The Recuperative Effects of REM Sleep and Stage 4 Sleep on Human Performance After Complete Sleep Loss: Experiment 1

Twelve young (17–21 yrs) male Navy recruits volunteered for a sleep loss study. After 4 baseline days, the Ss were completely deprived of sleep for 2 days and nights. Next followed an experimental phase of 2 days and nights after which all Ss received 2 nights of uninterrupted sleep. During the experimental phase, the 4 Ss in the REM-deprived group were aroused whenever they showed signs of REM sleep. The 4 Ss of the stage 4-deprived group were aroused whenever they showed signs of entering stage 4 sleep, and the 4 Ss of the Control group had uninterrupted sleep. All tests (speed and accuracy of addition, speed and accuracy of self-paced vigilance, errors of omission in experimenter paced vigilance, immediate recall of word lists, and mood) showed significant impairment after the first night of complete sleep loss. But during the experimental (sleep-stage-deprivation) and recovery phases, all three groups showed equal rates of recovery. Depriving the S of stage REM or stage 4 during recovery sleep does not affect the recuperation rate. Frequent arousals (50–100 per night) also do not impair recovery. The amount of sleep is probably more important than the kind of sleep.     

Binocular Depth Perception Following REM Deprivation or Awake State Visual Deprivation

Based upon the demonstration by Wallach and Karsh (1963) that stereoacuity is easily disruptable in the awake state, we postulated that central visual excitation, which is a feature of rapid eye movement sleep, operates to prevent deterioration of depth perception capacity nightly during sleep. Three awake state and four REM sleep conditions, each consisting of an 8-hr period, were tested as follows: Awake: 1) baseline testing, 2) monocular patching, 3) binocular patching; Sleeping: 4) REM sleep deprivation, 5) NREM control (Stage 2 awakenings), 6) eye movement control (Condition 4 with substitution of awake eye movements), 7) uninterrupted sleep. A new device was developed and is described which measures stereoacuity as free as possible from other binocular or monocular cues in an actual depth situation. We replicated Wallach and Karsh's (1963) finding of awake state disruption of stereopsis following monocular patching. However, our results indicate that REM sleep deprivation by awakenings is not detrimental to binocular depth perception the next morning. In a second experiment, we found that binocular depth perception at the end of REM periods is not significantly different from depth perception at the beginning of REM periods. We have concluded that REM sleep does not have the function of enhancement of stereoacuity processing.     

Interaction of REM Deprivation and Stage 4 Deprivation With Total Sleep Loss: Experiment 2

To determine whether prior deprivation of stage REM or stage 4 sleep would potentiate the effects of total sleep loss, 7 young adult males were denied REM sleep and 7 were denied stage 4 sleep for 3 nights before 1 night of total sleep loss. Measures of autonomic and EEG activity, mood, anxiety, Rorschach CET and on several performance tasks were obtained during baseline, following stage deprivation, total sleep loss, and during recovery. There were no marked changes in any area following 3 nights of stage REM and stage 4 deprivation. The changes following total sleep loss were similar for both groups. Prior deprivation of stage REM or stage 4 did not potentiate sleep loss effects. Ss who had no stage deprivation prior to 1 night of sleep loss had more impairment following sleep loss than did the Ss of this study.     

Body Movements During Sleep After Sleep Loss

Following 4 baseline nights, 7 Ss were deprived of REM sleep for 3 nights and 7 were deprived of stage 4 sleep. Both groups were then deprived of total sleep for 1 night and then allowed 2 nights of uninterrupted recovery sleep. Compared to baseline nights, on the first recovery night the number of body movements was significantly reduced in all sleep stages and for total sleep. On the second recovery night, the number of movements was back to baseline level. The increased amount of slow-wave sleep (stages 3 and 4) during recovery sleep was not the primary reason for the reduced body motility.     

