SLEEP DISORDERS 
The recognition of rapid eye movement (REM) sleep in the 1950s (Dement, 1994) created an 
outpouring of research in cats and rats, in particular, that led to the development of a new 
branch of clinical medicine devoted to the diagnosis and treatment of sleep disorders 20 years 
later. The research on animals has greatly advanced understanding of the neural mechanisms 
underlying this extraordinary behavior in which the brain activity resembles that of alert 
wakefulness while the body musculature is paralyzed. Efforts to understand the latter 
ultimately led to the recognition and successful treatment of REM Behavior Disorder, in which 
the paralysis is overcome and people act out their dreams, which often results in serious 
bodily harm (Morrison, 1996). 
The sleep disorder narcolepsy involves a disturbance of motor control and afflicts 0.05 percent 
of the population in the United States. Patients suffer from continual sleepiness and a strong 
tendency to experience partial to complete paralysis of their skeletal muscles while awake 
when presented with various emotion-laden stimuli or situations. There is no adequate 
treatment to relieve their misery. Genetic studies using dogs with a naturally occurring form 
of this disease, in which the sleep behavior has been studied for many years, and with mice 
have led to a recent breakthrough of identifying specific genes. These genes helped point 
researchers to a small collection of neurons utilizing peptides known as hypocretins in the 
hypothalamus. The connections of these neurons with other neurons long implicated in the 
regulation of sleep and wakefulness suggested that defects in their functioning could lead to 
various symptoms of narcolepsy, such as excessive sleepiness and cataplexy (Kilduff and 
Peyron, 2000). These studies led to the examination of the brains of narcoleptics, with the 
exciting result that very significant loss of the hypocretin neurons was found (Peyron et al., 
2000; Thannickal et al., 2000). This was the first demonstration of a specific anatomical 
defect in this disorder. These findings are the first step in the development of targeted drugs 
that could help relieve the debilitating symptoms associated with the disorder. 
In addition to specific sleep disorders, sleep loss, for a variety of reasons (many of which are 
linked to the hectic pace of modern life), can have a severe impact on human health and 
productivity (Kilduff and Kushida, 1999). Basic research on the mechanisms and genetics of 
circadian and homeostatic control of sleep may lead to a more complete understanding of the 
causes and effects of sleep loss. For instance, research encompassing a wide range of life 
forms, including bacteria, yeast, fruit flies, rodents, and humans (Dunlop, 1999; Johnson and 
Golden, 1999), has shed light on topics ranging from plant growth to understanding sleep 
patterns in animals and humans, which, in turn, has helped us better understand jet lag, shift 
work, and drowsy driving (Moore-Ede et al., 1982). ■ 
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