REM means “rapid eye movement.” This physical feature is considered decisive in determining the onset of the REM sleep phase; however, the term describes several phenomena at once: the state of the brain, the behavioral state, and the state of sleep. In addition to rapid eye movement, it is characterized by muscle paralysis, activity of the cerebral cortex, and other neurological processes. It is in this phase that we are most likely to have lucid dreams.
In 2020, an international team of researchers led by Mark S. Blumberg from the University of Iowa published an article summarizing more than 60 years of research on this phenomenon. REM sleep was discovered by American scientists Eugene Aserinsky and Nathaniel Kleitman in 1953. They were the first to notice a burst of neural activity and rapid eye movement occurring during an adult’s sleep, whereas previously the sleep state was considered entirely passive.
Nowadays, three methods are used to determine REM sleep in the laboratory: an electromyogram (EMG), which shows muscle atony (temporary muscle paralysis), an electrooculogram (EOG), which measures eye movement, and an electroencephalogram (EEG), which records the activity of the cerebral cortex. In a broader sense, for example, when determining REM sleep in some species of mammals or birds, scientists also take into account the main functions of REM sleep – the suspension of thermoregulation and the redistribution of energy for the purpose of physical recovery.
However, over several decades of studying REM sleep, scientists have accumulated more questions than answers. For example, some people do not experience muscle paralysis while sleeping. Birds sleep while standing up, maintaining muscle tone. Other species lack eye movement or other signs. The fetus spends almost the entire day in the REM sleep phase; after birth, we get about 8 hours of REM sleep a day, but in adults, this phase lasts only two hours a night. This is why many sleep researchers believe that children have more lucid dreams. Could it be that our main discoveries concerning REM sleep are still ahead of us?
The article was published in the Current Biology magazine in January 2020.