INCREASED ACCURACY OF BINOCULAR DEPTH PERCEPTION FOLLOWING REM SLEEP PERIODS

It has been proposed that REM sleep maintains facilitation of coordinated eye movements necessary for accurate binocular depth perception (Berger, 1969). This experiment confirmed the prediction that binocular depth perception would be more accurate at the ends of REM periods than at their onsets. Eight male subjects were studied during 4 non-consecutive nights of sleep. Accuracy of binocular and monocular depth perception were measured with different apparatus in the evening prior to sleep onset, after awakenings made alternately at the onsets or ends of REM periods, and 15 min after awakening in the morning. Accuracy of binocular depth perception was significantly better at the ends of REM periods than at their onsets (p < .001), whereas accuracy of monocular depth perception did not significantly differ. That the monocular task was sensitive to variables of sleep was indicated by impairment at the first REM onset with little variation throughout the night, so that it was significantly worse 15 min after morning awakening than the previous evening (p < .05). In contrast, accuracy of binocular depth perception was significantly better in the morning than the previous evening and at REM onsets (p < .05).     

The Effects of Continuous, High Intensity, White Noise on the Human Sleep Cycle

Eight male college students slept for 8 consecutive nights under conditions of 93 ± 2 dB white noise (N) and under normal quiet conditions (Q). On N nights the percentage of total sleep time spent in stage REM was decreased (p < .001), the percentages of stages 1 and 2 were increased (p < .05, p < .001, respectively) and REM latency was increased (p < .02) compared to Q nights prior to N nights. On Q nights following N nights the percentages of stage REM increased above baseline levels indicating compensatory recovery effects from REM sleep deprivation on the prior N nights. Stages 3 and 4 remained unchanged throughout the study. The reduction in stage REM on N nights was directly attributed to the effects of noise on the CNS and not a secondary result of an increased number of awakenings on N nights.     

EFFECTS OF A STRESSFUL PRESLEEP EXPERIENCE ON ELECTROENCEPHALOGRAPHRECORDED SLEEP

The effects on experimentally uninterrupted sleep of two films, one psychologically stressful and the other neutral, both seen just before bed, were studied in 12 male Ss on 2 nights according to a balanced design. EEG and electro-ocu-logram recordings were made of the first 6 hours of sleep. The stress film significantly increased the number of awakenings associated with rapid eye-movement periods (REMPs), but not that of non-REM sleep awakenings, as well as the proportion of REMPs terminated by spontaneous awakenings. It furthermore increased the frequency of REMs (REM density) during REMPs. These results suggest that the stress film produced a specific REM sleep disturbing effect via anxiety which carried over into the Ss’ sleep and dreams, and that it increased REM density secondary to drive enhancement.     

Facial Muscle Tonus During REM and NREM Sleep

Equipment and procedures were devised for quantifying relatively noise-free recordings of low amplitude chin and lip electromyograms (EMGs) during sleep. A total of 28 REM periods were recorded from 5 young adult female Ss. Tonic EMG levels tended to decline toward their lowest level of the night beginning 5 min in advance of REM periods. With very rare exceptions, the lowest EMG levels of the night were maintained throughout REM sleep. During the 20 min of NREM sleep which followed REM periods, mean EMG levels increased over the REM levels but were lower than those recorded during the 20 min of NREM sleep which preceded the REM periods. This pattern of tonic EMG variation obtained for each of the first 3 REM periods of the night.     

Variability of Sleep Measures in Normal Subjects

Variability of sleep measures during 4 nights was examined in 10 normal young adults. The variables analyzed included: Sleep Stage Percentages; Sleep Time; Latency, Duration, and Cycle Time of REM; No. of REM Periods; and No. of Eye Movements (EM). No indication of First Night Effect was found, except that EM showed significant increases across nights. Although group means corresponded to conventional norms, considerable inter- and intraindividual variability was apparent, with Stage 2 and REM yielding lowest Variability Coefficients. Between nights, consistent positive correlations were found for Awake, REM, REM Latency, and particularly for Stage 4 and EM. Consistency of the relationship between nights for the sleep stages was not generally improved by equating sleep time either within or between Ss. Few intercorrelations between variables were significant. Within nights the first REM Duration was the shortest and the first Non-REM Duration the longest, while neither REM nor Non-REM Cycle Time changed significantly. In 25% of the records, Stage 3 terminated before Stage 4. Variability was discussed in terms of procedural aspects, trait characteristics, and situational factors.     

