Replaying the events of the day as you sleep is thought to be an important process not only for humans, but also a whole host of other animals from armadillos to lizards. While birds have been shown to dream about singing, new research has found that they even move their vocal muscles as if they are actually trilling a tune as they nap.
It is thought that the process of dreaming helps in memory consolidation. By measuring brain activity as various creatures sleep, researchers have found that all mammals, and plenty of other different species to boot, experience rapid eye movement sleep, or REM. It is at this point during slumber that a sleeper is most likely to dream vividly.
Earlier research has found that sleeping birds' neurons fire in a complex pattern similar to what is seen when the birds sing their songs during the day. This was thought to be evidence that after hearing certain songs, such as those of a young bird's parents, they continue to practice the tune even when they next take a nap.
A new piece of research, published in PeerJ, has gone one further. After surgically attaching electrodes to the vocal muscles of 10 zebra finches, a team set about recording any activity while the birds slept. They found that in addition to firing neurons as if they were singing as they dreamt, the birds also flexed their vocal muscles as if they were physically singing, too.
But while it was assumed from the brain scans that the finches were effectively replaying the songs from that day during the night, this latest work seems to suggest something else. The movements of the vocal muscles during dreaming didn’t actually match up with the movements made during the day as the birds sang.
This, the researchers suggest, could mean that the birds may not have been dreaming about their own well-versed songs – which tend to stay very similar during the bird's lifetime – but could instead be practicing other variations of their tune instead. They think that it could be a way for the brain to figure out when the bird might sing a dud note, and so help them maintain their high stereotypy during the day.
Whatever the case, it seems clear that the activity of the muscles would be enough, should an airflow be present, for the birds to sing as they sleep.
[H/T: New Scientist]