2023-06-26 12:45:29
While we sleep, our brain undergoes a complex set of processes to ensure that when we wake up having had enough sleep, we feel mentally and physically fit. In humans, different phases of sleep, essentially rapid eye movement (REM) sleep and non-REM sleep, are associated with different changes in physiology, brain activity, and cognition.
For example, during REM sleep, our brains are very active and we dream, often very vividly and emotionally.
In contrast, during non-REM sleep, the brain is metabolically less active and focuses on removing waste products through the flushing action of cerebrospinal fluid through the brain’s ventricles (the interconnected chambers that surround brain structures) and then through the brain. This process is supposed to help the body remove harmful protein deposits from the brain, such as those associated with the development of Alzheimer’s disease.
Until now, the question of whether similar processes also take place in birds has not been resolved.
A team consisting of, among others, Onur Güntürkün and Mehdi Behroozi, from the Ruhr University in Bochum (RUB), as well as Gianina Ungurean, from the Max Planck Institute for Biological Intelligence in Seewiesen, both institutions in Germany, have investigated the issue and has found answers.
To find out exactly what happens when the birds sleep, the researchers used infrared video cameras and functional magnetic resonance imaging (fMRI) to observe and record the sleep and wake states of 15 pigeons specially trained to sleep soundly under them. experimental conditions.
The video recordings allowed the researchers to observe whether one or both eyes of each pigeon were open or closed, and to follow eye movements and changes in pupil size through the pigeons’ transparent eyelids during sleep. Simultaneously, functional magnetic resonance imaging provided information on brain activation and cerebrospinal fluid flow in the ventricles.
During REM sleep, the researchers observed strong activity in brain regions responsible for visual processing, including areas that analyze the movement of the pigeon’s environment during flight. The team also observed activity in areas that process signals from the body, especially the wings. Based on these observations, the study authors believe that birds, like humans, dream during REM sleep, and that in many of their dreams, they fly.
In addition, the scientists observed the activation of a brain area known as the amygdala during this phase. Given the role of the amygdala, such activation suggests that if birds experience something similar to our dreams, pigeon dreams probably also include emotions like ours. This hypothesis is supported by the fact that the pupils of birds constrict rapidly during REM sleep, just as they do during courtship or aggressive behaviors when awake.
Pigeons also dream while they sleep. The study authors have observed them do so. (Photo: © RUB, Marquard)
As in humans, the flow of cerebrospinal fluid through the ventricles is increased during non-REM sleep in pigeons.
“The most recent common evolutionary ancestor of birds and mammals dates back about 315 million years, to the earliest times of terrestrial vertebrates. However, the sleep patterns of birds are remarkably similar to those of mammals, including REM and non-REM phases”, points out Güntürkün.
The study is titled “Wide-spread brain activation and reduced CSF flow during avian REM sleep”. And it has been published in the academic journal Nature Communications. (Source: NCYT from Amazings)
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