Hockenbury Discovering Psychology 5th txtbk

156 CHAPTER 4 Consciousness and Its VariationsAn Episode of Cataplexy inNarcolepsy In this sequence ofimages, a man with narco lepsyexperiences one of its mostdramatic symptoms—cataplexy.Cataplexy involves the suddenand complete loss of muscletone, and it is typically triggeredby laughter, embarrassment, orsome other type of emotionalarousal. Although unable tomove, the person remainsconscious and aware of what isgoing on around him.But in more severe episodes of cataplexy, the person may completely lose muscle control,knees buckling as he or she collapses. Although unable to move or speak, theperson is conscious and aware of what is happening.Narcolepsy is a dyssomnia that occurs in every culture and ethnic group, andit affects males and females equally. Although nowhere near as common as insomniaor sleep apnea, narcolepsy affects about 1 person in every 2,000 inthe United States and Canada. Interestingly, prevalence rates vary by culture.For example, narcolepsy is much more common—about 1 in every600 people—in Japan. Compare that with Israel, where a prevalence rateof less than 1 out of every 500,000 people makes narcolepsy rare(Longstreth & others, 2007; Silber & others, 2002).Narcolepsy is considered a lifelong, chronic condition. The onset ofnarcolepsy can occur at any age, including very young children. Onsetusually occurs during adolescence or young adulthood, but thecondition often goes undiagnosed or is misdiagnosed for years. Althoughgenetics may play a role—about 10 percent of people withnarcolepsy have a relative with the same symptoms—most peoplewith the disorder have no family history of narcolepsy.Research points to multiple factors in the development of narcolepsy,including chromosomal, brain, neurotransmitter, and immunesystem abnormalities. Of note is the recent scientific discovery of a specialclass of neurotransmitters called hypocretins. Also called orexins,hypocretins are produced exclusively by neurons in the hypothalamus.These hypothalamus neurons actively produce hypocretins during thedaytime to maintain a steady state of wakefulness. When measured inspinal fluid, people with narcolepsy have very low or nonexistenthypocretin levels. Autopsies of people who had narcolepsy have revealedgreatly reduced numbers of hypocretin-producing neurons intheir brains (Datta & MacLean, 2007; Ohno & Sakurai, 2008).Although narcolepsy cannot yet be cured, various medicationscan help minimize symptoms. For example, modafinil (Provigil ® )and sodium oxybate (Xyrem ® ) are medications that reduce the excessivedaytime sleepiness experienced by people with narcolepsy(Kim & others, 2007). Antidepressant medications can help reduceepisodes of cataplexy, sleep paralysis, and unpleasant hallucinationsassociated with sleep onset or awakening fromsleep. Although they can be helpful, these medications are far from beinga panacea and, in fact, have potentially serious side effects (Thorpy, 2007).hypocretinsA special class of neurotransmitters producedduring the daytime to maintain asteady state of wakefulness.The ParasomniasUndesired Arousal or Actions During SleepThe parasomnias are a diverse collection of sleep disorders involving undesirablephysical arousal, behaviors, or events during sleep or sleep transitions (Mahowald &Schenck, 2005; Schenck, 2007). In the past, people were reluctant to discuss thesesleep disturbances, hence the parasomnias were long thought to be rare. But asyou’ll see in this section, collectively, the parasomnias are very common.Ranging from simple to very complex behaviors, each of the parasomniasinvolves some degree of waking arousal mixed with sleep. The person’s brain is justawake enough to carry out the actions yet is still so immersed in sleep that he or shehas no conscious awareness or subsequent memory of having performed the actions.Along with amnesia for the behaviors or events, other features tend to characterizethe parasomnias. As a general rule, parasomnias:• Arise during the NREM stages 3 and 4 slow-wave sleep that occurs in the firsthalf of the night.• Are more common in children and decrease with age.