Birds in the brain scanner – When pigeons dream: Similar sleep patterns to humans – Knowledge


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A sleep study with pigeons brings astonishing things to light: not only mammals, but also birds are very likely to dream. The researchers even suspect that they dream of flying. The findings could also advance Alzheimer’s research.

Pigeons don’t necessarily have the best reputations: their droppings can damage buildings, and they cause mess and expense, especially in cities. Brain researchers see things differently. You could already prove that pigeons are cognitively on the ball: They have a phenomenal sense of direction and are hard-working and persistent. And now it turns out that you can even dream.

Human attributes

All qualities that are also found in humans. Researchers were able to measure the latest parallel to humans in a brain scanner, such as a study reported in the journal “Nature Communications”: Pigeons sleep very similarly to humans. Bird sleep patterns look amazingly similar to ours. And: pigeons probably dream too.

Pigeons in the brain scanner


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For the study by the Ruhr University Bochum and the Max Planck Institute for Biological Intelligence, the research team accustomed 15 laboratory pigeons to sleeping in a brain scanner. They were then able to record their brain activity and pupil movements while they slept. To do this, the researchers used a breed of pigeon that has transparent eyelids: the Budapest pigeon. This made it possible to film their pupils even when their eyes were closed.

In humans, intense, emotional dreams take place during the REM sleep phase. REM stands for rapid eye movement. And the researchers were also able to identify such phases in pigeons.

Compared to mammals, the dream phases in the test pigeons were shorter, mostly under ten seconds. But they came up very often, in hundreds of dream episodes a night.

In addition, the pupils of the pigeons became suddenly smaller during sleep. This happens when the pigeons are awake, when they become aggressive or when they are courting. And suggests that birds also experience feelings in their dreams.

The dream of flying

The assumption that the pigeons are dreaming was made by the researchers based on brain scans (see info box). And interpret the results as follows: It is “tempting to speculate that our pigeons could have dreamed of flight scenes,” says the scientific article. Because in their presumed dreams, the same brain regions are active as when they fly: the pigeons process visual stimuli and navigation information.

Long history of dreaming

The results suggest that dreaming has a very long history. “The last common evolutionary ancestor of birds and mammals lived around 315 million years ago and thus dates back to the early days of terrestrial vertebrates,” says Onur Güntürkün, one of the authors of the article.

Sleep is essential for a healthy brain

Quite apart from the dreams, the results are interesting for another reason. It has been known for several years that a kind of dishwasher for the brain is activated during sleep. This eliminates harmful proteins that are involved in the development of Alzheimer’s, among other things. To do this, cerebrospinal fluid is flushed through the brain. This process takes place in a sleep phase without intense dreams and rapid eye movements (non-REM phase).

The study examined this flushing process in birds for the first time. In the test pigeons, flushing fluid decreased drastically when the birds switched from non-REM to REM dreaming phases. In the dream phases, the dishwasher starts to stutter.

The change between the two phases is much faster and more frequent in pigeons than in mammals, which could increase the efficiency of the “brain washer”. These results could be instructive for understanding the corresponding processes in humans. And possibly help to decipher the role of the flushing process in the development of Alzheimer’s.

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