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  • 1. Journal of Experimental Psychology Vol. S3, No. 5, 1957 THE RELATION OF EYE MOVEMENTS DURING SLEEP TO DREAM ACTIVITY: AN OBJECTIVE METHOD FOR THE STUDY OF DREAMING WILLIAM DEMENT i AND NATHANIEL KLEITMAN 2 Department of Physiology, University of Chicago The study of dream activity and possibility of unintentional cuing by its relation to physiological variables E. (b) The subjective estimate of during sleep necessitates a reliable the duration of dreams was compared method of determining with precision with the length of eye movement when dreaming occurs. This knowl- periods before awakening, reasoning edge, in the final analysis, always that there should be a positive cor- depends upon the subjective report relation if dreaming and eye move- ments were concurrent, (c) The pat- of the dreamer, but becomes relatively objective if such reports can be sig- tern of the eye movements was related nificantly related to some physio- to the dream content to test whether logical phenomena which in turn can they represented a specific expression be measured by physical techniques. of the visual experience of dreaming Such a relationship was reported or merely a random motor discharge by Aserinsky and Kleitman (1) who of a more active central nervous observed periods of rapid, conjugate system. eye movements during sleep and METHOD found a high incidence of dream recall The Ss for the experiments were seven adult in Ss awakened during these periods males and two adult females. Five were studied and a low incidence when awakened intensively while the data gathered from the at other times. The occurrence of other four were minimal with the main intent of confirming the results on the first five. these characteristic eye movements In a typical experiment, S reported to the and their relation to dreaming were laboratory a little before his usual bedtime. He confirmed in both normal Ss and was instructed to eat normally but to abstain schizophrenics (4), and they were from alcoholic or caffeine-containing beverages shown to appear at regular intervals on the day of the experiment. Two or more electrodes were attached near the eyes for in relation to a cyclic change in the registering changes in the corneoretinal potential depth of sleep during the night as fields as the eyes moved. Two or three elec- measured by the EEC (5). trodes were affixed to the scalp for recording This paper represents the results brain waves as a criterion of depth of sleep. The S then went to bed in a quiet, dark room. of a rigorous testing of the relation All electrode lead wires were further attached to between eye movements and dream- the top of the head and from there to the lead ing. Three approaches were used: box at the head of the bed in a single cord to (a) Dream recall during rapid eye minimize the possibility of entanglement and movement or quiescent periods was allow S a free range of movement. The po- tentials were amplified by a Model III Grass elicited without direct contact be- Electroencephalograph in an adjoining room. tween E and S, thus eliminating the The electroencephalograph was run continuously 1 throughout the sleep period at a paper speed of Postdoctoral Public Health Service Research 3 or 6 mm. per sec. which allowed easy recog- Fellow of the National Institute of Neurological nition of eye-movement potentials. A faster Diseases and Blindness. 2 speed (3 cm./sec.) was used for detailed ex- Aided by a grant from the Wallace C. and amination of the brain waves although the Clara A. Abbott Memorial Fund of the Uni- slower speed permitted at least an approximate versity of Chicago. 339
  • 2. 340 WILLIAM DEMENT AND NATHANIEL KLEITMAN TABLE 1 through a stage similar to that ac- companying the rapid eye movement SUMMARY OF EXPERIMENTS periods occurring later in the night. These findings concerning associated Average Average Awak- Nights 5s enings Awakenings Sleeping Nightly Slept EEG patterns were identical with Time previous observations on uninter- DN 6 7:50 50 8.3 rupted sleep (5). 12 IR 4:20 65 5.4 KC 17 6:00 An accurate appraisal of the mean 74 4.4 WD 11 77 7.0 6:30 duration of the REM periods was 55 PM 9 6.1 6:20 impossible since most were terminated KK 10 2 5.0 6:00 1 6 6.0 SM 6:40 artificially by an awakening. How- DM 1 4 4.0 7:00 ever, those that were not so termi- 2 10 5.0 6:10 MG nated varied between 3 and SO min. 61 351 S.7 6:00 Totals in duration with a mean of about 20 min., and they tended to be longer estimation of the gross pattern. The criteria of the later in the night they occurred. eye-movement potentials and their differentia- The eyes were not constantly in tion from brain wave artifacts have been dis- motion during such periods; rather, cussed at length elsewhere (1,4). the activity occurred in bursts of one At various times during the night Ss were or two, up to fifty or a hundred awakened to test their dream recall. The return to sleep after such an awakening invariably took movements. A single movement was less than 5 min. Table 1 is a summary of the generally accomplished in .1-.2 sec. experiments showing the number of nights each and was followed by a fixational pause S slept and the number of awakenings. In all, of varying duration. The amount, 21% of the awakenings fell in the first 2 hr. of sleep, 29% in the second two, 28% in the third pattern, and size of the movements varied irregularly from period to two, and 22% in the fourth two. period. RESULTS The REM periods occurred at fairly regular intervals throughout the The occurrence of rapid eye move- during night. The frequency of occurrence ments?