Do lizards dream like us ?

Researchers from the Sleep Team at the Lyon Neuroscience Research Center (CNRS / INSERM / Claude Bernard Lyon 1 University / Université Jean Monnet), together with a colleague from the MECADEV research laboratory (CNRS / Muséum National d'Histoire Naturelle) ¹ have confirmed that lizards exhibit two sleep states, just like humans, other mammals, and birds. They corroborated the conclusions of a 2016 study on the bearded dragon ( Pogona vitticeps ) and conducted the same sleep investigation on another lizard, the Argentine tegu ( Salvator merianae ). Their findings, published in PLOS Biology (October 11, 2018), nevertheless point out differences between species, which raises new questions about the origin of sleep states. During sleep, the body carries out many vital activities: consolidation of knowledge acquired during the day, elimination of metabolic waste from the brain, hormone production, temperature regulation, and replenishment of energy stores. It would appear that this physiological phenomenon is shared by all members of the animal kingdom and has been preserved throughout evolution. But scientists long thought that only land mammals and birds experienced two separate sleep states: slow-wave sleep and REM, or paradoxical, sleep. The latter, associated with dreaming, is a complex phase during which the body exhibits behaviors in limbo between those of sleeping and waking hours.