Relations among hypnagogic and hypnopompic experiences associated with sleep paralysis.
The Waterloo Sleep Experiences Scale was developed to assess the prevalence of sleep paralysis and a variety of associated hypnagogic and hypnopompic hallucinoid experiences: sensed presence, felt pressure, floating sensations, auditory and visual hallucinations, and fear. Consistent with results of recent surveys, almost 30% of 870 university students reported at least one experience of sleep paralysis. Approximately three-quarters of those also reported at least one hallucinoid experience, and slightly more than 10% experienced three or more. Fear was positively associated with hallucinoid experiences, most clearly with sensed presence. Regression analyses lend support to the hypothesis that sensed presence and fear are primitive associates of sleep paralysis and contribute to the elaboration of further hallucinoid experiences, especially those involving visual experiences. (+info)
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. (+info)
Situational factors affecting sleep paralysis and associated hallucinations: position and timing effects.
Sleep paralysis (SP) entails a period of paralysis upon waking or falling asleep and is often accompanied by terrifying hallucinations. Two situational conditions for sleep paralysis, body position (supine, prone, and left or right lateral decubitus) and timing (beginning, middle, or end of sleep), were investigated in two studies involving 6730 subjects, including 4699 SP experients. A greater number of individuals reported SP in the supine position than all other positions combined. The supine position was also 3-4 times more common during SP than when normally falling asleep. The supine position during SP was reported to be more prevalent at the middle and end of sleep than at the beginning suggesting that the SP episodes at the later times might arise from brief microarousals during REM, possibly induced by apnea. Reported frequency of SP was also greater among those consistently reporting episodes at the beginning and middle of sleep than among those reporting episodes when waking up at the end of sleep. The effects of position and timing of SP on the nature of hallucinations that accompany SP were also examined. Modest effects were found for SP timing, but not body position, and the reported intensity of hallucinations and fear during SP. Thus, body position and timing of SP episodes appear to affect both the incidence and, to a lesser extent, the quality of the SP experience. (+info)
Narcolepsy in Singapore: is it an elusive disease?
INTRODUCTION: The aims of the study were to determine the demographic, clinical, and polysomnographic characteristics of narcolepsy, and to address the difficulties in diagnosing narcolepsy and cataplexy, which is a cardinal symptom. We also ventured to investigate the differences between narcolepsy with and without cataplexy. MATERIALS AND METHODS: Data were collected retrospectively from patients diagnosed with narcolepsy at the Sleep Disorder Unit of Singapore General Hospital over 5 years. Each patient had had a detailed clinical evaluation and overnight polysomnography (PSG) followed by a multiple sleep latency test (MSLT). RESULTS: A total of 28 cases were studied. Males made up 85.7% of the total and females, 14.3%. The mean age was 30.9 years. All had excessive daytime sleepiness. Other manifestations were cataplexy (48.1%), sleep paralysis (51.9%), hypnogogic hallucinations (84%), disturbed night sleep (29.2%), automatisms (17.4%) and catnaps (95.8%). The mean duration of symptoms was 7.24 years. In the MSLT, the mean values for mean sleep latency and number of sleep onset rapid eye movement (REM) periods (SOREMP) were 4.3 minutes and 2.7, respectively. Narcolepsy was associated with obstructive sleep apnoea and periodic limb movement disorder (35.7%). All the variables were compared between those who had narcolepsy with cataplexy and without cataplexy. The duration of presenting complaint, REM latency, respiratory disturbance index, number of SOREMPs and the presence of sleep paralysis were significantly different in the 2 groups. CONCLUSIONS: Narcolepsy predominantly affects young males. Concurrence of other sleep disorders is not uncommon. Some differences are evident between those who have narcolepsy with and without cataplexy. (+info)
Sleep paralysis episode frequency and number, types, and structure of associated hallucinations.