—Discrete periods seemed to be relatively constant and which their eyes exhibited rapid movements were observed in all nine characteristic for the individual. DM Ss every night they slept. These and WD averaged one eye-movement periods were characterized by a low- period every 70 min. and every 75 voltage, relatively fast pattern in the min. respectively. KC averaged one EEG. The interspersed periods in eye-movement period every 104 min. which rapid eye movements were The other Ss fell between these two absent showed EEG patterns in- extremes. The average for the whole dicative of deeper sleep, either a group was one REM period every 92 predominance of high-voltage, slow min. Despite the considerable disturb- activity, or frequent, well-defined ance of being awakened a number of sleep spindles with a low-voltage background. No REM's were ever times, the frequency and regularity observed during the initial onset of with which REM periods occurred sleep although the EEG always passed was almost exactly comparable to that seen previously in a study of 3 In most of the remaining text the following uninterrupted sleep (5). If the awak- abbreviations will be used: REM's (rapid eye movements) and NREM's (no rapid eye move- ening occurred during a NREM period, the return to sleep was never ments).
  • 3. 341 EYE MOVEMENTS DURING SLEEP TABLE 2 associated with REM's, nor was the time of onset of the next REM period INSTANCES OF DREAM RECALL AFTER AWAK- ENINGS DURING PERIODS OF RAPID EYE markedly changed from that which MOVEMENTS OR PERIODS OF No would have been expected in the RAPID EYE MOVEMENTS absence of an awakening. An awak- ening during an REM period gen- Rapid Eye No Rapid Eye erally terminated the REM's until Movements Movements 5 the next period, and the sequence of Dream No Dream No EEC changes, excluding the brief Recall Recall Recall Recall period of wakefulness, was the same DN 3 17 9 21 as that following an REM period IR 26 8 2 29 that ended spontaneously. Excep- KG 4 3 31 36 WD 5 34 37 tions occurred when S was awakened 1 PM 6 23 24 2 during an REM period in the final KK 1 4 0 5 hours of sleep when the period was 2 2 SM 2 0 2 1 1 DM 0 likely to be quite long if uninter- 4 3 0 3 MG rupted. On these occasions, the 11 REM's sometimes started up again 152 39 149 Totals when S fell asleep. It seemed as though a period of heightened CNS mentary impressions of content, were activity had not run its normal course considered negative. and, although S was able to fall The awakenings were done either asleep, he continued to dream. Eye movement periods and dream during REM periods or at varying increments of time after the cessation recall.—For all awakenings to elicit of eye movements during the inter- dream recall, the arousing stimulus was the ringing of an ordinary door- spersed periods of NREM's. The Ss, bell placed near the bed and suffi- of course, were never informed when awakened whether or not their eyes ciently loud to ensure immediate had been moving. awakening in all levels of sleep. The Table 2 shows the results of the Ss then spoke into a recording device near the bed. They were instructed attempts to recall dreams after the to first state whether or not they had various awakenings. The REM or been dreaming and then, if they could, NREM awakenings for PM and KC to relate the content of the dream. were chosen according to a table of When S had finished speaking E, random numbers to eliminate any possibility of an unintentional pat- who could hear their voices, occasion- ally entered the room to further tern. For DN, a pattern was fol- question them on some particular lowed: first three REM awakenings, then three NREM awakenings, and point of the dream. There was no communication between S and E in so on. WD was told he would be any instance, it must be emphasized, awakened only when the recording indicated that he was dreaming, but until S had definitely commited him- self. The Ss were considered to have REM and NREM awakenings were been dreaming only if they could then interspersed randomly The relate a coherent, fairly detailed type of awakenings for IR was chosen according to the whim of E description of dream content. As- sertions that they had dreamed with- The Ss uniformly showed a high incidence of dream recall following out recall of content, or vague, frag-
