Proof of reptiles’ slow-wave and REM cycle could alter understanding of slumber’s evolution
Stephan Junek/MPI for Brain Research
Lizards might snooze like humans do.
Sleeping lizards appear to share distinctive brain activity patterns with sleeping birds and mammals, researchers report in the April 29 Science. If true, the results suggest that human sleep patterns evolved by around 300 million years ago in a common ancestor of birds, mammals and reptiles.
During sleep, mammal and bird brains alternate between two states of activity. In deep, slow-wave sleep, recordings of the brain’s electrical activity show sparse bursts of big, slow waves. During rapid eye movement, or REM, sleep, brain waves appear small and fast, like those of an awake brain. REM sleep is usually accompanied by quickly twitching eyes.
“The prevailing view has been that REM and slow-wave sleep are limited to mammals and birds,” says study coauthor Gilles Laurent, a neuroscientist at the Max Planck Institute for Brain