Alien Abductions, Lucid Dreams, and Sleep Paralysis
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See http://code.pediapress.com/ for more information. PDF generated at: Sat, 22 Dec 2012 02:50:31 UTC Contents Articles Sleep paralysis 1 Alien abduction 11 Brian Dunning (author) 24 Hallucination 30 Schizophrenia 40 Epileptic seizure 55 Parasomnia 61 Hypnagogia 64 Night terror 72 References Article Sources and Contributors 77 Image Sources, Licenses and Contributors 80 Article Licenses License 81 Sleep paralysis 1 Sleep paralysis Sleep paralysis is a phenomenon in which people, either when falling asleep or wakening, temporarily experience a sense of inability to move, similar to when an arm or leg goes to sleep, but not associated with numbness. More formally, it is a transition state between wakefulness and rest characterized by complete muscle atonia (muscle weakness). It can occur at sleep onset or when awakening. It is believed a result of disrupted REM sleep, which is normally characterized by complete muscle atonia that prevents individuals from acting out their dreams. Sleep paralysis has been linked to disorders such as narcolepsy, migraines, anxiety disorders, and obstructive sleep apnea; however, it can also occur in isolation.[1][2] When linked to another disorder, sleep paralysis commonly occurs in association with the neuromuscular disorder narcolepsy.[2] Classification The two major classifications of sleep paralysis are isolated sleep paralysis (ISP) and recurrent isolated sleep paralysis (RISP). Of these two types ISP is much more common than RISP.[2] ISP episodes are infrequent and of short duration, approximately one minute. Sleep paralysis may only occur once in an individual's lifetime.[2] As the name suggests, recurrent isolated sleep paralysis is a chronic condition. The individual suffers from frequent episodes throughout their lifetime.[2] One of the major differences between ISP and RISP is duration. RISP episodes can last for up to an hour or The Nightmare, by Henry Fuseli (1781) is thought to be one of the classic longer, and have a much higher occurrence of depictions of sleep paralysis perceived as a demonic visitation. perceived out of body experiences—while ISP episodes are generally short (usually no longer than one minute) and are typically associated with the intruder and incubus hallucinations. ISP episodes can, however, persist for up to half an hour.[2] With RISP the individual can also suffer back to back episodes of sleep paralysis in the same night while this is unlikely in individuals who suffer from ISP.[2] It can be difficult to differentiate between cataplexy brought on by narcolepsy and true sleep paralysis, because the two phenomena are physically indistinguishable.[2] The best way to differentiate between the two is to note when the attacks occur most often. Narcolepsy attacks are more common when the individual is falling asleep; ISP and RISP attacks are more common on awakening.[3] Prevalence Isolated sleep paralysis is commonly seen in patients that have been diagnosed with narcolepsy. Approximately 30-50% of people that have been diagnosed with narcolepsy have experienced sleep paralysis as an auxiliary symptom.[1][4] The prevalence of sleep paralysis in the general population is approximately 6.2%. A majority of the individuals that have experienced sleep paralysis have sporadic episodes that occur once a month to once a year. Only 3% of individuals experiencing sleep paralysis that is not associated with a neuromuscular disorder have nightly episodes, as mentioned earlier, these individuals are diagnosed as having RISP.[1] Sleep paralysis is just as common for males as it is for females, however, different age groups have been found to be more susceptible to developing isolated sleep paralysis. Approximately 36% of the general population that experiences isolated sleep Sleep paralysis 2 paralysis is likely to develop it between 25 and 44 years of age.[1] Pathophysiology The pathophysiology of sleep paralysis has not been concretely identified, although there are several theories about what causes an individual to develop sleep paralysis. The first of these stems from the understanding that sleep paralysis is a parasomnia resulting from inappropriate overlap of the REM and waking stages of sleep.[5] Polysomnographic studies found that individuals with sleep paralysis had shorter REM sleep latencies than normal along with shortened NREM and REM sleep cycles, and fragmentation of REM sleep.[6] This study supports the observation that disturbance of regular sleeping patterns can instigate an episode of sleep paralysis, because fragmentation of REM sleep commonly occurs when sleep patterns are disrupted and has now been seen in combination with sleep paralysis.[6] Another major theory is that the neural bodies that regulate sleep are out of balance in such a way that allows for the different sleep states to overlap.[7] In this case, cholinergic sleep on neural populations are hyper activated and the serotonergic sleep off neural populations are under-activated.[7] As a result the cells capable of sending the signals that would allow for complete arousal from the sleep state, the serotonergic neural populations, have difficulty in overcoming the signals sent by the cells that keep the brain in the sleep state.[7] Normally during REM sleep the threshold for a stimulus capable of causing arousal is greatly elevated; however, in individuals with SP there is almost no blocking of exogenous stimuli, which means it is much easier for the individual to be aroused by a stimulus.[7] There may also be a problem with the regulation of melatonin, which under normal circumstances regulates the serotonergic neural populations.[2] Melatonin is typically at its lowest point during REM sleep.[2] Inhibition of melatonin at an inappropriate time would make it impossible for the sleep off neural populations to depolarize when presented with a stimulus that would normally lead to complete arousal.[2] This could explain why the REM and waking stages of sleep overlap during sleep paralysis, and definitely explains the muscle paralysis experienced on awakening.[2] If the effects of the sleep on neural populations cannot be counteracted, we retain characteristics of the REM stage of sleep once we have awoken. Research has found a genetic component in sleep paralysis.[8] The characteristic fragmentation of REM sleep, hypnopompic, and hypnagogic hallucinations have a heritable component in other parasomnias, which lends credence to the idea that sleep paralysis is also genetic.[9] Twin studies have shown that if one twin of a monozygotic pair experiences sleep paralysis that other twin is very likely to experience it as well.[9] The identification of a genetic component means that there is some sort of disruption of function at the physiological level. Further studies must be conducted to determine whether there is a mistake in the signaling pathway for arousal as suggested by the first theory presented, or whether the regulation of melatonin or the neural populations themselves have been disrupted. Signs and symptoms Physiologically, sleep paralysis is closely related to REM atonia, the paralysis that occurs as a natural part of REM (rapid eye movement) sleep. Sleep paralysis occurs either when falling asleep, or when awakening. When it occurs upon falling asleep, the person remains aware while the body shuts down for REM sleep, and it is called hypnagogic or predormital sleep paralysis. When it occurs upon awakening, the person becomes aware before the REM cycle is complete, and it is called hypnopompic or postdormital.[10] The paralysis can last from several seconds to several minutes, with some rare cases being hours, "by which the individual may experience panic symptoms"[11] (described below). As the correlation with REM sleep suggests, the paralysis is not entirely complete; use of EOG traces shows that eye movement is still possible during such episodes, however, the individual experiencing sleep paralysis is unable to speak.[12] Sleep paralysis 3 Hypnagogic and hypnopompic hallucinations are symptoms commonly experienced during episodes of sleep paralysis. Some