Sleep-onset REM periods

Sleep-wake state alterations in PD can be broadly classified into disturbances of (1) thalamocortical arousal state and (2) excessive nocturnal movement (Rye and Bliwise 2004 Rye and Iranzo 2005). The former includes the loss of sleep spindles and SWS, daytime sleepiness, and intrusion of REM sleep into daytime naps (i.e. sleep onset REM periods, or SOREMs), and the latter encompass periodic leg movements of sleep (PLMs) and REM sleep behavior disorder (RBD). The pathophysiological basis of sleepiness and SOREMs appears to be dopaminergic cell loss in PD, though excessive nocturnal movements are not as clearly related to dopaminergic deficits. 

Abnormal sleep-onset REM periods, which occur within 15 min of sleep onset, are of major importance in the diagnosis of narcolepsy. Other causes of sleep-onset REM periods, such as sleep deprivation or other sleep disorders (e.g., obstructive sleep apnea), must be excluded (28). 

Sleepiness is a primary symptom of narcolepsy, often preceding the onset of the other well-known symptoms of the disease, namely cataplexy, sleep paralysis, and hypnagogic hallucinations (44). Evaluation of the MSLT of narcoleptic patients has demonstrated a short sleep latency (<5 min) and multiple sleep-onset REM periods (SOREMPs). The more specific finding in the MSLT of narcoleptic patients is more than 2 SOREMPs, shown to reach a specificity of 99% by Amira et al. (45), which further increased to 99.2% if 3 SOREMPs were recorded (46). On the other hand, more than one SOREMP can occur in nonnarcoleptic patients, such as those with sleep apnea, sleep deprivation, depression, periodic limb movements, circadian rhythm disruption, or withdrawal from REM-suppressing medications (5,47). Thus, the findings of the MSLT, which is always performed for suspected narcoleptic patients, must be interpreted in view of the clinical history and nocturnal PSG. 

Fukuda K, Miyasita A, Inugami M. Sleep onset REM periods observed after sleep interruption in normal short and normal long sleeping subjects. Electroencephalogr Clin Neurophysiol 1987 67 508-513. 

The word narcolepsy refers to a syndrome of unknown origin that is characterized by abnormal sleep tendencies, including excessive daytime sleepiness and often disturbed nocturnal sleep and pathological manifestations of REM sleep. The REM sleep abnormalities include sleep onset REM periods and the dissociated REM sleep inhibitory processes, cataplexy and sleep paralysis. Excessive daytime sleepiness, cataplexy, and less often sleep paralysis and hypnagogic hallucinations are the major symptoms of the disease [12]. 

To answer this question we need to look more closely at the sleep side of depression. There are three parts to the main story. The first is that many depressives have a markedly reduced time to onset of the first REM period after falling asleep. This tendency to enter REM rapidly is measured as REM latency. The second part is that depressives may also have a marked reduction in time spent in stages III and IV, the deepest and most restful phase of NREM sleep. That could be one reason that their sleep is so unrefreshing. The third reason is that the first REM period is often longer—and stronger—than is seen in age and sex matched normal controls. These processes are represented in terms of the AIM state space model as figure 11.1. 

Fig. 1. Schematized hypnogram demonstrating most of the sleep disorders described in the literature using laboratory recordings of untreated persons with schizophrenia. One category of sleep disorders in schizophrenia is the insomnia type , with long sleep latency, numerous and/or long awakenings, and short sleep duration. Another type of sleep disorders is more concerned with sleep organization, e.g.., short duration of SWS and/or short latency to the onset of REM sleep. Not all disorders are found in every study since variables such as symptoms or diagnosis subtype, severity and chronicity may influence the results (see text). REMS, REM sleep. A REM sleep period is defined as a succession of REM sleep epochs not interrupted for more than 15 min.

Many depressed patients experience an earlier onset of REM during the first sleep cycle. The first REM period may also last longer and be more intense than normal. The process is reversed by antidepressant medications that strengthen the aminergic and weaken the cholinergic systems. 

L9 Neurotransmitters and REM Sleep In Humans. Neurotransmitters have both a direct and indirect action on REM sleep. The indirect action is manifested by a self-inhibitory feed back mechanism (Equation 5.5). Cholinergic transmission (acetylcholine)activate neurons in their pontine reticular formation (PRF) and produce REM sleep. REM sleep gradually activates REM-ofif monoamin-ergic neurons, which produce a self-inhibitory feedback and eventually terminates REM sleep. As the REM sleep period changes to NREM sleep, the REM-off neuronal activity gradually decreases during NREM sleep, and. is at minimum at the onset of REM sleep. 

Beginning 90 minutes after the onset of sleep, there are periods of intense mental activity during which the closed eyes jerk around under their lids. Persons who were awakened during REM sleep report that they had been dreaming. The first REM period lasts about 10 minutes, and, with each subsequent 90-minute period, the REM period eventually takes up 20-25% of total sleep time. Dreaming is not limited to REM periods. People often recall dreams shortly after falling asleep, during a period of non-REM sleep. 

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