acquire speech, making these birds a valuable model for studying the neural mechanisms of social vocal learning.

The researchers demonstrate in their study how oxytocin, a hormone crucial for social bonding, influences young finches exposed solely to the songs of unfamiliar males. Through experiments, when the oxytocin receptors of the young birds were blocked while they listened to a particular male’s song, the birds showed a bias against that male’s song. Conversely, when the birds’ oxytocin receptors were allowed to function normally, they preferred to listen to and eventually learn the song of a different male.

This research builds upon previous work conducted by the Maney lab, which explores the hormonal and genetic factors influencing social behavior. The lab collaborates with researchers at the Marcus Autism Center in Atlanta to maximize the potential translational impact of their research findings.

Finding their voice

Zebra finches are highly sociable birds that form large colonies in the wild. Among them, only adult males engage in singing, primarily to attract females during courtship.

From the moment they hatch, male zebra finches begin actively listening to songs and memorizing specific tunes, even before they are capable of producing their own. “Until around day 50, they emit soft chirps and warbles, which we refer to as ‘subsong’,” explains Pilgeram. “It’s similar to human infants who start babbling around six months of age before they can speak.”

During this critical listening phase, a male zebra finch pays utmost attention to the song of its father, even though it can hear the songs of other adult males in the vicinity.

In a controlled laboratory setting, studies have revealed that if the biological father is removed from the cage before the male hatches and replaced by an interacting “foster father,” the young male will exhibit a preference for the foster father’s song over that of other males. This preference is demonstrated by the young males pressing levers that allow them to listen to playback of different songs.

Learning from their environment

“The young birds have an insatiable desire to absorb information from their environment,” explains Pilgeram. “Similar to human development, these birds pay the utmost attention to their primary caregivers, upon whom they depend for everything.”

Around day 50, the young male finches enter a crucial phase known as the “plastic song phase.” During this period, they actively practice their motor skills required for singing and make deliberate attempts to produce songs. While their focus starts to shift away from their fathers, and they develop a preference for hearing the songs of other males, each young male continues to practice and refine their father’s melody.

By day 100, most male zebra finches have fully mastered their father’s song. They have reached adulthood, and their own unique rendition of the song has “crystallized” into the vocalization they will sing throughout their lives.

Previous research conducted by the Maney lab revealed an intriguing correlation: the stronger the preference a male zebra finch demonstrates for its father’s song during the early listening phase, the more closely its adult song will resemble that of its father.

The role of oxytocin

In the current study, the researchers aimed to investigate whether the oxytocin system influenced the preference for a specific song in young male zebra finches.

The study focused on male juvenile zebra finches that were hatched and raised in a laboratory setting. When the birds reached day four, their fathers were removed from their cages, and they were exclusively nurtured by their mothers. The cages were placed in chambers designed to isolate the young birds from hearing the songs of other birds housed nearby.

Starting from day 27 of the young birds’ lives, they underwent a series of tutoring sessions conducted by two adult male tutors whom they had never heard before. The tutor’s cage was positioned next to the young bird’s cage, also known as the pupil. During exposure to one of the tutors, the pupil received a substance that blocked the activation of its oxytocin receptors. For the other tutor, the pupil received a control substance that allowed its oxytocin receptors to function normally.

Following the completion of the tutoring sessions, the pupils were presented with two different levers within their cages. Pressing one lever had a higher likelihood of playing the song they heard when their oxytocin receptors were blocked, while the other lever was more likely to play the song they heard with normally functioning oxytocin.

The results demonstrated that during the early stages of their development, the juvenile zebra finches showed a preference for the song they heard when their oxytocin receptors were not blocked.

Building on past findings

The study also revealed that when the oxytocin receptors were not blocked, the developmental patterns of the birds aligned with the data curve observed in previous research conducted by the team. The young finches exhibited an initial preference for one tutor’s song, which later shifted during puberty to preferring the song of the other tutor.

As the birds began to sing their chosen tutor’s song, their preference plateaued. The strength of their preference for the chosen tutor’s song during the early listening phase correlated with the similarity of their own adult song to that of the chosen tutor.

Furthermore, the researchers observed behavioral differences in the interactions between the pupils and tutors. When the oxytocin receptors were functioning normally, the pupils displayed more frequent pecking at the wall of their cages facing the tutor and engaged in preening behavior associated with focused listening in the birds, compared to when their oxytocin receptors were blocked.

“Our findings suggest that the oxytocin system plays a role in guiding early attentional focus in animals,” notes Pilgeram.

Additional authors of the study include Carlos Rodríguez-Saltos, who obtained his doctorate from Emory and is now affiliated with Illinois State University, postdoctoral fellow Nicole Baran, research technicians Matthew Davis and Erik Iverson, and Emory undergraduates Sumin Lee, Emily Kim, and Aditya Bhise.

Source: Emory University

Leave a Comment