Aserinsky Discovers REM Sleep

Eugene Aserinsky’s discovery of rapid eye movements (REMs) in normal human sleep provided the first objective method of studying neural function and behavioral patterns associated with dreaming.

Summary of Event

As early as 1867, a German psychiatrist named Wilhelm Griesinger Griesinger, Wilhelm speculated on the occurrence of eye movements during dreams. These eye movements, he believed, occurred both during the transition from wakefulness to sleep and during dreaming. From these observations, he concluded that sleep was not a passive but rather an active state. It was another eighty-five years before Eugene Aserinsky (under the guidance of Nathaniel Kleitman) discovered that sleep is not a homogeneous process but is organized in rhythmic cycles of different stages, each of which is characterized by specific behavioral, electrophysiologic, autonomic, and endocrine changes. After studying with a French physiologist, Kleitman had sought to provide a thorough physiological description of sleep. His 1939 book (updated in 1963), entitled Sleep and Wakefulness, Sleep and Wakefulness (Kleitman) constitutes an encyclopedic compendium on the subject; its bibliographic thoroughness has remained unsurpassed. REM sleep
“Regularly Occurring Periods of Eye Motility and Concomitant Phenomena During Sleep” (Aserinsky and Kleitman)[Regularly Occurring Periods of Eye Motility and Concomitant Phenomena During Sleep]
[kw]Aserinsky Discovers REM Sleep (Sept. 4, 1953)
[kw]REM Sleep, Aserinsky Discovers (Sept. 4, 1953)
[kw]Sleep, Aserinsky Discovers REM (Sept. 4, 1953)
REM sleep
“Regularly Occurring Periods of Eye Motility and Concomitant Phenomena During Sleep” (Aserinsky and Kleitman)[Regularly Occurring Periods of Eye Motility and Concomitant Phenomena During Sleep]
[g]North America;Sept. 4, 1953: Aserinsky Discovers REM Sleep[04220]
[g]United States;Sept. 4, 1953: Aserinsky Discovers REM Sleep[04220]
[c]Science and technology;Sept. 4, 1953: Aserinsky Discovers REM Sleep[04220]
[c]Psychology and psychiatry;Sept. 4, 1953: Aserinsky Discovers REM Sleep[04220]
Aserinsky, Eugene
Kleitman, Nathaniel
Dement, William

In 1952, Aserinsky, a graduate student working on his dissertation in the physiology laboratory of Nathaniel Kleitman at the University of Chicago, achieved a breakthrough in modern sleep research. Aserinsky turned his attention to the study of attention in children, using his young son, Armond, as one of his subjects. (According to Aserinsky, the first hint of the presence of REMs came about during the recording of Armond.) While making clinical observations of his young subject’s efforts to attend, he noticed that eye closure was associated with attentional lapse, and thus decided to record these eyelid movements using the electrooculogram Electrooculograms (EOG).

Aserinsky and Kleitman observed that a series of bursts of rapid eye movements occurred about four to six times during the night. The first such REM period took place about an hour after the onset of sleep and lasted from five to ten minutes. Succeeding REM periods occurred at intervals of about ninety minutes each and lasted progressively longer; the final period occupied approximately thirty minutes. (As was later learned, about one fifth of an adult’s typical sleep is REM sleep; however, the percentage is much higher in infants. Animals of many kinds also have REM periods during their sleep.)

Suspecting a correlation of eye movements with dreaming, Aserinsky and Kleitman awakened subjects during REM periods and asked them whether they had been dreaming Dreaming . In a large majority of such awakenings, the subjects acknowledged that they had been dreaming and proceeded to relate their dreams. When a subject was reawakened while his eyes were quiescent, he could rarely remember a dream. Therefore, Aserinsky and Kleitman concluded that rapid eye movements were an objective signal of dreaming. Thus, although investigators still had to rely upon the dreamer’s verbal report to ascertain the content of the dream, the process of dreaming was now opened up to objective study under laboratory conditions.