Sleep paralysis (SP) episodes are often accompanied by vivid hallucinoid experiences that have been found to fall into three major categories thought to be organized according to intrinsic rapid eye movement (REM) processes. Prior research has, however, combined data for individuals with varying degrees of experience with SP episodes, rendering interpretations of the source of this structure ambiguous. The present study of 5799 current SP experients compares the nature and structure of the hallucinations of novice SP experients with those reporting varying numbers of episodes. Both qualitative and quantitative differences were found in reported hallucinations as a function of episode frequency, although the underlying three-factor structure of the hallucinoid experiences was highly similar for all groups. Novice experients' reports were, however, characterized by clearer differentiation of factors, likely because of a tendency of experienced SP experients to conflate experiences across episodes. Age and age of onset of SP episodes were associated with differences in the variety and types of hallucinations but not their underlying structure. Earlier onset of SP episodes was also associated with more frequent episodes. The results are consistent with the hypothesis that the basic form and patterning of hallucinatory experiences is a result of intrinsic processes, independent of prior experience, likely associated with underlying REM neurophysiology. (+info)
Timing of spontaneous sleep-paralysis episodes.
The objective of this prospective naturalistic field study was to determine the distribution of naturally occurring sleep-paralysis (SP) episodes over the course of nocturnal sleep and their relation to bedtimes. Regular SP experiencers (N = 348) who had previously filled out a screening assessment for SP as well as a general sleep survey were recruited. Participants reported, online over the World Wide Web, using a standard reporting form, bedtimes and subsequent latencies of spontaneous episodes of SP occurring in their homes shortly after their occurrence. The distribution of SP episodes over nights was skewed to the first 2 h following bedtime. Just over one quarter of SP episodes occurred within 1 h of bedtime, although episodes were reported throughout the night with a minor mode around the time of normal waking. SP latencies following bedtimes were moderately consistent across episodes and independent of bedtimes. Additionally, profiles of SP latencies validated self-reported hypnagogic, hypnomesic, and hypnopompic SP categories, as occurring near the beginning, middle, and end of the night/sleep period respectively. Results are consistent with the hypothesis that SP timing is controlled by mechanisms initiated at or following sleep onset. These results also suggest that SP, rather than uniquely reflecting anomalous sleep-onset rapid eye movement (REM) periods, may result from failure to maintain sleep during REM periods at any point during the sleep period. On this view, SP may sometimes reflect the maintenance of REM consciousness when waking and SP hallucinations the continuation of dream experiences into waking life. (+info)
CSF hypocretin-1 levels and clinical profiles in narcolepsy and idiopathic CNS hypersomnia in Norway.
OBJECTIVE: To evaluate the relationship between CSF hypocretin-1 levels and clinical profiles in narcolepsy and CNS hypersomnia in Norwegian patients. METHOD: CSF hypocretin-1 was measured by a sensitive radioimmunoassay in 47 patients with narcolepsy with cataplexy, 7 with narcolepsy without cataplexy, 10 with idiopathic CNS hypersomnia, and a control group. RESULTS: Low hypocretin-1 values were found in 72% of the HLA DQB1*0602 positive patients with narcolepsy and cataplexy. Patients with low CSF hypocretin-1 levels reported more extensive muscular involvement during cataplectic attacks than patients with normal levels. Hypnagogic hallucinations and sleep paralysis occurred more frequently in patients with cataplexy than in the other patient groups, but with no correlation to hypocretin-1 levels. CONCLUSION: About three quarters of the HLA DQB1*0602 positive patients with narcolepsy and cataplexy had low CSF hypocretin-1 values, and appear to form a distinct clinical entity. Narcolepsy without cataplexy could not be distinguished from idiopathic CNS hypersomnia by clinical symptoms or biochemical findings. (+info)
'The devil lay upon her and held her down'. Hypnagogic hallucinations and sleep paralysis described by the Dutch physician Isbrand van Diemerbroeck (1609-1674) in 1664.