The Effects of Presleep Stimuli of Different Sources and Types on REM Sleep

The sleep patterns of 12 experienced meditators and 9 age-matched prospective meditators were compared to determine the effect of presleep stimuli of different sources and types on rapid eye movement (REM) sleep. All subjects were EEG monitored for two nights. On both nights the experienced meditators attended to internal stimuli, i.e. meditated prior to sleep, and the prospective meditators attended to external stimuli, i.e. listened to music through earphones, for an equal time. The music group had a significantly higher REM percent. Post hoc tests showed this was not due to a rebound following a difficult adaptation night. To test whether the elevation following music was a response specific to those committed to presleep external stimulus reduction, a second study compared the REM percent of a non-meditation oriented student sample following presleep verbal or music stimulation to their base rate. These subjects showed REM percents higher than their base after music and lower than base following verbal stimulation.     

Shortened REM Latency: Consequence of Psychological Strain?

Previous research has demonstrated that in healthy subjects sit uat ional strain may provoke not only sleep disturbances characteristic of depression (e.g., shortened REM latencies), but also alterations in dream content. Nevertheless, there are some controversial results. The aim or our study was to clarify these inconsistencies by developing a design which might avoid some methodological problems which were present in some of these previous studies. Eleven male subjects slept in the laboratory for 7 consecutive nights. During 1 evenings they saw a stressful and a neutral movie in randomized order. The subsequent nights included REM sleep awakenings for the purpose of dream collections. Whereas the subjects were demonstrably affected by the disturbing films, the patterns of subsequent sleep remained unchanged. In contrast manifest content of the initial dreams were clearly altered. Whereas the modes of dreaming were quite different within post-stress nights, mood was unproved the next morning in all subjects. The results are discussed within the framework of several prevailing concepts about sleep, dreams, and psychological strain.     

Memory sources of REM and NREM dreams

Sixteen male volunteers slept 4 nonconsecutive nights each in a sleep laboratory. They were awakened for one dream report per night. Awakenings were made, in counterbalanced order, from early-night and late-night rapid-eye movement (REM) and non-REM (NREM) sleep. Following dream reporting, subjects were asked to identify memory sources of their dream imagery. Two independent judges reliably rated mentation reports for temporal units and categorized memory sources as autobiographical episodes, abstract self-references, or semantic knowledge. We replicated earlier findings that semantic knowledge is more frequently mentioned as a dream source for REM than for NREM reports. However, with controls for length of reports, the REM-NREM difference disappeared, indicating that the stage difference in memory sources was not independent of stage difference in report lengths. There was a significant effect of time of night on source class, but only in REM sleep: Both without and with controls for report length, more semantic sources were cited for late than for early REM dreams.     

Changes in dreaming induced by CPAP in severe obstructive sleep apnea syndrome patients

To study dream content in patients with severe obstructive sleep apnea syndrome (OSAS) and its modification with Continuous Positive Airway Pressure (CPAP) therapy. We assessed twenty consecutive patients with severe OSAS and 17 healthy controls. Polysomnograms were recorded at baseline in patients and controls and during the CPAP titration night, 3 months after effective treatment and 2 years later in patients. Subjects were awakened 5-10 min after the beginning of the first and last rapid eye movement (REM) sleep periods and we measured percentage of dream recall, emotional content of the dream, word count, thematic units, sleep architecture and REM density. Dream recall in REM sleep was similar in patients at baseline and controls (51.5% versus 44.4% respectively; P = .421), decreased to 20% and 24.3% the first and third month CPAP nights, and increased to 39% 2 years later (P = 0.004). Violent/highly anxious dreams were only seen in patients at baseline. Word count was higher in patients than in controls. REM density was highest the first CPAP night. Severe OSAS patients recall dreams in REM sleep as often as controls, but their dreams have an increased emotional tone and are longer. Despite an increase in REM density, dream recall decreased the first months of CPAP and recovered 2 years later. Violent/highly anxious dreams disappeared with treatment. A dream recall decrease with CPAP is associated with normalization of sleep in OSAS patients.     

Vertical inversion of the visual field and REM sleep mentation

The effects of the vertical inversion of the visual field on REM sleep mental activity were examined to explore the potential involvement of this activity in information processing. In a first experiment, four male subjects slept in the laboratory for two sessions of 6 consecutive nights: 2 adaptation nights, 2 nights of polysomnography and 2 nights of dream collection. During the days preceding Nights 3, 4, 5, 6 of each session, the subjects wore glasses which, during the second session, completely inverted (rotation of 180°) their visual field. In a second experiment with four other male subjects, the order of conditions was reversed and the experimental condition (visual inversion) was introduced twice. The data of the two experiments were combined. Overall, following visual inversion, there were significant increases in the proportion of dreams containing motor and visual difficulties ( P <0.005), misfortunes ( P <0.05) and dreamer confusion ( P <0.05) and a decrease in dreamer participation ( P <0.05). Only 4 of the 8 subjects experienced incorporations of the inverted visual field into their dreams and they tended to perform better on two of three tests of adaptation to the visual inversion. The observed changes in dreams are consistent with the notion of continuity between waking and dreaming since they appear to reflect the waking preoccupation and psychological state associated with visual inversion.     