In order to obtain a more complete representation of the attentional state of his subjects, Aserinsky also recorded brain-wave activity with an electroencephalograph Electroencephalographs (EEG). This combination of measures was fortuitous because, unlike adults, children often enter the REM phase immediately at sleep onset; and these sleep-onset REM periods are especially likely to occur during daytime naps. When Aserinsky’s subjects lost attentional focus and fell asleep, their EEGs showed an activation pattern, and their EOGs showed rapid eye movements. Kleitman quickly deduced that this brain-activated sleep state, with its rapid eye movements, might be associated with dreaming. The two investigators immediately applied the combined EEG and EOG measures to the sleep of adult humans and were able to observe the periodic alternation of REM and non-REM sleep throughout the night. In addition, when the investigators awakened their subjects during REM sleep, these subjects related accounts of dreams.

In 1953, Aserinsky and Kleitman reported their findings (“Regularly Occurring Periods of Eye Motility and Concomitant Phenomena During Sleep”) in the September 4 issue of the journal Science. As is the case with many breakthrough articles, this one was relatively brief (barely two pages). It included the observation that other physiological functions change with the state of the brain mind: Respiratory frequency and heart rate had both been noted as increasing, and their rhythm became irregular.

To describe Aserinsky and Kleitman’s series of experiments (reported in the 1953 article) in more detail, eye movements were recorded by EOGs by employing two sets of leads on each eye, measuring horizontal and vertical changes in corneo-retinal movement. The criterion for identification of eye movement was confirmed by direct observation of several subjects under both weak and gradually intensified illumination. Under the latter condition, video recordings were taken of two subjects without awakening them, thereby further confirming the validity of the investigators’ methods and also the synchronicity of eye movements.

Twenty normal adult subjects were used in several series of experiments. To confirm the conjecture that this particular eye activity was associated with dreaming, ten sleeping individuals in fourteen experiments were awakened and interrogated during the occurrence of this eye movement and also after a period of at least thirty minutes to three hours of nonocular movement. After twenty-seven interrogations during periods of rapid eye movement, twenty responses involved recall of dreams full of detailed visual imagery. Of twenty-three interrogations during ocular inactivity, nineteen subjects disclosed a complete failure of recall.

In another series of experiments, periods of REM were timed during an uninterrupted seven-hour sleep; and in another series, the respiratory and heart rate were calculated during eye movement and compared with a similar period of time during ocular quiescence. Given the fact that these eye movements, EEG pattern (the EEG was used in conjunction with the EOG), and autonomic nervous system activity were significantly related and did not occur randomly, Aserinsky and Kleitman theorized that these physiological phenomena, and presumably dreaming, were very likely all manifestations of a particular level of cortical activity which is encountered normally during sleep. An eye movement period first appeared about three hours after going to sleep, recurred two hours later, and then emerged at somewhat closer intervals a third or fourth time shortly prior to awakening. This investigative method furnished the means of determining the incidence and duration of dream periods.

Aserinsky and Kleitman provided more systematic observations of this phase of ocular motility in sleep in an article entitled “Two Types of Ocular Motility Occurring in Sleep,” “Two Types of Ocular Motility Occurring in Sleep” (Aserinsky and Kleitman)[Two Types of Ocular Motility Occurring in Sleep] published in the Journal of Applied Physiology in 1955. This classic paper first described in detail the link between dreaming and rapid eye movements, only briefly mentioned in their earlier article.

William Dement, a physiologist and subsequent collaborator of Kleitman’s, later confirmed Aserinsky and Kleitman’s hypothesis. Also, following Aserinsky and Kleitman’s groundbreaking article on human REM sleep in 1953, and their immediate recognition of REM as the physiological basis of dreaming, Dement established that an identical phase of sleep occurs in cats; he published his results in the 1958 EEG Journal.


Aserinsky’s discovery stimulated extensive research on the physiological aspects of REM sleep. Among the earliest discoveries was that of a characteristic brain-wave pattern accompanying REM sleep. This pattern is distinguished by rapid, low-voltage waves, not unlike those that occur in the waking state but very different from the slower, high-voltage waves of non-REM sleep. During REM sleep, breathing and pulse rates are more irregular than during non-REM sleep, suggesting emotional disturbance; there is a relaxation of the head and neck muscles; and, in men, the penis becomes partially or fully erect.

