Young songbirds rehearse their songs in their sleep, American researchers have found, and they say this could have implications for our understanding of how children learn to talk.
Daniel Margoliash and Amish Dave at the University of Chicago recorded the firing patterns of neurons in the brains of young Australian zebra finches. He found that patterns the birds produced while they were awake and singing were repeated with very slight variations while they were asleep.
鈥淭he young zebra finch appears to store the neuronal firing pattern of song production during the day and reads it out at night, rehearsing the song, and perhaps improvising variations,鈥� Margoliash says.
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鈥淢y sense, from this and other research, is that we鈥檙e gaining an insight into a mechanism that is very general across animals,鈥� he adds.
The research supports the idea that certain sleep processes are important for learning, says Margoliash. He thinks it鈥檚 鈥渉ighly probable鈥� that people learning a task will show the same rehearsal patterns during sleep as the zebra finches.
Margoliash is planning studies on people to investigate this. And further studies on the young finches should reveal whether disrupting their night-time rehearsals will disrupt their song acquisition.
Song acquisition is often used as a model for how children learn their first language. And Margoliash鈥檚 results with the sleeping zebra finches suggest that talking to babies while they sleep will not help them learn to speak.
Margoliash surmised this by playing the young sleeping birds recordings of their own songs, and songs of other birds. Zebra finches sing only one song, but the pattern varies slightly between indidividual birds.
When the birds heard their own song in their sleep, they produced precisely the same pattern of neuronal firing as when they were awake and singing. But the birds showed no response to recordings of other birds鈥� songs.
This suggests that children learning to speak, or adults learning a new language, may not respond to other people鈥檚 voices while they sleep, Margoliash says.
The data from sleeping birds is also important for our understanding of how sleep may help animals learn a task, says Margoliash.
There is a brief delay between the neuronal firing that leads to the physical production of a pattern of notes and the bird actually hearing itself making the sound. So by the time the bird hears the sound, its 鈥榮ong-production鈥� neurons are already producing different notes.
That raises the question: how does the bird identify the pattern of neuronal firing that produces the 鈥渞ight鈥� sound, so that it can learn to reinforce it?
Every animal learning a task that involves integrating information from the senses and movement faces the same problem. Margoliash thinks that this is where the birds鈥� night-time activities come in.
鈥淚t seems that by storing the song production pattern and reading it out at night the bird has an 鈥榦ffline鈥� solution to the timing problem,鈥� he says. 鈥淭his means the zebra finch can replay and strengthen the pattern during sleep.鈥