Active sleep

Active Sleep is a phase of sleep in neonates that appears similar to Rapid Eye Movement (REM) sleep in adults. While it depends on age, neonatal sleep is sometimes scored as Active Sleep, Quiet Sleep, and Wake. This is less specific than the classification of adult's sleep, and is often based on behavioral criteria due to the technical difficulties arising from recording EEG from the neonate.

Scientists are divided on the precise relation between Active Sleep and REM sleep. Some suggest that they are similar, while others say it is an entirely different state, which represents aspects of the developing CNS that are not present in a mature brain, and that certain aspects of REM are not present in Active Sleep due to the immaturity of the CNS in the neonate.