Biperiden administration during REM sleep deprivation diminished the frequency of REM sleep attempts.

Sixteen subjects were assigned to a group using either placebo or biperiden, with eight subjects in each group. Both groups were studied for one acclimatization night, one baseline night, four nights of rapid eye movement (REM) sleep deprivation and two recovery nights. All the subjects received either placebo or 4 mg biperiden 1 hour before sleep during the four nights of REM sleep deprivation. During the baseline and the recovery nights both groups received placebo capsules. The results showed that REM sleep time during the REM sleep deprivation was reduced by 70-75% below the baseline night in both groups. The number of attempts to enter REM sleep was significantly reduced by biperiden as compared to placebo for each of the four REM sleep deprivation nights. Because the total sleep time in the biperiden group was reduced, the number of REM sleep attempts was corrected by the total sleep time. The adjusted number of REM sleep attempts was also significantly reduced in the biperiden group. REM sleep latency showed a reduction in the placebo group, whereas in the biperiden group REM sleep latency was unchanged throughout the deprivation nights. In the recovery night REM sleep time was increased in both groups, with no differences between the groups. The REM sleep latency showed a reduction in the first recovery night in both groups that persisted through the second recovery night. The above findings support the role of biperiden as a REM sleep suppressive drug.     

Sleepiness and REM Sleep Recurrence: The Effects of Stage 2 and REM Sleep Awakenings

Determinants of daytime sleepiness include sleep length, sleep continuity, and circadian factors. Sleep stage composition has not been seen as influencing subsequent daytime functioning; however, earlier studies did not focus explicitly on sleepiness. The present experiment studied the effects of selective sleep-stage restriction on an objective measure of sleep tendency, and explored the relationship between sleepiness and subsequent REM recurrence during REM deprivation. Daytime sleep latency was measured by a modified Multiple Sleep Latency Test prior to and following two nights of awakenings from either REM or Stage 2 sleep in 16 normal young adults. Sleep latency following these awakenings was also measured. REM sleep and Stage 2 awakenings produced comparable levels of sleepiness, both during the Awakening Nights and subsequent daytime Multiple Sleep Latency Testing. Pooling the groups, daytime and nocturnal sleepiness measures were correlated within individuals. In the REM-Awakening Group, Pre-Awakening daytime sleepiness was associated with the tendency for REM sleep to recur following experimental awakenings. Comparable levels of sleepiness may result from nonspecific processes such as sleep curtailment and fragmentation, or alternatively from separate REM and Stage 2 mechanisms. The relationship between REM sleep and sleepiness is discussed in the context of both state and trait models.     

AN OBSERVATIONAL NOTE ON EYE MOVEMENT PATTERNS DURING REM AND NON REM SLEEP IN SUBJECTS WITH CONGENITAL NYSTAGMUS

Fully developed nystagmus present in five Ss with congenital nystagmus while awake with eyes open or closed did not appear during the REM or non-REM sleep phases. However, rapid conjugate eye movements were present during REM sleep in all five Ss, and could not be distinguished from the patterns recognized in normal subjects.     

Variations in Behavioral Response Threshold Within the REM Period of Human Sleep

Behavioral response threshold measures were compared between REM tonic, REM phasic, as well as NREM-2 sleep. Eighteen young college males were each instructed to respond with one or two microswitch presses upon detection of either of two tones triggered during two non-consecutive nights of sleep in the laboratory. Repeated measures comparisons (ANOVA) of average response threshold values, as determined via a method of limits procedure, showed REM tonic values to be significantly lower than both REM phasic and NREM-2 values while the latter two did not differ significantly from each other. The average of REM period threshold values was significantly lower than NREM-2 values, solely by virtue of the tonic component of the REM period. These differences within the REM period may account in part for greater variance in REM-period behavioral thresholds within and between similar studies. This consideration deserves attention in any attempt to compare the REM period as a whole to NREM-2 stage measures of responsiveness.     