Studies of the relationship of the subject matter of dreams to physiological changes during REM periods have not sufficiently established any close correlations. Although early investigations indicated that the pattern of eye movements is correlated with the directions in which the dreamer is looking in the dream, subsequent evidence raises serious doubt concerning this hypothesis. More conclusive evidence exists demonstrating the theory that dreaming can sometimes occur during non-REM periods. This possibility suggests that dreaming may be more or less continuous during sleep, but that conditions for the recall of dreams are more favorable following REM awakenings than otherwise. In any case, the prevailing view is that REMs are not an objective sign of all dreaming, but that they indicate reliably when a dream is most likely to be recalled.

Aserinsky’s discovery of a stage of sleep during which most dreaming seems to occur led to experiments to investigate what would happen if a sleeping person were deprived of REM sleep. These studies concluded that there is an overwhelming demand for REM sleep. Because REM sleep usually accompanies dreaming, it was also concluded from these studies that there is a strong need to dream. Later studies with prolonged deprivation of REM sleep, however, did not confirm the degree of behavioral changes noted earlier. Thus, it can be concluded that there is definitely a need for REM sleep, but the question of whether there is also a need to dream is still open to debate.

By using an EEG to monitor sleep during the night and by awakening subjects during REM periods, it has been conclusively established that everyone normally dreams every night. Even persons who have never remembered a dream in their lives will do so if awakened during a REM period. New methods of collecting dreams have given rise to new methods of analyzing them. The principal method employed in analyzing reported dreams, whether collected in the laboratory or at home, is content analysis. This method consists of classifying the various elements that appear in dreams (for example, males and females, familiar persons and strangers, and objects).

The understanding of dreams has been greatly advanced in the twentieth century not only by analytic work but also by Aserinsky’s discovery of REM sleep. The discovery that REM sleep is regularly recurrent, and that dreaming is its concomitant state of consciousness, opened the doors to a truly objective investigative approach to the mind-brain question. The recognition of REM sleep as a predictable phase of brain activity in the sleep of all mammals further provided animal models for in-depth exploration of the physical basis of dreaming. Consequently, explicit theories of how REM sleep is generated became possible; also, many puzzling features of the dream state could be accounted for in physiological terms. REM sleep
“Regularly Occurring Periods of Eye Motility and Concomitant Phenomena During Sleep” (Aserinsky and Kleitman)[Regularly Occurring Periods of Eye Motility and Concomitant Phenomena During Sleep]

Further Reading

  • Cohen, David B. Sleeping and Dreaming. New York: Pergamon Press, 1979. Although this thorough investigation of the origins, nature, and functions of sleeping and dreaming discusses the advances in sleep research since Aserinsky and Kleitman, Cohen discusses the work of these two scientists in its historical context. First half of book is devoted to REM sleep. Contains references, name and subject index.
  • Gottesmann, Claude. The Golden Age of Rapid Eye Movement Sleep Discoveries, 1965-1966. Hauppauge, N.Y.: Nova Science, 2005. Detailed, focused study of two of the most productive years for the science of sleep and dreaming, during which Aserinsky’s discovery bore its greatest fruit. Bibliographic references and index.
  • Hobson, J. Allan. The Dreaming Brain. New York: Basic Books, 1988. This eminently readable work, written for layperson and expert alike, discusses the brain-based approach to dreaming. It covers dream research from the nineteenth century to 1988. In a chapter on the discovery of REM sleep and dreaming, Hobson discusses the work of Aserinsky and Kleitman. Contains excellent bibliography.
  • Horne, James. Why We Sleep. New York: Oxford University Press, 1988. In this work, geared toward the layperson as well as the expert, the author discusses the functions of sleep in humans and other mammals. In the chapter on REM sleep, the work of Aserinsky and Kleitman is briefly mentioned.
  • Kleitman, Nathaniel. Sleep and Wakefulness. Rev. ed. Chicago: University of Chicago Press, 1963. Referred to as the “old testament of sleep research,” this classic work is a scholarly and encyclopedic summary of all of the relevant research in sleep from 1939 to 1963. Contains voluminous bibliography, with more than four thousand entries.
  • Oswald, Ian. Sleeping and Waking. New York: Elsevier, 1962. This brief and somewhat technical work is devoted to the psychology and physiology of sleep and waking. It offers an account of the advances in sleep research since Kleitman’s Sleep and Wakefulness and briefly alludes to Aserinsky’s work in the section dealing with REM sleep.

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