  • 4. 342 WILLIAM DEMENT AND NATHANIEL KLEITMAN REM awakenings and a very low In general, Ss were best able to make an emphatic statement that incidence of recall following awak- enings during periods of NREM's they had not been dreaming when the regardless of how the awakenings NREM awakenings were done during an intermediate stage of sleep as were chosen. In particular, DN was indicated by a brain-wave pattern of not more accurate than the others spindling with a low-voltage back- although there was a pattern he might have learned, and WD was not ground. When aroused during a less accurate although he was de- deep stage of sleep characterized by liberately misled to expect to have high-voltage, slow waves in the EEG, Ss often awoke somewhat bewildered. been dreaming every time he was awakened. Over a narrow range, In this state they frequently felt that some Ss appeared better able to recall they must have been dreaming al- dreams than others. though they could not remember the Table 3 compares the results of the dream or, on the other hand, that first half of the series of REM awak- they had not been asleep at all. They enings with the last half. Practice sometimes had a great variety of was certainly not a significant factor feelings to describe—such as pleasant- as only one S showed any degree of ness, anxiety, detachment, etc., but improvement of recall on later nights these could not be related to any as compared with the early ones. specific dream content. The incidence of dream recall Most of the instances of inability dropped precipitously almost imme- to recall dreaming after awakenings diately upon cessation of REM's. In during REM periods occurred in the 17 NREM awakenings that were done early part of the night. Of 39 nega- within 8 min. after the end of a REM tive reports in the entire study, 19 occurred after awakenings during period, 5 dreams were recalled. Al- though small, this was a much higher REM periods falling in the first 2 hr. incidence of dream recall than oc- of sleep, 11 after REM awakenings curred when the NREM awakenings during the second 2 hr., S in the third followed the end of REM periods 2 hr., and 4 in the last 2 hr. There by more than 8 min. In the latter was no such variation relating to category only 6 dreams were recalled awakenings during the interspersed in 132 awakenings. periods of ocular quiescence, the incidence of dream recall being uni- TABLE 3 formly low, regardless of whether the COMPARISON OF FIRST HALF OF SERIES OF RAPID early or late part of the night was EVE MOVEMENT AWAKENINGS WITH being considered. SECOND HALF Length' of rapid eye movement periods and subjective dream-duration esti- First Half Second Half mates.—If the length of the REM 5 periods were proportional to the No Dream No Dream Recall Recall Recall Recall subjectively estimated duration of the dreams, it would further help to 12 5 DN 1 8 12 14 S IR 3 establish the relatedness of the two 18 2 18 KC 2 and would give some information 19 2 18 WD 3 12 3 12 PM about the rate at which dreaming 3 progresses. 73 13 67 Total 19 At first, Ss were awakened at
  • 5. 343 EYE MOVEMENTS DURING SLEEP TABLE 4 ever, the lengths of the dream narra- tives still showed a significant relation- RESULTS OF DREAM-DURATION ESTIMATES AFTER S OR 15 MIN. OF RAPID ship to the duration of REM periods EYE MOVEMENTS before awakening. Table S shows the correlations between minutes of 5 Minutes 15 Minutes REM's and lengths of dream nar- 5 ratives for each S. The number of Wrong Right Wrong Right words in the narrative was the meas- DN urement of length. Of the 152 S 2 8 S IR 3 11 1 7 dreams recalled, 26 were not included KC 7 1 12 0 because poor recording did not allow WD 13 1 IS 1 PM 6 2 3 8 complete transcription. Dream nar- ratives recalled after 30 or as much as 4S Total 6 13 47 SO min. of REM's were not a great deal longer than those after IS min. although Ss had the impression that various increments of time after the they had been dreaming for an un- REM's had begun and were requested usually long time. This was perhaps to estimate to the nearest minute the due to inability to remember all the amount of time they had been dream- details of very long dreams. ing. This proved to be too difficult, Specific eye-movement patterns and although the estimates were always visual imagery of the dream.