THE DISPLACEMENT OF STAGES 4 AND REM SLEEP WITHIN A FULL NIGHT OF SLEEP

Stage 4 typically occurs dominantly in the first third of a normal night of sleep and REM sleep occurs dominantly in the last third of the night. In this experiment conditions were imposed to prevent these stages from occurring at their usual peak periods. Stage 4 sleep was permitted to occur only during the last two hours of sleep and REM was permitted to occur only during the first two hours of sleep. The results show that each stage can be partially displaced to the peak period of the other, but that stage 4 sleep is elicited more readily late in the sleep period than is REM early during the night.     

Effect of sleep disruption on sleep, performance, and mood

Eleven young adult subjects were briefly awakened after each minute of electroencephalographic-defined sleep for 2 consecutive nights after undisturbed laboratory adaptation and baseline nights. Two undisturbed recovery nights followed disruption nights. On disruption nights, subjects were awakened with an audiometer and signaled the awakening by subjective rating of sleep state or button push response. The disruption procedure resulted in severely fragmented sleep with only very small amounts of slow-wave and REM sleep. Total sleep time was reduced by approximately 1 h on each night. Arousal threshold increased 56 dB across the disruption nights. Following disruption, subjects performed more poorly and rated themselves sleepier than on baseline. The level of decline was similar to that seen after periods of total sleep loss of 40-64 h. Recovery sleep was also similar to that seen after total sleep loss. It was concluded that periodic disruption of sleep, perhaps by destroying sleep continuity, quickly results in impaired function. These data may help explain function loss in severe sleep apneics.     

Renin as a biological marker of the NREM-REM sleep cycle: effect of REM sleep suppression

SUMMARY  We have previously described that, in normal man, the nocturnal oscillations of plasma renin activity (PRA) exactly reflect the rapid eye movement (REM)–non(N)REM sleep cycles, with increasing PRA levels during NREM sleep and decreasing levels during REM sleep. This study was carried out to determine whether REM sleep suppression affects nocturnal renin profiles and to define which sleep stage is essential for renin release.
In a first experimental series, REM sleep was suppressed by using clomipramine, a tricyclic antidepressant. Seven healthy young men were studied once during a night when a placebo was given and once during a night following a single dose of 50 mg clomipramine. Blood was collected every 10 min from 23.00 hours to 07.00 hours. PRA was measured by radio-immunoassay and the nocturnal profiles were analysed using the pulse detection program ULTRA. Clomipramine suppressed REM sleep in all subjects but one, but did not affect the number of SWS episodes nor their duration. Similar PRA profiles were observed in both experimental conditions. Neither the mean levels, nor the number and the amplitude of the oscillations were modified and the normal relationship between slow wave sleep and increasing PRA levels was preserved.
In a second experimental series, REM sleep was prevented by rapidly awakening the subjects as soon as they fell into REM sleep. The four subjects studied attempted several times to go into REM sleep, but only when PRA levels were decreasing. The interruption of REM sleep by short waking periods did not disturb PRA for which the oscillations remained unaffected. Again, the relationship between SWS and increasing PRA levels was preserved.
These results provide evidence that mechanisms increasing slow-wave activity are principally involved in increasing PRA levels and that replacing REM sleep by waking periods and light sleep does not modify nocturnal PRA oscillations.     

