Zebra finches develop their signature song by improvising on the initial syllable learned by mimicking their father. Photo by MIT News
BOSTON, Nov. 30 (UPI) -- Neuroscientists at MIT have detailed the song-learning process by studying the brains of zebra finches, a small Australian songbird.
In the first two weeks of life, young birds progress from baby-like babbles to repetition of a distinct syllable. This syllable is then varied slightly to form other syllables, until the bird has acquired a repertoire of three to seven syllables. Strung together, these syllables form the bird's signature song.
Researchers monitored the birds brains during their learning process, watching as an original string of neurons were first triggered to form the first syllable and then repurposed as a new neural pathway is fixed for each new syllable.
The research is detailed in a paper, newly published in the journal Nature.
Previously, researchers at MIT identified a part of the bird brain, made up of so-called HVC neurons, essential to singing. Their research into the songs of adult birds showed a short burst of activity -- 10 milliseconds or less -- during the singing of their one-second songs.
The latest experiment shows how the pathways among a bird's HVC neurons are established during each bird's formative years, from an initial sequence to a few varied patterns. The birds learn the initial sequence by mimicking their father's song.
"From that short sequence it splits into new sequences for the next new syllables," Emily Mackevicius, an MIT graduate student and one of the authors of the new paper, said in a press release. "It starts with that short chain that has a lot of redundancy in it, and splits off some neurons for syllable A and some neurons for syllable B."
Scientists say the neural mechanism detailed in their latest work likely resembles the way timing-dependent motor skills are acquired by most animals. A human, for example, may adapt neural pathway formed for a tennis stroke when later learning a ping pong stroke.
"This is a very natural way for motor patterns to evolve, by repeating something and then molding it, but until now nobody had any good data to understand how the brain actually does that," Ofer Tchernichovski, a professor of psychology at Hunter College who did not participate in the study, told MIT News. "What's cool about this paper is they managed to follow how brain centers govern these transitions from simple repetitive patterns to more complex patterns."
The mechanism may also explain how genes are duplicated for new-but-related functionality over the course of evolution.
"If you duplicate a gene, then you could have separate mutations in both copies of the gene and they could eventually do different functions," said Tatsuo Okubo, a former MIT graduate student and lead author of the new study.
"It's similar with motor programs. You can duplicate the sequence and then independently modify the two daughter motor programs so that they can now each do slightly different things."