Scientists from the French National Center for Scientific Research (CNRS) have discovered that lizards, birds and mammals have similar extremely slow physiological rhythms optimized for survival during sleep. The research results were published in the journal Nature Neuroscience (NatNeuro).
We are talking about a global rhythm that covers not only the brain but also the entire body. During sleep, animals synchronously fluctuate in the activity of the nervous system, the work of the heart, blood vessels, breathing rate and muscle tone. In mammals, this rhythm is well known: it is the basis of slow-wave (or deep) sleep.
To trace the origins of this mechanism, researchers studied the sleep of 10 vertebrate species. The sample included seven reptiles, including geckos, bearded dragons and turtles, one bird, one parrot and two mammals for comparison.
The researchers used a multimodal approach, simultaneously recording brain electrical activity, blood flow, respiration and other physiological parameters throughout a complete sleep cycle.
The analysis showed that reptiles and birds continuously experienced slow and steady rhythms during sleep, consistent with the characteristics of slow-wave sleep in mammals. It is expressed in all measuring systems of the body and persists throughout rest.
Evolutionary discoveries were beyond scientists' predictions. The lineages that led to modern mammals, reptiles and birds diverged more than 300 million years ago. However, the core sleep rhythm remained largely unchanged during this time, suggesting its underlying biological significance.
According to the authors, such an ancient mechanism is unlikely to be a side effect of brain function. It can play an important role in restoring the nervous system and reducing sleep-related risks.
