In the world of music, practice makes perfect, And the same is true of zebra finches who sing while they sleep, new research has found.
Experts have known for almost 20 years that brain patterns that control singing in the birds are present while they dream.
A previous study found that sleeping zebra finches listen to the songs of other birds while they are awake and mimic their tunes silently in their brains as they slumber.
Now, for the first time, researchers have discovered that the creatures actually move their vocal muscles in response to this process.
The finding was made by a team of physicists from the University of Buenos Aires, who attached electrodes to the vocal muscles of ten zebra finches, according to reports in New Scientist.
They found that the muscles exhibited spontaneous twitching while the bird’s slept, which matched the movements of their singing during the day.
The patterns of the muscle movements varied, suggesting the birds were practising different versions of the same song.
By playing songs to the finches while they were asleep, experts found that they could cause this nocturnal process.
They used both recordings of birdsong and digitally created versions of the tunes, although the latter were less successful.
Writing in a paper, published on the pre-print archive bioRxiv, its authors said: ‘In this work, we found that nocturnal playbacks of the bird’s own song, or synthetic versions of that song, evoke vS activity patterns strikingly similar to those recorded during song execution.’
‘During sleep spontaneous activity patterns resembling the execution pattern can be detected in vS, but not in the respiratory gesture, explaining the lack of phonation (sound)’
The only thing stopping the muscle movements producing an audible song was a lack of air, the research team says.
‘If you blew air against the syrinx [voice organ]while the bird was sleeping, you would probably hear some of these notes,’ Richard Hahnloser at the University of Zurich, Switzerland, who was not involved in the study, told New Scientist.
In October 2000, scientists published their discovery of sleep mimicry in the songbirds.
They used tiny recording devices to analyse the bird’s brain activity and found that, if the bird’s sleep is unbroken, it goes on to practise the songs, trying out variations such as changing notes or tempo.
Speaking at the time Professor Daniel Margoliash, who led the research at the University of Chicago, said: ‘From our data we suspect the songbird dreams of singing.
‘The 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.
‘The match is remarkably good.’
Professor Maroliash, whose research was detailed in the journal Science, said it suggested sleep plays a central role in the learning process.
‘If we can describe the rules by which sleep acts on song learning, these lessons may apply to learning in other animals, including humans,’ he added.
The scientists reached their conclusions by measuring the activity of individual brain cells in four zebra finches.
In the first step, they taped the sound of a bird singing and recorded the nerve- cell activity.
Then they played back the song to the same bird while it was asleep. Again they measured its brain activity and found that the pattern was identical, even though the bird produces no sound.
They even discovered the sleeping bird was able to replay the pattern slightly faster and predict the next set of notes.