How was REM sleep discovered?

In a previous post we broke down the different stages of sleep. One of the most interesting stages of sleep is REM (Rapid Eye Movement) sleep. This is the stage of sleep where we dream. In this post I am going to answer a question that one of my patients asked me – how was REM sleep discovered?

Dr. Nathanial Kleitman

REM sleep was discovered by Drs. Nathanial Kleitman and Eugene Aserinsky. Dr Kleitman was a Professor in physiology. In 1925 he joined the University of Chicago and set up the world’s first sleep laboratory, which he designed and built with the help of his students. In 1939 he wrote a pioneering book, Sleep and Wakefulness, and a revised version of this was published in 1963. Dr Eugene Aserinsky was a student of Dr Kleitman.

In September 1953 Dr Kleitman and Dr Aserinsky published their research in which they discovered REM sleep. Before 1953, slow rolling or pendular eye movements had been observed in both sleeping children and adults by a number of researchers going as far back as 1922. Similar observations were also made in 1941 in patients who had been anaesthetised.

The discovery by Dr Kleitman and Dr Aserinsky was different. They observed eye movements that were “rapid, jerky and binocularly symmetrical”. In addition, they noted that these eye movements occurred in cycles across the night. The electroencephalographic (EEG) changes during REM sleep were associated with low amplitude, irregular frequency activity, which was said to be similar to what is observed during wakefulness.

In Dr Kleitman and Dr Aserinsky recruited 20 subjects and carried out a series of several experiments. Some subjects were involved in more than one experiment. These subjects slept under observation in the sleep laboratory, and were woken during periods of sleep where the jerky eye movements (referred to as ocular motility) took place. Their research paper states, “of 27 interrogations during ocular motility, 20 revealed detailed dreams usually involving visual imagery”. In relation to the remaining 7 subjects, it was reported they had “a complete failure of recall, or else, the feeling of having dreamed, but with inability to recollect any detail of the dream”.

Dr Eugene Aserinsky

Dr Kleitman and Dr Aserinsky also woke subjects during periods of sleep where there were no observed eye movements, referred to as ocular inactivity. Their research paper states, “of 23 interrogations during ocular inactivity, 19 disclosed complete failure of (dream) recall”.

Further observations in the sleeping subjects during these periods of rapid eye movements included changes in respiratory and heart rate. Dr Kleitman and Dr Aserinsky concluded “The fact that these eye movements, EEG pattern, and autonomic nervous system activity are significantly related and do not occur randomly suggests that these physiological phenomena, and probably dreaming, are very likely all manifestations of a particular level of cortical activity which is encountered normally during sleep.”

Dr Kleitman and Dr Aserinsky also commented that eye-movement periods first appear around 3 hours after going to sleep, reoccur 2 hours later, and then occur again at close intervals a third or fourth time shortly before wakening.

This pioneering research demonstrated that there were 2 major types of sleep, REM sleep and Non-REM sleep. Dr Kleitman and Dr Aserinsky also showed that sleep included active brain processes.

Dr Kleitman is recognised as the father of modern sleep research. He died in Los Angeles, California on August 13, 1999 at the age of 104. Dr Aserinsky died on July 22 1998 when his car hit a tree north of San Diego. He was 77.


Aserinsky E, Kleitman N: Regularly occurring periods of eye motility, and concomitant phenomena, curing sleep. Science 118:273–274, 1953

Aserinsky E. The discovery of REM sleep. J Hist Neurosci. 1996 Dec;5(3):213-27. doi: 10.1080/09647049609525671. PMID: 11618742.

Neylan TC. Fiftieth anniversary of the discovery of rapid eye movement (REM) sleep. J Neuropsychiatry Clin Neurosci. 2003 Fall;15(4):453. doi: 10.1176/jnp.15.4.453. PMID: 14627773



The articles in the Sleep Psychiatrist blog have been written by Dr Dipesh Mistry. They are for educational and informational purposes only, and should not be regarded as medical advice. Always seek advice from your sleep physician, personal physician, psychiatrist, or any other suitably qualified healthcare professional in relation to any interventions or treatment for your sleep, mental health or physical health.

Share the Post: