Sleep position and sleep stages: evidence of their independence.

Recently we conducted a first ontogenetic study of sleep positions in the human, which involved five groups of 10 subjects (5 males, 5 females) from each of the following age categories: 3-5 years, 8-12 years, 18-24 years, 35-45 years, 65-80 years. They slept for 4 consecutive nights in the laboratory. Sleep positions were recorded during 2 nights with super-8 time-lapse photography. In a first report we presented results showing developmental trends in sleep position shifts, position durations and in the use of prone, supine and side positions. In the current report we present results showing that there was no significant relationship between sleep stages and sleep positions in any group. Furthermore, time-series analyses revealed no consistent pattern of position sequences in any of the age groups. It is concluded that, while there are ontogenetic trends in sleep position preferences, sleep positions are independent of sleep stages and do not show consistent rhythmicity.

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 degrees) 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.

Sleep positions and position shifts in five age groups: an ontogenetic picture.

In an attempt to characterize the development of sleep positions and position shifts in the human, 10 subjects (5 males and 5 females) in each of the following five age groups were studied: 3-5, 8-12, 18-24, 35-45 and 65-80 years old. Subjects slept for four consecutive nights (except the 3-5 year olds who slept two nights) in the laboratory where standard polysomnography was recorded. On nights 3 and 4, sleep positions were recorded with a Super 8 Camera taking one frame every 8 seconds and were scored using four dimensions (head, trunk, legs and arms) each consisting of four categories. The results revealed a significant ontogenetic decrease in the number of position shifts with averages of 4.4, 4.7, 3.6, 2.7 and 2.1 changes per hour, respectively. There was a corresponding progressive increase in the duration of positions and in the number of periods of more than 30 minutes of postural immobility. Whereas in children, prone, supine and lateral positions were assumed to occupy an equal proportion of sleep time, trend analyses revealed a significant progressive ontogenetic disappearance of prone positions and a progressive preference, very marked in the elderly, for right-side positions.

[Biological rhythms associated with sleep and psychological adjustment]. / Les rythmes biologiques liés au sommeil et l'adaptation psychologique.

Because of their influence on psychological adaptation, biological rhythms associated with sleep have received growing attention during the last two decades. We are presenting an outline of (1) the ultradian rhythms of rapid-eye-movement (REM) sleep and of slow wave sleep (SWS), (2) the circadian rhythms of sleep/wake, body temperature and melatonine secretion, and (3) the infradian rhythms of the menstrual cycle and seasonal affective disorders emphasizing their importance in psychological adaptation. Particular attention is given to the consequences of the desynchronization of the circadian phase of sleeping and waking with that of core body temperature observed in the cases of abrupt time zone changes, shift work and some forms of insomnia and depression. New methods of intervention, such as the use of exposure to bright lights are discussed. A case is made for increased attention to a new form of hygiene, that of the biological rhythms associated with sleeping and waking.

Presleep suggestion related to a phobic object: successful manipulation of reported dream affect.

Twenty-four female subjects with a strong dislike of snakes slept for four nonconsecutive nights in the laboratory. They were divided into four groups of six, each group receiving a different presleep suggestion on Nights 3 and 4. On Nights 2, 3, and 4, before sleep, the subjects saw but did not have to touch a live snake and their dreams were collected for each REM period. The results showed that, when compared with the subjects who received the negative affect suggestions, subjects who received positive affect suggestions had significantly higher levels of positive emotions in their dreams, rated their own dreams as more pleasant, and had significantly lower levels of anxiety, sadness, and aggression. These results support the hypothesis that presleep suggestion can be an effective technique in influencing the affective dimension of the dream.

[Paradoxical sleep and information processing: exploration by inversion of the visual field]. / Le sommeil paradoxal et le traitement de l'information: une exploration par l'inversion du champ visuel.

The purpose of this study was to test the potential relationship between REM sleep and information processing with inversion of the visual field. In the 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, and 6 of each session, the subjects wore glasses which, during the second session, completely inverted (rotation of 180 degrees) 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 a second time. When the data of the two experiments were combined, there was a significant (p less than .01) increase in the percentage of REM sleep from Nights 3 and 4 of the control condition to Nights 3 and 4 of the visual inversion condition, but there was no significant change in any of the other sleep stages. There was a significant decrease in horizontal (p less than .04) and vertical (p less than .005) REM density and in the density of vertical REM bursts (p less than .02). The increase in REM sleep supports the hypothesis that REM sleep contributes to information processing while the decrease in REM density suggests that this component of REM sleep may be involved in a homeostatic process of sensory input.

