A new study suggests mice learn to sing using similar mechanisms to one ones… (China Photos / Getty Images )
Mice appear to learn to sing from other mice in a manner similar to how humans and songbirds learn, according to a new study.
Songbirds are a common model animal for studying language acquisition and learning. That's because they learn to sing from those around them, and because they have specific brain networks honed for this purpose.
Researchers have long held that a small group of animals including humans, songbirds, dolphins, whales and elephants are "vocal learners," while most animals are not. Instead, other animals have vocalizations that are innate and do not change during the animal's lifetime. Mice have always been thought to fall into this latter camp.
Male mice make song-like vocalizations as part of their mating rituals, but scientists didn’t think those songs were learned. This is in part because mice appeared to lack a key brain circuit that connects the motor control parts of the brain with the part of the brainstem that directly controls the larynx – an omission that seemed to show that their brains weren't wired right to allow such learning.
But in the new study, researchers at Duke University discovered that there is a connection between those two areas in mice that is similar to the one seen in birds. What's more, they found that it became active during singing.
But that alone is not enough to prove learning; the researchers wanted to see that disrupting the newly found circuit could cause changes to a song, as it does in songbirds. So they chemically destroyed the pathway, and observed the frequency and pitch of the song before and after doing so. While the song was not eliminated, it was markedly changed.
Another way that scientists have tested song learning in birds is to see what happens when they go deaf. When animals that produce only inborn sounds are deafened, their vocalizations stay the same. But when songbirds or humans are deafened, vocalizations change a great deal. When the researchers deafened a group of mice, they found that their songs began to deteriorate. Mice that had always been deaf could barely sing at all, showing that mice need to continue to hear their songs to keep them going -- a hallmark of learned vocalizations.
In what is perhaps the most convincing experiment of the bunch, the researchers took two strains of mice that they noticed had different sounding songs and put them together. If learning were impossible, their songs would continue to sound different. But if the mice could learn, their songs would be expected to converge, sounding more similar over time. That is what they found: The mice's songs changed frequency by thousands of Hertz, becoming more similar, showing that they were indeed learning from each other.
What do we gain from knowing mice can learn to sing from others? For one, it gives us another model for studying language learning, in mice -- a far more common lab animal than the songbird. But more generally, the finding seems likely to continue breaking down the walls we have put up between species. Just as New Caledonian crows have now been shown to be able to infer the actions of a hidden person, the ability of mice to learn songs tells us that such abilities may not be as binary as we once thought: While mice do not learn songs as well as humans or songbirds, learning does seem to play a significant role in their song over time. Or, as the authors put it, we may continue to find that "all behaviors exist along a continuum."
You can read the study here.
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