Certain songbirds have a pretty human-sounding way of learning their special tunes: They listen to their fathers.
Scientists have known that zebra finches -- one of the most oft-studied songbirds -- learn their songs by listening to their dads, but a new study published Tuesday in the journal Nature Communications takes that a step further. Researchers are hunting for the neural pathways that allow the young finches to figure out how to sing.
This may seem like pretty esoteric work, but research into song learning in birds could teach us about our own neurological development.
SEE ALSO:Drunk birds slur when they sing, tooZebra finches are a favorite of neuroscience researchers because of their intriguing song-learning behavior. While both male and female zebra finches have the ability to make various vocalizations, only male zebra finches develop a song, which they later use to attract a mate.
Up until now, scientists have suspected that a specific part of the brain helps this little bird learn and memorize the song he will use to attract a mate. However, the new research is able to demonstrate the way neurons in a particular brain region aid in the song-learning process.
Young zebra finches typically start learning their songs by listening to their fathers in the first four months of their life, said Yoko Yazaki-Sugiyama, an assistant professor and brain science expert at the Okinawa Institute of Science and Technology, and one of the study’s authors.
“The first one month or so, they don’t sing -- but they are listening to what their fathers sing,” she explained. “So a month after, they are starting to sing by themselves, but in the beginning their songs are not really matured -- more like a baby babbling. And then at that time what they’re doing is hearing their own song and trying to match their own vocals to the tutor song.”
After about 90 to 100 days of life, their songs become stable, she said.
Previous research has suggested that a specific area of the brain known as the caudomedial nidopallium, or NCM, is the place where young zebra finches store memories of the “tutor song,” or the song their fathers sing to teach them, when they hear it.
This brain region is similar to the auditory cortex found in humans, the part of the brain that helps process sound information.
“But none of these [previous] studies had shown what kind of neural activity was happening in this period,” Yazaki-Sugiyama said.
She and colleague Shin Yanagihara, also of the Okinawa Institute, decided to record neural activity in the brains of juvenile zebra finches in order to find out.
The researchers gathered 20 birds, all between 50 and 92 days old, and exposed them to nine different types of sound stimuli. These included a tutor song, as well as recordings of the young birds’ own singing and songs from other species.
After exposure to the different stimuli, the researchers found that a certain subset of neurons in the NCM became selective -- from that point on, they would only fire in response to a certain type of song.
The majority of the neurons that did so became selective to the tutor song, although a few of them became selective to other stimuli, such as the baby bird’s own vocalizations.
This activity suggested that these neurons were critical to storing memories of specific types of sounds.
A zebra finch.Credit: Andia/UIG via Getty ImagesInterestingly, the researchers found that as the young finches practiced and perfected their own songs, there was not much change in the number of neurons that were selective for the tutor song over time.
This suggested that the neurons’ selective nature was driven by simply hearing the tutor song in the first place, rather than working on it themselves -- otherwise, as the birds practiced and improved their songs over time, the researchers would have expected to see the number of selective neurons increase.
It’s possible this type of research could even help lay the groundwork for later studies on human development
In this way, the results supported the idea that these neurons were really responding to hearing the tutor song, and not the young bird’s attempts at developing his own song.
The researchers were also able to demonstrate that the selectivity of these neurons lessened -- that is, the neurons were more likely to respond to other stimuli -- if the researchers interrupted the flow of certain chemicals in the brain that naturally help groups of connected neurons (what’s known as a “neural circuit”) communicate with one another.
Via GiphyThey also observed a decrease in selectivity while the birds were asleep.
These observations suggest that the behavior of selective neurons is still dependent on certain conditions in the brain, such as the health of neural circuits.
A bird that experiences trauma or damage to this part of its brain might have trouble forming these types of memories, for instance.
In the future, Yazaki-Sugiyama hopes that these findings can help inform additional research on how the birds’ early experiences might affect their cognitive functions later in life.
And she noted that it’s possible this type of research could even help lay the groundwork for later studies on human development and the learning of languages.
At the very least, the study demonstrates that there’s still much we can learn from one of nature’s most beloved phenomena.
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