The researchers tracked the brain activity of sleeping lizards.
It turns out we have more in common with dinosaurs and birds than previously thought. In the study, whose results were published last week in the journal Science, the researchers tracked the brain activity of sleeping lizards. As it turned out, sleep reptiles passes through the same phases, which are observed in mammals and birds. Apparently, so is sleeping and dinosaurs.
“The data suggests that phase of sleep in animals appeared much earlier than previously thought. The results are really surprising, because until now, scientists agree that REM and NREM sleep is characteristic only of mammals and birds. According to this view, sleep phase occurred simultaneously with the appearance of birds (about 100 million years ago), or placental mammals (about 65 million years ago)”, says Dr. Gilles Laurent Gilles Laurent, Director of the Center for the study of the brain at the max Planck Institute.
However, new data suggest that REM and NREM sleep is the common ancestor of mammals, birds and reptiles — amniote that lived about 300 million years ago, when the modern continents were part of a single spermatheca Pangaea.
The researchers implanted into the forebrain of five Agamas bearded (Pogona vitticeps) special silicon probes, which recorded the brain activity of reptiles during sleep. According to Laurent, the author used probes of a new type that more accurately tracked the status of the animal brain.
The scientists also recorded the eye movements of sleeping lizards — for this purpose we used an infrared camera and computer video analysis. Records showed that the dream of lizards involved two phases. The first one was characterized by low frequency and high amplitude brain activity. Second — the type of brain activity resembled a revival and was accompanied by rapid eye movements. This dynamics of sleep peculiar to mammals and birds.
Laurent notes that, despite the similarity in the phases of sleep mammals, birds and reptiles diverged greatly in the evolutionary development. The differences between them largely relate and sleep. So, the length of one sleep cycle in lizards is only around 80 seconds. But in humans, this parameter reaches 60-90 minutes. Cats have 30 minutes. In addition, lizards REM and NREM sleep had approximately the same duration, but in humans, REM sleep is usually shorter. In birds the relationship between sleep phases unstable.
“If the division of sleep into stages happened so long ago as we think, the dinosaurs of the Mesozoic era (230-65 million years ago) most likely had similar dynamics of sleep,” said Laurent.