Locating NREM Dreaming Through Instrumental Responses

One difficulty associated with the study of dreams has been the absence of an objective indicator of dreaming in sleep other than REM. This study explores the use of a subjective judgment and instrumental response to mark the occurrence of dreams. Content reports of 8 subjects collected under two conditions were compared. On 2 nights the experimenter determined the time of the awakening and on the other 2 the subject's behavioral response was used as the indicator. The subjects' judgments that they were dreaming proved to be more accurate than was the experimenter's. A single case study of a high NREM responder carried out for 9 nights showed the frequency of NREM dreaming signals to covary with presleep mood.     

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.     

Effects of dream reflection on waking affect: awareness of feelings, rorschach movement, and facial EMG

The clinical and research literature suggests that waking dream reflection increases awareness of feelings. To examine this possibility, 16 male and 16 female participants spent a single night in the sleep laboratory while rapid eye movement (REM) sleep physiology and facial electromyogram (EMG) were monitored. Participants in the dream imagery condition were awakened from REM sleep and asked to reflect on their dreams. Participants in the fantasy imagery condition were awakened from REM sleep and asked to reflect on guided fantasies modeled on dream narratives. Participants were asked to reflect either on the affective connotations of their imagery or on the cognitive aspects of their imagery. Unexpectedly, self-reported awareness of feelings was less common during either affective or cognitive reflection on dreams than during such reflection on fantasies, especially for females. Also, kinesthetic sensitivity, as indicated by Rorschach movement responses, was less after dream reflection than after reflection on fantasy imagery, again especially for females. In contrast, facial EMG activity was greater during dream reflection than during fantasy reflection. Since facial EMG during REM sleep and during dream reflection was correlated with self-reported orienting within dream imagery, these results are understandable as evidence for the "carry-over" of REM orienting activity during dream reflection, resulting in reduced affective/kinesthetic sensitivity and reduced awareness of feelings.     

The Effect of Presleep Focal Attention Load on Subsequent Sleep Patterns

The hypothesis that a load on focal attention prior to sleep results in subsequent changes in sleep patterns was investigated. Eight females and 2 males slept in the laboratory for 4 nights: 2 adaptation nights, 1 experimental night preceded by a focal attention load, and 1 control night preceded by relaxed activity. On the experimental night, time in bed, total sleep time, and stage REM sleep were significantly longer than on the control night. The results support the hypothesis and suggest that attention during REM sleep has a unique character.     

REM Sleep Interruption: Experimental Shortening of REM Period Duration

This experiment concerns itself with the extent to which psychological factors can influence normal sleep patterns. After 4 baseline nights of uninterrupted sleep, each of 4 Ss was awakened in the course of 2 nights during every REM period about 10 min following each REM onset. Ss, however, were not REM deprived. The interruption nights were followed by a recovery night of uninterrupted sleep. All nights were consecutive. The results show that during recovery nights all Ss continued to have significantly shorter than normal REM periods by going into NREM sleep at about the time they would have been awakened during the interruption nights. These shortened REM periods occurred even during early morning hours, when REM periods normally become longer. Arguments are advanced that this finding may best be explained in terms of a conditioned avoidance response.     

Overnight emotional adaptation to negative stimuli is altered by REM sleep deprivation and is correlated with intervening dream emotions

Rapid eye movement (REM) sleep and dreaming may be implicated in cross-night adaptation to emotionally negative events. To evaluate the impact of REM sleep deprivation (REMD) and the presence of dream emotions on a possible emotional adaptation (EA) function, 35 healthy subjects randomly assigned to REMD ( n  = 17; mean age 26.4 ± 4.3 years) and control ( n  = 18; mean age 23.7 ± 4.4 years) groups underwent a partial REMD and control nights in the laboratory, respectively. In the evening preceding and morning following REMD, subjects rated neutral and negative pictures on scales of valence and arousal and EA scores were calculated. Subjects also rated dream emotions using the same scales and a 10-item emotions list. REMD was relatively successful in decreasing REM% on the experimental night, although a mean split procedure was applied to better differentiate subjects high and low in REM%. High and low groups differed – but in a direction contrary to expectations. Subjects high in REMD% showed greater adaptation to negative pictures on arousal ratings than did those low in REMD% ( P  < 0.05), even after statistically controlling sleep efficiency and awakening times. Subjects above the median on EA_valence had less intense overall dream negativity ( P  < 0.005) and dream sadness ( P  < 0.004) than subjects below the median. A correlation between the emotional intensities of the morning dream and the morning picture ratings supports a possible emotional carry-over effect. REM sleep may enhance morning reactivity to negative emotional stimuli. Further, REM sleep and dreaming may be implicated in different dimensions of cross-night adaptation to negative emotions.     

Motor responsiveness to stimuli presented during sleep: the influence of time-of-testing on sleep stage analyses.

