REM sleep

Carolyn Fay
2007 Oct 16

Also known as "paradoxical sleep." REM sleep describes a particular phase in the sleep cycle, which is characterized by rapid eye movement, irregular breathing and heartrate, increased blood flow to the genitals, muscle paralysis from the neck down, and increased brain wave activity.  The brain wave pattern of a sleeper in REM sleep looks remarkably similar to that of a waking person, although the subjective experience is more akin to deep sleep, hence the moniker "paradoxical." The discovery of REM sleep electrified the world of sleep science, indicating that humans experience two unique kinds of sleep every night:  REM and NREM (non-REM).  Although REM sleep is associated with dreaming, scientists do not currently agree that REM sleep and dreaming are identical.

Sources:

Dement, The Promise of Sleep

Lavie, The Enchanted World of Sleep

Bulkeley, An Introduction to the Psychology of Dreaming