Language learning efficiency, dreams and REM sleep.

As a follow-up from a previous study, four subjects taking a 6-week French language immersion program maintained a dream diary starting 2 weeks before until 2 weeks after the course. They also slept in the laboratory during four series of nights: one before the course, two during the course and one after the course. Confirming previous observations, it was observed that those subjects who made significant progress in French learning, experienced French incorporations into dreams earlier and had more verbal communication in their dreams during the language training than those who made little progress. Combining these results with those of the earlier study revealed significant positive correlations between language learning efficiency and both increases in REM sleep percentages, and verbal communication in dreams, as well as a negative correlation with latency to the first French incorporation in dreams. These results support the notion that REM sleep and dreaming are related to waking cognitive processes.

Intensive language learning and increases in rapid eye movement sleep: evidence of a performance factor.

Ten anglophone students taking a 6-week French immersion course were recorded in the sleep laboratory during 4 consecutive nights before the course, during the course and after the course. There was a positive and significant (P less than 0.05) correlation between language learning efficiency and increases in the percentage of rapid eye movement (REM) sleep from pre-course to course periods. This observation suggests that learning performance may be an important factor in the relationship between information processing and REM sleep.

Steroid treatment in acute ischaemic stroke. A comparative retrospective study of 556 cases.

The files of 556 patients with a history of ischaemic stroke were reviewed. The disability and mortality rates were compared between 277 patients with a steroid treatment in the acute stage and 279 without. Comparison of the whole group showed that the steroid-treated patients had less improvement of their disability and a higher mortality rate than the non-steroid group. However, in the former more patients with a severe stroke were present. Statistical analysis of a subset of 208 patients with completed stroke in the middle cerebral artery territory showed no marked difference in the outcome and the adverse reactions between the steroid- and non-steroid-treated patients.

Sleep positions and postural shifts in elderly persons.

The sleep characteristics and the body positions of four men and four women ranging in age from 65 to 75 yr. were monitored in the laboratory for 2 consecutive nights preceded by 2 adaptation nights. Overall, there was an average of 16 position shifts per night with duration of position averaging 33 min. The preferred trunk positions were on the right side (55%) and the least frequent on the stomach (2%) and limited to waking episodes. Back positions occurred for 19% of sleeptime and left positions for 22%. The preference for the right side and the absence of stomach postures during sleep which appear to be characteristic of elderly persons may respectively be related to cardiovascular and respiratory functions.

Are REM cycles in narcoleptic patients governed by an ultradian rhythm?

Twelve narcoleptic subjects experiencing at least five daytime REM sleep episodes were monitored for 34 consecutive hours in the laboratory starting at 2200 h one evening and ending at 0800 h a day and a half later. There was no significant difference between the length of the daytime and nighttime REM cycles. To test the hypothesis that an underlying rhythm governs REM episodes, a grid was constructed on the basis of the mean and the SD of the daytime cycles (starting at 0800 h the first morning) was projected on the following nighttime and its correspondence with actual night cycles was evaluated. Overall, it was observed that the number of night cycles falling within the projected grid was significantly higher than chance (p less than 0.01), indicating that nighttime REM episodes tended to fall within the same periodicity as their preceding daytime episodes. This observation supports the hypothesis that an underlying basic rest-activity cycle governs REM sleep episodes in narcoleptic subjects.

Daytime sleep characteristics and their relationships with night sleep in the narcoleptic patient.

Thirty-six narcoleptic patients with overwhelming sleep episodes, cataplexy, and sleep onset REM (SOREM) episodes were recorded for 34 continuous hours in the laboratory starting at 2200 h and ending at 0800 h a day and a half later. There were 94 SOREM and 60 sleep onset NREM (SONREM) episodes. While SONREM episodes were evenly distributed across daytime, SOREM episodes peaked between 0800 and 1000, 1200 and 1400, and 1600 and 1800 h. The ratio of SOREM to SONREM episodes was at its highest level between 1200 and 1400 h. Correlation coefficients between night 1 and night 2 for total sleep time (TST) and percentages of sleep stages were all positive and significant, whereas between daytime and each night, they were significant for percentages of stages 1, 2, and REM. Sleep-stage distribution across the last 24 h of continuous recording indicated that although TST levels were higher than that typical of normal subjects, REM sleep and slow wave sleep followed the same circadian distribution as that observed in normal subjects. The results are interpreted as evidence that the daytime sleep of narcoleptic patients is modified, similar to their night sleep, and that SOREM episodes are influenced by a time-of-day effect which culminates between 1200 and 1400 h.