—The of the same order of magnitude as the quality and quantity of the REM's lengths of the REM periods, and were themselves showed endless variation. occasionally exactly right. There was much or little movement, A series was then done in which Ss big or small movements, and so on. were awakened either S or IS min. As has been stated, the movements after the onset of REM's and were occurred in bursts of activity sepa- required on the basis of their recall rated by periods of relative inactivity. of the dream to decide which was the However, the brain-wave stage during correct duration. The 5- or IS-min. the whole period remained the same periods were chosen on the basis of a whether there was much or little random series. Table 4 shows the movement at any given moment of results of these awakenings. All Ss the period. were able to choose the correct dream It was hypothesized that the move- duration with high accuracy except ments represented the visual imagery DN. This S, however, made most of the dream, that is, that they of his incorrect choices by estimating IS min. to be 5 min. This is con- TABLE 5 sistent with the interpretation that CORRELATION BETWEEN DURATION OF REM the dream was longer, but he was only PERIODS IN MINUTES AND NUMBER OF able to recall the latter fraction and WORDS IN DREAM NARRATIVES thus thought it was shorter than it actually was. Number P r Subjects In addition to depending on the of Dreams amount of actual dreaming, the <.02 .60 DN IS lengths of the dream narratives were <.001 .68 IR 25 .40 <.05 31 KC undoubtedly influenced by many .71 <.001 3S WD other factors as, for example, the <.02 .53 PM 20 loquacity or taciturnity of S. How-
  • 6. 344 WILLIAM DEMENT AND NATHANIEL KLEITMAN corresponded to where and at what eye movement In these, the dreams the dreamer was looking. An at- all had the common property that tempt to account for every movement the dreamer was watching something by having S state chronologically in at a distance or just staring fixedly at what directions he had gazed in the some object In two of these awak- dream proved futile. The Ss could enings in different Ss the patterns not recall the dream with such a high were the same, as follows: about a order of detail and precision. minute of ocular inactivity followed In a slightly different approach, Ss by several large movements to the were awakened as soon as one of four left just a second or two before the predominant patterns of movement awakening. Both instances, inter- estingly enough, were virtually identi- had persisted for at least 1 min. and were asked to describe in detail the cal as regards dream content. In one case S was driving a car and dream content just before awakening. The four patterns were: (a) mainly staring at the road ahead. He ap- vertical eye movements, (b) mainly proached an intersection and was horizontal movements, (f) both ver- startled by the sudden appearance of tical and horizontal movements, and a car speeding at him from the left (d) very little or no movement. The as the bell rang. In the other, the dreamer was also driving a car and prevalence of the horizontal or vertical components was determined by plac- staring at the road ahead. Just ing leads both vertically and hori- before the awakening he saw a man standing on the left side of the road zontally around the eyes. A total of 35 awakenings was and hailed him as he drove past. accumulated from the nine Ss. In the 21 awakenings after a mix- ture of movements Ss were always Periods of either pure vertical or looking at things close to them, horizontal movements were extremely rare. Three such periods of vertical objects or people. Typical reports movements were seen. After each were of talking to a group of people, looking for something, fighting with of these the dream content involved someone, and so forth. There was a predominance of action in the no recall of distant or vertical vertical plane One S dreamed of activity. standing at the bottom of a tall cliff operating some sort of hoist and In order to confirm the meaning- fulness of these relationships, 20 looking up at climbers at various levels and down at the hoist ma- naive Ss as well as 5 of the experi- chinery. Another S dreamed of mental Ss were asked to observe distant and close-up activity while climbing up a series of ladders looking awake. Horizontal and vertical elec- up and down as he climbed. In the trodes were attached. The eye-move- third instance the dreamer was throw- ing basketballs at a net, first shooting ment potentials in all cases were and looking up at the net, and then comparable in both amplitude and pattern to those occurring during looking down to pick another ball off the floor. Only one instance of pure dreaming. Furthermore, there was horizontal movement was seen. In virtually no movement, as indicated the associated dream S was watching by the eye potentials, when viewing two people throwing tomatoes at each distant activity, and much movement other. On 10 occasions Ss were while viewing close-up activity. Ver- tical eye-movement potentials were awakened after 1 min. of little or no
  • 7. EYE MOVEMENTS DURING SLEEP 345 and only 3 out of the 25 £s studied ex- always at a minimum except for the hibited foot twitches. upward movements accompanying Incidental observations have been blinking, and in a few cases when E made on the occurrence of dreaming tossed a ball in the air for them to by investigators studying brain waves watch. during sleep (2, 3, 6, 7, 8).
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