Intrinsic dreams are not produced without REM sleep mechanisms: evidence through elicitation of sleep onset REM periods

The hypothesis that there is a strict relationship between dreams and a specific rapid eye movement (REM) sleep mechanism is controversial. Many researchers have recently denied this relationship, yet none of their studies have simultaneously controlled both sleep length and depth prior to non-REM (NREM) and REM sleep awakenings, due to the natural rigid order of the NREM--REM sleep cycle. The failure to control sleep length and depth prior to arousal has confounded interpretations of the REM-dreams relationship. We have hypothesised that different physiological mechanisms underlie dreaming during REM and NREM sleep, based on recent findings concerning the specificity of REM sleep for cognitive function. Using the Sleep Interruption Technique, we elicited sleep onset REM periods (SOREMP) from 13 normal subjects to collect SOREMP and sleep onset NREM (NREMP) dreams without the confounds described above. Regression analyses showed that SOREMP dream occurrences were significantly related to the amount of REM sleep, while NREMP dream occurrences were related to arousals from NREM sleep. Dream properties evaluated using the Dream Property Scale showed qualitative differences between SOREMP and NREMP dream reports. These results support our hypothesis and we have concluded that although 'dreaming' may occur during both REM and NREM periods as previous researchers have suggested, the dreams obtained from these distinct periods differ significantly in their quantitative and qualitative aspects and are likely to be produced by different mechanisms.     

QUANTIFICATION OF THE REM SLEEP CYCLE AS A RHYTHM

The goal of this study was to develop an objective quantitative method for representing the temporal organization of sleep in terms of the period and rhythmicity of REM sleep occurrences. Data on normative human sleep, already scored for stage REM and not stage REM, were subjected to a “binary autocorrelation.” The mean period over 92 nights of sleep for 10 Ss was 101.5 min and quite stable. Data is also presented on variability of the rhythm in terms of an “index of rhythmicity.” Measures of temporal organization may prove to be as significant for sleep research as amount of the various sleep stages.     

"DREAM DETECTOR" AND AUTOMATIZATION OF REMP-AWAKENING TECHNIQUE FOR THE STUDY OF DREAMING

A device named “dream detector” was constructed to automatize the technique of studying dreams during the REM period of sleep (REMP). The principle of the dream detector is to identify the REMP automatically by counting the number of electrooculographically recorded REMs during the period of relative silence in EMG records. When the count number of EMs reaches a preset value, an alarm buzzer is turned on automatically to awaken the S. In preliminary experiments on 5 Ss, 62 out of 70 REMPs (88.6%) in a total of 16 experimental nights were correctly detected by using this device. In only 5 instances (3.5%) was the buzzer turned on during periods other than REMPs. The rate of correct detection was 56% for the first REMP of the night, 93% for the second REMP, and 100% for the following REMPs.     

The REM Cycle in Altered Sleep/Wake Schedules

The length and rhythmicity of the REM cycle was studied using data from three laboratories. In the three studies, 25 subjects obtained their sleep in naps under three different sleep/wake schedules: 60/160 min (N =8), 30/60 min (N =10), and 60/120 min (N =7), over a period of 40 hrs to 10 days. Previous results from these subjects (Moses, Lubin, Johnson, & Naitoh, 1977) indicated that the REM cycle is sleep-dependent, rather than an expression of an ongoing Basic Rest-Activity Cycle (BRAC). As a further test of the sleep-dependent hypothesis, autocorrelation and r² analysis was applied to the compressed sleep (i.e., all wake time between and within sleep periods subtracted) of the baseline, nap, and recovery conditions. Compared to baseline, there were no significant differences in nap REM cycle length in the 60/160 and 60/120 groups; the 30/60 group had significantly shorter cycles. It appeared that this REM cycle shortening was due to the significantly shorter REM episodes in this group. The nap r² values were significantly lower than baseline in the 30/60 and 60/120 groups, indicating increased variability in the timing of REM episodes during naps. All the nap r² values, however, were significantly larger than those obtained from a random distribution of sleep stages. To further examine the effects of the degree of sleep fragmentation on REM cycle rhythmicity, two additional groups of subjects whose sleep was fragmented by either REM or SWS deprivation were compared to the nap groups. REM deprivation was the most disruptive of REM cycle rhythmicity; the r² values for REM deprivation were significantly less than those for napping or SWS deprivation. These data offer further support that the REM cycle is a sleep-dependent rhythm and is not an expression of an ongoing BRAC.