The relationship between time-of-night of testing (circadian factors) and motor responsiveness to stimuli presented during different stages of sleep was examined. Nine males slept for two nonconsecutive nights in the laboratory. On Night 1, tympanic temperature was assessed at 30 min intervals. On Night 2, responsiveness was assessed with an incremental series of tones presented in sleep stages 2, 3/4, and REM throughout the night. Subjects were instructed to make a microswitch closure to the tones. Results showed that for all stages, responsiveness decreased across thirds of the night. Because the distribution of each sleep stage differed across the night, the effects on responsiveness due to time-of-testing and to sleep stage were confounded. When time-of-testing was held constant, responsiveness was greater in stages 2 and REM than in stage 3/4. When time-of-testing was not held constant, effects nearly opposite of the latter could be demonstrated.     

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.     

Time‐of‐night variations in the story‐like organization of dream experience developed during rapid eye movement sleep

This study aimed to investigate the cycles (2nd/4th) and duration‐related (5/10 min) variations in the story‐like organization of dream experience elaborated during rapid eye movement (REM) sleep. Dream reports were analysed using story grammar rules. Reports were provided by those subjects (14 of 22) capable of reporting a dream after each of the four awakenings provoked in 2 consecutive nights during REM sleep of the 2nd and 4th cycles, after periods of either 5 or 10 min, counterbalanced across the nights. Two researchers who were blind as to the sleep condition scored the dream reports independently. The values of the indicators of report length (measured as value of total word count) and of story‐like organization of dream reports were matched taking time‐of‐night (2nd and 4th cycles) and REM duration (5 versus 10 min) as factors. Two‐way analyses of variance showed that report length increased significantly in 4th‐cycle REM sleep and nearly significantly for longer REM duration, whereas the number of dream‐stories per report did not vary. The indices of sequential (number of statements describing the event structure developed in the story) and hierarchical (number of episodes per story) organization increased significantly only in dream‐stories reported after 10 min of 4th‐cycle REM sleep. These findings indicate that the characteristics of structural organization of dream‐stories vary along with time of night, and suggest that the elaboration of a long and complex dream‐story requires a fairly long time and the availability of a great amount of cognitive resources to maintain its continuity and coherence.     

Effects of otolithic vestibular stimulation on sleep

This study evaluated the effects of otolithic vestibular stimulation in the form of a linearly accelerated parallel swing on nighttime sleep parameters and daytime sleep tendency in eight normal subjects. The protocol consisted of one adaptation night following by two motion nights, one adaptation night followed by two stationary nights, and two Multiple Sleep Latency Tests (MSLT), one motion and one stationary. On the motion nights, there was a decrease in stage 2 percentage as well as a facilitative effect on sleep latency on the last night. In addition, an increase in the number of rapid eye movements (REMs) per night was found without a significant alteration of REM sleep amount or latency. No significant differences were found between the motion and stationary MSLT days.     

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.     

Neuroticism and dreaming sleep: a case for interactionism in personality research.

The value of a trait approach to sleep and dreaming characteristics is evaluated by reviewing recent research on differential patterns and interactions manifest by high and low neuroticism subjects. Differential patterning of dream content and REM sleep characteristics under positive and negative presleep conditions suggest a qualitative difference in experience and behavior, and a quantitative difference in "importance" attributable to the dreaming sleep process. It is hypothesized that, under "normal" conditions, low neuroticism individuals make more exclusive use of the dreaming period, while under "artificial" conditions, they demonstrate a greater motivation to compensate for restricted REM by intensification of the REM process (shortened REM onset latencies, greater REM rebound, intensified dream experiences). Finally, it is suggested that theories of dreaming sleep should recognize the importance of traits, as well as situational factors to the psychology of dreaming sleep.     

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.     

Effect of a presleep optokinetic stimulation on rapid eye movements during REM sleep

Some evidence supports the view point that phasic motor events of REM sleep show a complementary relation with the corresponding wake motor activities: (a) an inverse relationship between waking saccades and REM sleep eye movements (REMs) has been found with respect to frequency, amplitude, and direction; (b) an increase of middle-ear muscle activity (MEMA) in the 2 h before sleep causes a complementary decrease of MEMA during REM sleep. The present study evaluated this relation with respect to the optokinetic (OKN) system, assessing the role of automatically induced eye movements in affecting direction and frequency of REMs during sleep. Ten subjects were recorded following standard rules in 3 consecutive nights (one adaptation, one baseline, one experimental). In the experimental night subjects underwent 2 h presleep OKN stimulation at 15 degrees /s. The actual mean number of quick phases of nystagmus induced by the OKN stimulation was 12461.4 +/- 1.7 quick phases/s). No significant effect was found with regard to direction or frequency of REMs; the hypothesis that differences in REM direction and frequency could be modulated by the rank order of REM episodes (i.e., as a function of time elapsed from presleep stimulation) also failed to show any effect of a complementary relation between OKN and REMs. The results suggest that the complementary relation between wake and sleep eye movements is specific for the saccadic system, allowing us to exclude a peripheral mechanism, that is, an effect due to fatigue of extraocular muscles.     

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.