Sleep, dreaming, and adaptation to a stressful intellectual activity.

Sixteen male subjects slept in the laboratory for 4 consecutive nights. Night 1 was an adaptation night and night 2 was a baseline night of uninterrupted sleep. On nights 3 and 4 subjects were asked to complete "intelligence" tests prior to sleep. One half of the subjects attempted to complete difficult versions of "intelligence" tests without knowing that they could not be completed in te time allotted. The other subjects were given easier versions of the same tests that they were able to complete in the time allotted. Night 3 was a night of uninterrupted sleep and night 4 involved REM period awakenings for the purpose of dream collection. Stressful manipulation consisted of telling the subjects before the administration of either set of tests that an average university student should complete most of the items within the allotted time. On night 3 both groups showed a significant increase in sleep latency and a significant decrease in REM density compared to the baseline night. On night 4 subjects in the difficult condition experienced significantly more anxiety in their dreams and somewhat higher levels of incorporation of the presleep material than subjects in the easy condition. Our findings suggest that following a stressful experience uninterrupted sleep has more short term adaptive value than a procedure which enhances dream recall and that subjects who incorporate elements from a presleep stressful event into their remembered dreams show less adaptation on awakening than subjects who do not.

Reappearance of electroencephalogram slow waves in extended sleep with delayed bedtime.

A three-part study using prolonged nights of sleep was undertaken to verify Broughton's hypothesis of an approximate 12-h ultradrian rhythm of human slow wave sleep (SWS). Part I consisted of 2 8-h adaptation nights followed by a prolonged 15-h night of sleep with bedtime at midnight. A significant return of SWS occurred 12 h and 32 min after the first appearance of SWS. In part II, after 1 adaptation night, subjects were asked to sleep for 15 h but bedtime was delayed until 0400 h. A two-peak return of SWS was observed with a first significant return at 1228 h and a second significant return at 1745 h (i.e., 13 h and 32 min after the first appearance of SWS). In part III, bedtime was again delayed to 0400 h; but subjects were given 3 nights to adapt before the 15 h extended sleep. A single significant return of SWS was then observed at 1656 h, i.e., 12 h and 24 min after the first appearance with no peaks around 1200 h, thus exhibiting the same pattern as in part I. These results suggest that the return of SWS seen normally between 1200 and 1500 h is relatively well entrenched since it remained present in the extended night following sudden bedtime delay. It appears, moreover, that SWS does follow a bimodal 12-h rhythm, which is seen immediately upon extended delayed sleep and can be fully phase-shifted with habituation.

Reappearance of EEG slow waves in extended sleep.

The log of the amplitude of EEG waves during NREM sleep is a linear function of the log of their frequency. The slope of this function is reliable within individuals, is significantly less steep in elderly than in young subjects and, in both groups, becomes flatter across successive NREM periods. We interpret these results as consistent with the hypothesis that the function of NREM sleep is to reverse the effects of waking on the brain. According to this model the decreased steepness of slope in the elderly and in later NREM periods reflects the diminishing intensity of these processes. Whatever the correct interpretation, the within-subject consistency of slope values permits their empirical study as a function of experimental manipulations. In addition, the quantitative F-A function established here (A = c/Fb) sets constraints that may prove useful for physiologic models of EEG waves during sleep.

Sleep positions in the young adult and their relationship with the subjective quality of sleep.

The sleep characteristics and the body positions of eight good and eight poor sleepers were monitored in the laboratory for 2 consecutive nights preceded by 2 adaptation nights. Throughout the nights, sleep positions and sleep motility were monitored with a super-8 camera, and a new scoring method was used. Overall, the findings supported earlier observations regarding sleep positions and sleep motility. Interestingly, poor sleepers spent more time awake and had more awakenings than good sleepers. Consistently, poor sleepers spent more time on their backs with their heads straight. These results suggest that sleep positions constitute an important sleep variable and that they may be related to the quality of sleep.

Field dependence and the effect of REM deprivation on thirst.

Recently a number of studies have concerned the possible function of rapid eye movement (REM) sleep and the mastery of stress. The present study was designed to explore the possibility that REM sleep might play a function in reducing the potency of a stressful physiological stimulus, thirst, as well as the possibility that such a function might be specific to individuals falling at different points along the field-dependence dimension. While there was no difference between REM deprivation and non-REM awakening nights in subsequent morning thirst, there was a significant interaction between field dependence and night on morning thirst measures for 10 college students. These results are discussed in light of previous work on stylistic differences in dreaming and their possible role in adaptation to stress.