Answer to Question 1
They include nightmares (repeated awakenings, with frightening dreams that you usually remember), sleep terrors (abrupt awakening, accompanied by autonomic arousal but no recall), and sleepwalking (getting out of bed and walking around, but with no recall the next day). Nightmares occur during rapid-eye-movement (REM) (dream) sleep, usually during the second half of the sleep period, whereas sleep terrors and sleep walking occur during non-REM (NREM) sleep (for this reason, DSM-5 combines sleep terrors and sleepwalking into one category: NREM sleep arousal disorders). Sleep terrors and sleepwalking occur during deep sleep in the first third of the sleep cycle, when the person is so soundly asleep that he or she is difficult to arouse and has no recall of the episode the next morning (Reid et al., 2009).
Answer to Question 2
Dyssomnias are disorders of initiating or maintaining sleep, characterized by difficulty getting enough sleep, not sleeping when you want to, not feeling refreshed after sleeping, and so forth. Parasomnias, in contrast, are sleep disorders in which behavioral or physiological events intrude on ongoing sleep. Whereas dyssomnias involve disruptions in the sleep process, parasomnias involve physiological or cognitive arousal at inappropriate times during the sleepwake cycle, which can result in sleepwalking or in nightmares that jolt someone from sleep. Persons suffering from parasomnia sleep disorders often report unusual behaviors while asleep, rather than sleepiness or insomnia.
A Subject Prepared for a Night’s Sleep in a Sleep Laboratory
Why your body loves sleep
National Sleep Foundation Survey Results
Four pieces of evidence that the reticular formation is involved in sleep.
Characteristics of NREM and REM sleep
Typical Night’s Sleep for a Young Adult